Äîêóìåíò âçÿò èç êýøà ïîèñêîâîé ìàøèíû. Àäðåñ îðèãèíàëüíîãî äîêóìåíòà : http://www.atnf.csiro.au/computing/software/gipsy/installation/manual.ps Äàòà èçìåíåíèÿ: Tue Aug 17 14:16:14 1999 Äàòà èíäåêñèðîâàíèÿ: Sat Jan 17 00:59:48 2009 Êîäèðîâêà: Ïîèñêîâûå ñëîâà: aurora

GIPSY User Guide
(Version 2.0 of July 1, 1992)
KAPTEYN ASTRONOMICAL INSTITUTE
SPACE RESEARCH ORGANIZATION of the NETHERLANDS
EXPERTISE CENTRE ASTRONOMICAL IMAGE PROCESSING
c
fl1992

Contents
1 Introduction 1
I Using GIPSY 3
2 Getting started 5
2.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5
2.2 Preparation : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5
2.3 The basic commands : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 5
2.4 GIPSY data sets : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 8
2.4.1 Sets and subsets : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 8
2.4.2 Specifying a position in a (sub)set : : : : : : : : : : : : : : : : : : : : : : 9
2.4.3 Specifying an area : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 9
2.5 A sample GIPSY session : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 10
2.6 Bug handling in Gipsy : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 11
2.7 News : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 11
3 Input syntax 12
3.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 12
3.2 Input of structures and substructures : : : : : : : : : : : : : : : : : : : : : : : : 12
3.3 Input of floating point or integer numbers : : : : : : : : : : : : : : : : : : : : : : 15
3.4 Input of logicals : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 16
3.5 Input of character strings : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 17
3.6 Input of coordinates : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 17
4 Hermes 21
4.1 What is Hermes? : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 21
4.2 Tasks : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 21
4.3 User input : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 22
4.3.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 22
4.3.2 Parameter syntax : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 23
4.3.3 Numerical input : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 24
4.4 Task context : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 24
4.5 tHermes : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 24
i

ii
4.5.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 24
4.5.2 User Command Area : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 25
4.5.3 Task Status Area : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 26
4.5.4 Common Output Area and Log File : : : : : : : : : : : : : : : : : : : : : 26
4.5.5 Running Tasks : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 27
4.5.6 Unix shell : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 29
4.6 xHermes : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 29
4.7 nHermes : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 29
4.7.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 29
4.7.2 Syntax : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 30
5 General GIPSY programs 33
5.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 33
5.2 Getting data into GIPSY : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 33
5.3 What is on disk? : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 36
5.4 Displaying data : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 42
5.5 Plotting data : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 44
5.6 Printing data : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 59
5.7 Statistics : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 59
5.8 Manipulating sets : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 60
5.9 Combining sets : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 63
5.10 Saving sets : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 65
6 Reducing radio data 66
6.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 66
6.2 General radio applications : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 66
6.3 WSRT specific applications : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 66
6.4 VLA specific applications : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 66
7 IRAS reduction 67
7.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 67
7.2 IRAS : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 67
7.2.1 Instrument and mission : : : : : : : : : : : : : : : : : : : : : : : : : : : : 67
7.2.2 IRAS data products : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 70
7.2.3 Pointing reconstruction : : : : : : : : : : : : : : : : : : : : : : : : : : : : 70
7.2.4 Timing : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 70
7.3 IRAS data in GIPSY: IRDS : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 71
7.3.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 71
7.3.2 Data structure description : : : : : : : : : : : : : : : : : : : : : : : : : : : 72
7.3.3 IRDS headers : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 74
7.4 IRAS reduction programs : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 74
7.4.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 74
7.4.2 Getting IRAS data into GIPSY : : : : : : : : : : : : : : : : : : : : : : : : 74
7.4.3 Inspecting raw IRAS data : : : : : : : : : : : : : : : : : : : : : : : : : : : 76

iii
7.4.4 Calibration of survey data : : : : : : : : : : : : : : : : : : : : : : : : : : : 77
7.4.5 Map making : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 77
7.4.6 Calibration of LRS data : : : : : : : : : : : : : : : : : : : : : : : : : : : : 77
8 Advanced use of GIPSY 79
8.1 Recall files : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 79
8.2 Default files : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 79
8.3 GIPSY in batch mode : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 80
8.4 COLA FILES : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 80
8.4.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 80
8.4.2 Cola syntax : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 81
8.4.3 Cola statements : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 83
8.5 Using different machines : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 85
8.6 Programming in GIPSY : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 85
II The GIPSY architecture 87
9 System architecture 89
9.1 Introduction : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 89
9.2 History : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 89
9.3 X Window : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 90
9.4 System architecture : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 91
9.5 HERMES : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 91
9.6 GIPSY and X11 : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 93
9.7 Database : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 93
9.8 Database interface: GIPSY database subsystem : : : : : : : : : : : : : : : : : : : 96
9.9 User interface : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 96
9.10 Control interface : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 97
9.11 Display interface : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 97
9.12 Plot interface: PGPLOT : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 97
9.13 Application programs : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 97
A GIPSY commands 100
A.1 Keyword syntax : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 100
A.2 List of GIPSY tasks : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 100
B Sky Projections used in GIPSY 104
B.1 Aitoff equal area projection : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 105
B.2 Equivalent Cylindrical projection : : : : : : : : : : : : : : : : : : : : : : : : : : : 105
B.3 Flat projection : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 105
B.4 Gnomonic projection : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 105
B.5 Orthographic projection : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 106
B.6 Rectangular projection : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 106
B.7 Global Sinusoidal projection : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 106

iv
B.8 North Celestial Pole projection : : : : : : : : : : : : : : : : : : : : : : : : : : : : 106
B.9 Stereographic projection : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 106
B.10 Mercator projection : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 107
C GIPSY files 108
C.1 Important files : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 108
C.2 Where are they? : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 108
D Host computer and operating system 109
E Hardware requirements 110

Chapter 1
Introduction
What is GIPSY?
GIPSY is an acronym of Groningen Image Processing SYstem. It is a highly interactive software
system for the reduction and display of astronomical data. It was designed originally for the
reduction of interferometric data from the Westerbork Synthesys Radio Telescope, but over the
last 20 years it has grown to a system capable of handling data from many different instruments
(e.g. TAURUS, IRAS etc.).
This guide is intended for astronomers who want to use GIPSY for the reduction of their data.
Part I deals mainly with the use of GIPSY. This part is split up in several chapters. Chapter 2
explains how to get started with GIPSY. The subsequent chapters deal with general utilities
within GIPSY (chapter 5), and instrument specific reduction programs e.g. radio (chapter 6) or
IRAS (chapter 7). The last chapter (chapter 8) of part I deals with the more advanced features of
GIPSY such as batch processing, the use of COLA files and even developing your own programs
in GIPSY.
Part II deals in much more detail with the basic design and architecture of the GIPSY system.
It is intended more as backround reading material for the interested astronomer. In principle
part II need not be read to be able to use GIPSY, however it may well help you in speeding up
your reduction if you understand the inner structure of GIPSY.
The appendices contain specific system information dealing with e.g. the hardware requirements
for running GIPSY, and local definitions.
1

2 Chapter 1.
Conventions
This guide uses the following conventions on notation and terminology.
ffl Within a command line, uppercase letters and words in the typewriter font represent
computer output. For example, in the command line
INSET=AURORA
the keyword INSET= is typed by the computer.
ffl Within a command line, letters and words in the sans serif font represent user input. Thus
in the example above the user entered AURORA. Input is case sensitive.
ffl Outside command lines, the typewriter font is used for keywords (see section 9.9) and
descriptor items (see section 9.7). Keywords have the equals sign as last character. For
example, DATAMAX indicates a descriptor item and BOX= a keyword.
ffl Outside command lines, the font sans serif indicates program names, for example, DISK.
ffl In astronomy, the terms image and map often are interchangeable. This guide follows the
convention to use the term image rather than map. Where replacement is not possible,
you will still find the term map.

Part I
Using GIPSY
3


Chapter 2
Getting started
2.1 Introduction
In this chapter the basic commands needed to run a GIPSY session are described. It is by no
means intended to be complete, however it should suffice to get you started. It is intended as a
quick­start manual. The first section describes the preparation you need to do before using to
use any GIPSY software. Section 2.3 gives all the basic commands for a GIPSY session: startup,
running tasks, stopping etc. The next section (section 2.4) explains the use of GIPSY data sets,
and the last section describes a real­live GIPSY session as an example.
For all site­specific information you should contact the local system manager.
2.2 Preparation
If you are lucky, somebody will have prepared a proper environment for you, and you can skip
this section. If not, you'll have to prepare some things to run GIPSY.
Obviously first you will have to find a computer on which you are allowed to log onto. On this
computer you should have at least several tens of Megabytes of disk space for your data files
and log files (a typical 512 by 512 pixel image will occupy ¸1 Mb of disk space).
If you want to use tape drives, acquaint yourself with their location and (logical) names. If you
are going to use a workstation you may want to find some background material on using the
X­window environment (see also sections 9.3 and 9.6).
To be able to run GIPSY you may have to setup a GIPSY environment on the computer you are
going to work on. Setting up such an environment is described in the document gipsy local.dc0
(ask your local system manager).
2.3 The basic commands
To have a GIPSY session proceed as follows:
1. Log in on the computer
5

6 Chapter 2.
This is somewhat system dependent, but usually you need a user name and password.
Enter it on the prompt, and you're in business.
On workstations you must set up the X­window environment. This is sometimes done
automatically, on most systems you must give a command yourself, ask your local system
manager how to do this.
Then go to the subdirectory where you want to have your data files etc. (on unix type e.g.:
cd work to go to your own subdirectory work).
2. Starting a GIPSY session
To start the session (on a VT­100 terminal or window) type gipsy !CR?. 1
This will set up the environment as needed for GIPSY and start the master control task
HERMES (refchapter:hermes). HERMES is the master program which will check all your
inputs before they get passed on to the operating system or to individual tasks. You really
do need it!
HERMES will set up a screen divided into three parts (see figure 2.1).
ffl The top part of the screen contains the Common Output Area (COA). In this area
a part of the log file, where all tasks put their results, is shown. You can skip back
and forth through this log file using the !tab? and !line feed? keys. The page
indicators in the Task Status Area show you which page of the log file is displayed
and the page number of the last page of the log file.
ffl The middle part of the screen is the Task Status Area (TSA). Here status messages
of tasks are shown. Programs that require parameters will inform you of this in the
TSA.
ffl The bottom part of the screen is the User Command Area (UCA). Everything typed
by the user ends up on these two lines (they function as one long line). Thus all
commands go through here. Also tasks, when requiring input, will prompt with a
keyword in the UCA.
3. Starting a task
To start a task (also called an application), its name must be entered in the UCA followed
by !CR?(e.g. DISK!CR? to start disk). The program will then start (indicated by the
status ''WAITING TO BE RUN'', followed by ''RUNNING'' in the TSA), and subsequently
prompt the user for input using keywords.
4. Supplying a task with parameters
Giving a task parameters is done through keywords. They are asked by a task when the task
needs information. A keyword is a character string followed by an equals sign, e.g. INSET=
Following the equals sign values can be given. Depending on the function of the keyword
1 Under X­windows you can try xgipsy !CR?to start a session using the X­window version of HERMES. Use
this option with some caution, XHermes is still under developement.

Getting started. 7
\Gamma \Gamma
Common Output Area
OUTPUT FROM TASKS
\Gamma \Gamma Task Status Area
clock
last logfile page
@ @ current logfile page
\Gamma \Gamma User Command Area
DISK INSET=AURORA
­
­
­ DISK Give set to examine [stop]
­ VIEW Displaying set AURORA FREQ 1
39 103
15:35
@
@ @ text typed by user
@
@
@ @ keyword prompt from task
@
@
@
@
@ task requesting parameter(s)
@ @ explanation for keyword
\Gamma \Gamma status message of task
Figure 2.1: The layout of the GIPSY screen as setup by HERMES
values can be floating point numbers, integers, character strings and even expressions. If
input given by the user is not as requested by a program (e.g. the program asks for an
integer and the user enters text), the keyword will bounce, and you will be prompted
again with the same keyword. All keywords asked by a task are listed and explained in the
documentation of that task. When a keyword is asked by a program, a one­line message
will appear in the TSA.
Many keywords have defaults; the value that is used when the user presses !CR?without
a value. If a keyword has a default, the default value is given between square brackets in
the TSA message.
Besides waiting for a task to prompt you with keywords there are two other ways to specify
them. Firstly, when starting up a task you can pre­specify keywords on the same command
line (e.g. DISK INSET=AURORA!CR? to start disk for set AURORA). Secondly, when
a task is running you can also set a keyword by typing taskname keyword=value. When a
keyword is pre­specified like this, it will not be asked anymore.
Hidden keywords are keywords which are never prompted, and which always have a sensible
default value. You can change their value by pre­specifying them when starting up a task,

8 Chapter 2.
or by specifying them together with the taskname. Hidden keywords should be considered
as fine­tuning parameters; for many general applications you do not need to use them.
5. Aborting a task
Any task can be aborted by typing its name in the UCA and then typing !Ctrl?C. If
there is only one task running, you need not type its name, !Ctrl?C will kill it.
6. Getting help
When under HERMES you can always get help by typing !Ctrl?H.
If there is a task name with a keyword in the UCA, the help will be the part of the task
documentation relevant for that keyword. If there is only a task name in the UCA, you
will get the first page of the task documentation. And if there is nothing in the UCA, you
will get help on HERMES.
You can browse through the documentations using the !tab? and !line feed? (or
!Ctrl?I and !Ctrl?J) keys. By typing !Ctrl?H again you will go back to your session.
7. Ending a GIPSY session
HERMES can be stopped by typing !Ctrl?Q, you are then asked if you to confirm that
you really want to stop. You are then returned to at system level.
8. Keeping track of things
GIPSY keeps a log file. An ASCII version of this log file (named GIPSY.LOG) will be
present in the working subdirectory after the session. You can print this file with any
standard printing command.
2.4 GIPSY data sets
Data in GIPSY are stored in so called sets. These are n­dimensional arrays of floating point
numbers together with a header describing the data. Every axis of a data set has a name, a
length in pixels and physical coordinate system associated with it (all specified in the header).
Elements of the data set can be identified using an n­dimensional grid coordinate. The user gives
such a set whatever name he likes.
A typical radio dataset might be a 3­D ''cube'' named AURORA, with axes RA, DEC and
FREQ. Pixel, or grid, coordinates in such a set can be seen as triplets; (RA,DEC,FREQ).
2.4.1 Sets and subsets
Within sets there are so called subsets. These parts of the n­dimensional set for which one or more
of the coordinates are fixed. For example an RA­DEC plane at FREQ grid 32 is a 2­D subset of
the cube AURORA above. And, in the most extreme case, the pixel at say (RA,DEC,FREQ) =
(2,34,11) is a 0­D subset of AURORA.
When programs ask for an input set, they usually allow you to specify a subset of the data.
Specifying one or more subsets is done by specifing the axis name(s) and grids you want for

Getting started. 9
Input string function
\Lambda hh mm ss Right Ascention hh mm ss for epoch of set
\Lambda dd mm ss Declination dd mm ss for epoch of set
\Lambda1950 hh mm ss Right Ascention hh mm ss for epoch 1950
.....
See chapter 3
Table 2.1: Some GIPSY position input formats
each subset. E.g. SET=AURORA FREQ 3, specifies the subset FREQ=3 (i.e. the RA­DEC
plane at FREQ grid 3) of the set AURORA. Similarly AURORA FREQ 1 2 3 4 8 (or shorthand
AURORA FREQ 1:4 8) specifies 5 subsets: 5 RA­DEC planes in AURORA. Specifying only
the axis name, and no grids, selects all subsets along that axis (AURORA FREQ selects all
RA­DEC planes in AURORA). Again you could specify INSET=AURORA RA DEC FREQ....
guess what happens.
For more details on sets and subsets see chapter 3.
2.4.2 Specifying a position in a (sub)set
Many programs will ask for a position in a (sub)set. This is usually done using the keyword
POS=. When this keyword is asked programs will tell you what coordinates you must specify and
in what ranges (in pixels) you can specify them.
For this keyword you can then enter a grid position. Also you can enter some number corre­
sponding to the physical units along that axis if you postfix that number with the units in which
it is. For example in the AURORA FREQ 10 subset you will need to specify RA and DEC for
POS=. This could be POS=3 5(in grids) or POS=* 14 26 9 * ­12 3 5.4.
For an n­dimensional subsets you will have to specify an n­tuple coordinate; e.g. POS=3 5 10
specifies the same grid point as above but now starting from the full set AURORA.
Chapter 3 lists all available input formats, pre­ and postfixes.
2.4.3 Specifying an area
In many programs you want operations to be performed on specified areas of (sub)sets. More
general, operations need to be performed on an n­dimensional section of an m­dimensional set
(nŸm). Such a section is called a frame (for more details on frames see section 9.7).
Programs will prompt for a frame usually using the keyword BOX=. Similar to the POS= keyword,
the programs will inform the user of which ranges in which coordinates can be specified. Note
that in this definition of frame, it need not be 2­dimensional. To specify the frame yow nou have
to give two positions one for the lower left, and one for the upper right corner of the frame.
For entering these positions the same formats can be used as for the POS= keyword (see also
Table 2.4.2.

10 Chapter 2.
2.5 A sample GIPSY session
At the unix prompt type: gipsy Wait until HERMES is installed. Now you can start GIPSY
applications. In this sample GIPSY session, the progams DISK, STAT, and VIEW were used.
The results displayed in the log file are:
!USER? disk
***DISK***
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
nr SETNAME descr image Axis name(s) and size(s)
(kb) (kb)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
1 cg1517 48 10240 (RA,DEC,VEL) = (256,256,40)
2 n6946 48 (RA,DEC,DEC) = (512,512,63)
3 rosimfb1 48 225 (RA,DEC) = (240,240)
4 total 48 1024 (RA,DEC) = (512,512)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
Descriptors: 192 kb
Images : 11489 kb
Directory : 13072 kb
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
!USER? DISK INSET=
!STATUS? DISK +++ FINISHED +++
!USER? stat
!USER? STAT INSET=rosimfb1
Set rosimfb1 has 2 axes
RA­­­TAN from ­119 to 120
DEC­­TAN from ­119 to 120
!USER? STAT BOX01=
BOX range for set rosimfb1 :
RA­­­TAN from ­119 to 120
DEC­­TAN from ­119 to 120
subnr pixels sum mean rms min max blanks
=============================================================================
1 57447 3.01 5.245E­05 .263 ­.628 1.67 153
=============================================================================
!STATUS? STAT +++ FINISHED +++
!USER? view box=­20 ­20 20 20
!USER? VIEW INSET=rosimfb1
Set rosimfb1 has 2 axes

Getting started. 11
RA­­­TAN from ­119 to 120
DEC­­TAN from ­119 to 120
BOX range for set rosimfb1 :
RA­­­TAN from ­20 to 20
DEC­­TAN from ­20 to 20
!USER? VIEW CLIP=
!STATUS? VIEW +++ FINISHED +++
The application DISK displays the GIPSY sets that are on disk. The second file in the table
has a descriptor part but not an image part. Displayed are the total amount in kilobytes of all
descriptors, all images and all files in the current directory. STAT gives an impression of the
properties of the data. VIEW displays part of the image. The size of the box is prespecified.
VIEW opens a new window where GIDS ( Groningen Image Display Server ) is started. With
your mouse you can click several buttons to start actions like zooming, scaling etc.
2.6 Bug handling in Gipsy
To structure the registration of bugs in GIPSY applications, the program BUG is written. A
bug is associated with a subject, which is usually the name of the application. It is possible that
you want to report a bug that is already reported by somebody else. To avoid this situation,
use the keyword SUBJECT= to obtain a list with reported bugs. If you select a subject, you can
read all the reports about this subject by giving the report number to REPORT=. The keyword is
asked in a loop. If you want to continue, press carriage return. With keyword SUMMARY= a short
description of the bug must be given. The text containing the complaint or description of the
bug, can be given interactively or from an input ASCII file. Pressing ! CR ? at the INPUT=
prompt will put you in the interactive mode. Your report will be send to the mailbox of the
Gipsy manager (i.e. user ''Gipsy''). The program BUG is also used by programmers to mail you
back if your bug is fixed.
2.7 News
Latest news concerning GIPSY is found with the application NEWS. By default it will display
only the news that you did not read before, but MODE=ALL displays all news items, including
old ones. A selection on items can be made with MODE=SELECT which will prompt the user with
ITEMS=.

Chapter 3
Input syntax
3.1 Introduction
Giving a task parameters is done through keywords. Keywords are asked by a task when the
task needs information. A keyword is a case­insensitive character string followed by an equals
sign (f.i. INSET=). Following the equals sign, values can be given. Depending on the function
of the keyword these values can be floating point numbers, integers, character strings and even
expressions. Context­sensitive help about keywords is provided at a single keystroke !Ctrl?Q,
(or button­press when working in xHermes). Parameters for a task can be specified in the
command that starts the task and thereafter at any moment while the task is active. A task
requiring input from the user causes Hermes to find out whether it has already been specified
and if not, prompt the user. Before a parameter value is passed to a task, Hermes first checks
whether it meets the task's request and if not, Hermes rejects that value and prompts again.
3.2 Input of structures and substructures
A set is an n­dimensional data structure with n different axis names. The contents of the set
are floating point numbers stored in a file with the extension ''image''. The description of the
structure is stored in a file with extension ''descr''. Substructures (subsets) have dimensions in
the range 0..n. A subset of dimension 0 is a pixel and a subset of dimension n is the whole data
set. If the dimension is less than n, there are multiple subsets possible in a set. This number
depends on the number of axes (and their sizes in pixels) that are not part of the subset. The
structure is specified by a character string i.e. the name of the set (less than 80 characters
including a path) and the subsets by the name of one or more axes outside the subset and
numbers indicating pixel positions along those axes. In short, the following format applies:
! structure ?! sub:axis1 ?! lo ?:! hi ?! sub:axis2 ?! lo ?:! hi ? :::
The substructure axes can be found under the header item CTYPEi where i=1..n. CTYPE's can
be displayed with f.i. the program FIXHED (run: FIXHED ITEM=HEAD ).
12

Input syntax. 13
CTYPE Meaning
RA Equatorial, right ascension
DEC Equatorial, declination
GLON Galactic longitude
GLAT Galactic latitude
ELON Ecliptic longitude
ELAT Ecliptic latitude
SLON Supergalactic longitude
SLAT Supergalactic latitude
FREQ Frequency
VELO Velocity axis
LAMBDA Wavelength
INVLAM Inverse Wavelength
LOGLAM Log(wavelength)
TIME Time
POLN Polarisation
PARAM Parameter axis
SAMPL IRDS sample axis
TICK IRDS tick axis
SDET IRDS detector axis
SNIP IRDS snip axis
Table 3.1: Possible GIPSY axis names

14 Chapter 3.
Axis names from table 3.2 can be abbreviated because minimum matching is used. By default
the last axis is used and lo and hi indicate pixel positions along the axis following the integer
input rules. If an axis name is given but not a number, all subsets along that axis will be
generated. Usually sets are asked by the keyword INSET= (or variants).
ffl Examples: the structure AURORA is 3­d and has axes RA,DEC and FREQ with sizes:
RA from ­63 to 64
DEC from ­63 to 64
FREQ from 1 to 32
INSET=AURORA FREQ 10:18 24
INSET=AURORA F 10:18 24
INSET=AURORA 10:18 24
give 2­d planes (RA,DEC) for values of FREQ 10 to 18 and 24.
Following the integer input rules (section 3.3), you are
also allowed to give weird expressions like:
INSET=AURORA F 11:2:\Gamma1 12
which generates 2­d planes (RA,DEC) for values of FREQ 11 to 2 and 12
INSET=AURORA F
INSET=AURORA 1:32
give 2­d planes (RA,DEC) for values of FREQ 1 to 32
INSET=AURORA DEC 5:10 FREQ 10
gives 1­d lines (RA) for values of DEC 5 to 10 at FREQ 10
INSET=AURORA
gives the whole 3­d cube
INSET=AURORA DEC 1
gives 2­d plane (RA,FREQ) for a value of DEC 1
INSET=AURORA RA 0 DEC 0 FREQ 1
gives a pixel at (RA, DEC, FREQ) = (0, 0, 1)
Most applications repeat their operations for the specified axes (class 1 programs). Therefore you
could call these axes 'repeat' axes. Some applications (class 2) however (f.i. MOMENTS, GAUFIT,
MEAN, SUM) need the specification of a so called 'operation' axis. For example MOMENTS
requests one operation axis, this is the integration direction. The operation is carried out but
not repeated in this direction.

Input syntax. 15
ffl Examples:
MOMENTS INSET=AURORA FREQ 2:20 BOX=­63 ­63 64 64
gives a velocity field of the set AURORA for all RA and DEC.
MEAN INSET=AURORA F BOX=­63 ­63 64 64
gives for all pixels in the RA­DEC plane the average over all frequencies.
MEAN INSET=AURORA RA ­10:10 DEC ­10:10 BOX=1 32
gives an average spectrum (averaged over RA from ­10 to 10 and DEC from ­10 to 10) for
frequencies 1 to 32.
The documentation should state whether class 1 input or class 2 input is necessary. Also the
structure of your output is explained in the application documentation.
3.3 Input of floating point or integer numbers
Floating point or integers numbers can be typed as numbers and/or expressions.The num­
bers/expressions can be typed on one line, separated by blanks and/or a comma. There is a
loop­facility implemented, which has the format s:e[:i], where s = start value, e = end value and
i = increment value (default: 1), and a repeat­facility, which has the format v::n, where v =
value to be repeated and n the repeat­count of v. There is also a list­facility, which is a string
of numbers/expressions enclosed between [square brackets]. A list is treated in expressions as a
kind of array. The expression is evaluated for each list element (from left to right) separately.
Loops, repeats and lists cannot be nested!
ffl Examples:
1 2 3/3 sin(pi) yields 1.0 2.0 1.0 0.0
log(10)::4 yields 1.0 1.0 1.0 1.0
log(10):log(100):2/4 yields 1.0 1.5 2.0
10**[0 1 5] yields 1 10 100000
10**[0:3] yields 1 10 100 1000
Suppose an inclination at keyword INCL= must be given in degrees, but you want the
input in axis ratio.
INCL=DEG(ACOS([0.3 0.5]))

16 Chapter 3.
Between square brackets (the list facility) are the arguments 0.3 and 0.5. The expression
evaluates the two values for the ACOS and converts these values to degrees. The result is
that the values 0.3 and 0.5 are converted to the angles 72.5424 and 60.0 deg.
In numerical expressions the following operators are available:
+ addition
­ subtraction
* multiplication
/ division
** power
The following predefined constants are available:
PI ú (3.14159....)
C speed of light (SI)
H Planck (SI)
K Boltzmann (SI)
G gravitation (SI)
S Stefan­Boltzmann (SI)
M mass of sun (SI)
P parsec (SI)
BLANK universal undefined value
The following functions can be used:
abs(x) absolute value of x
sqrt(x) square root of x
sin(x) sine of x
asin(x) inverse sine of x
cos(x) cosine of x
acos(x) inverse cosine of x
tan(x) tangent of x
atan(x) inverse tan of x
atan2(x,y) inverse tan (mod 2ú)
x = sin, y = cos
exp(x) exponential of x
ln(x) natural log of x
log(x) log (base 10) of x
sinh(x) hyperbolic sine of x
cosh(x) hyperbolic cosine of x
tanh(x) hyperbolic tangent of x
rad(x) convert x to radians
deg(x) convert x to degrees
erf(x) error function of x
erfc(x) 1­error function
max(x,y) maximum of x and y
min(x,y) minimum of x and y
sinc(x) sin(x)/x (sinc function)
sign(x) sign of x (­1,0,1)
mod(x,y) gives remainder of x/y
int(x) truncates to integer
nint(x) nearest integer
ranu(x,y) generates uniform noise between
x and y
rang(x,y) generates gaussian noise with
mean x and dispersion y
ranp(x) generates poisson noise with mean x
ifeq(x,y,a,b) returns a if x = y, else b
ifne(x,y,a,b) returns a if x 6= y, else b
ifgt(x,y,a,b) returns a if x ? y, else b
ifge(x,y,a,b) returns a if x – y, else b
iflt(x,y,a,b) returns a if x ! y, else b
ifle(x,y,a,b) returns a if x Ÿ y, else b
ifblank(x,a,b) returns a if x = BLANK, else b
3.4 Input of logicals
Logicals are decoded in the following way: YES, JA and TRUE result in a logical which is true,
NO, NEE and FALSE give a logical which is false. It is sufficient to give the first letter of the
possible affirmative and negative replies. Any other answer will result in a syntax error.

Input syntax. 17
ffl Examples:
PLOTGRIDS=N
OK=YES
3.5 Input of character strings
Normally character strings are case­sensitive, but individual tasks can deviate from this or
convert to either uppercase or lowercase. Some programs can pass an array of characters. The
characters are then separated by blanks and/or comma's. Sometimes spaces however can be part
of the string. The input is called text then and carriage return closes the text.
ffl Examples:
INSTRUME=WSRT (character string)
COMMENT=Set smoothed on 2­2­92 (text)
3.6 Input of coordinates
You can specify the sizes of the substructures, i.e. the sizes of the subset axes. Usually you are
asked to do so with the keyword BOX=. Positions can be entered either as pixel positions or as
physical coordinates (provided that the relevant header items are correct).
To define a box, there are two general input possibilities:
! lower position ?! upper position ?
! lower position ? and ! upper position ? indicate the lower­ and upper corner of the
substructure and have the same dimension as the subset.
! centre position ? D ! size ?
with ! size ? indicating the rectangular size of a box centered on ! centreposition ?. The D
stands for Delta. If only the size is given, the box input routine will prompt you to specify the
central position in CPOS=
The general format for a position in an n­dimensional subset is (prompted with POS= or POSITION=):
! n \Gamma tuple value ?
There are two symbols that denote one position. The first one is PC. This stands for Projection
Centre and is effectively grid (0,0,...). The second is AC which means Axis Centre. If the length
of axis i is NAXISi and the reference pixel is pixel number CRPIXi then the i­th coordinate of AC
is given by the expression NAXISi=2 \Gamma CRPIXi. In most cases this will be [(hi+lo+1)/2, ...]. If the
specification for BOX= is a size only, the application will prompt the user with CPOS= complete
the input.

18 Chapter 3.
ffl Examples:
STAT INSET=AURORA DEC 0 BOX=­30 1 20 32
gives a RA­FREQ plane with RA from ­30 to 20 and FREQ from 1 to 32
STAT INSET=AURORA F 1 BOX=0 0 D 7 6
is a RA­DEC plane with RA from ­3 to 3 and dec from ­2 to 3 (Central position is 0,0,
size of the box is 7x6).
STAT INSET=AURORA F 1 BOX=PC D 10 10
results in a RA­DEC plane with sizes 10x10 centered around the projection centre.
COORDS INSET=AURORA F 1 POS=PC
determines the physical coordinates of the projection centre in set AURORA.
If the correct header items and the correct axes names are entered, you can replace the grid
coordinates with physical coordinates. If a coordinate is not followed by a unit, it is assumed to
be a grid otherwise it will be converted. A position on a FREQ axis might be given then as:
POS=32 just a grid
POS=1418.6 MHZ a frequency
POS=300000 M/S a velocity
If you want to enter physical coordinates in the units corresponding to the axis units, it is possible
to prefix the values with 'U'. If the axis has secondary units, these units are used instead of
the primary units. For example if CTYPE3 is 'FREQ' (primary units MHZ) and DTYPE3 is 'VEL'
(secondary units M/S), than:
POS=U 300000 is equivalent to POS=300000 M/S
For spatial axes there are a number of prefixes:
ffl Examples:
POS=\Lambda 10 12 8 \Lambda ­67 8 9.6
RA = 10 hour, 12 min, 8 sec, DEC = ­67 deg, 8 min, 9.6 sec., in a 2­d area and in the
epoch as found in the header of the set.

Input syntax. 19
DEGREE ARCSEC ARCMIN RADIAN
CIRCLE METER ANGSTROM MICRON
MM CM INCH FOOT
YARD M KM MILE
PC KPC MPC TICK
SECOND MINUTE HOUR DAY
YEAR HZ KHZ MHZ
GHZ M/S MM/S CM/S
KM/S K MK JY
MJY TAU
Table 3.2: Units recognized by GIPSY
Input string function
\Lambda for RA or DEC in resp. HMS and DMS in EPOCH of set.
\Lambda1950 for RA or DEC in resp. HMS and DMS in EPOCH 1950.0
\Lambdaxxxx.x for RA or DEC in resp. HMS and DMS in EPOCH xxxx.x
G Galactic longitude or latitude in degrees
E Ecliptic longitude or latitude in degrees
S Supergalactic longitude or latitude in degrees
Table 3.3: Possible GIPSY position input formats

20 Chapter 3.
POS=\Lambda2000.0 3 14 38.02 \Lambda2000.0 41 13 54.84
Input of RA 3 h 14 m 38.02 s, DEC 41 d 13 m 54.84 s in epoch 2000.0
BOX=G 56.7 G 9.89 D 12 ARCSEC 10 ARCSEC
Input of a box centered at 56.7 degrees galactic longitude and 9.89 degrees latitude with
size 12x10 seconds of arc.
Some applications use conversion routines independent of the set header, for example to convert
angles given in HMS or DMS to a real value. The documentation (for example: userangle.dc2)
will explain the input syntax. Also some applications use a special input routine based on the
input routines for reals. This routine allows input of the values ­INF and INF (typed as ­inf and
inf) as minimum and maximum of the image. You can expect to be able to use these values if
you encounter the RANGE= keyword. Again, the application will contain documentation about
this.

Chapter 4
Hermes
This chapter describes Hermes, the user interface of the Groningen Image Processing SYstem
(GIPSY). It is meant as both an introduction for new users and a reference document for more
experienced users.
4.1 What is Hermes?
Hermes is the user interface of GIPSY. It enables users to do multi­tasking in an organised
fashion. Users have direct control over the application programs (tasks) they run: a running
task can be suspended or aborted with a simple command; various settings can be changed
while a task is running.
Parameters for a task can be specified at any time; if a task needs information that has not been
specified yet, the user is prompted.
Context­sensitive help about tasks is provided at a single keystroke or button­press.
Tasks keep the user informed in two ways: they write in a log file in which the user can page
and search and they can provide a one­line status message, which can be frequently updated.
At the moment of this writing three versions of Hermes exist:
ffl tHermes, which runs on standard character display terminals. this is currently the standard
version for interactive work.
ffl xHermes, an experimental version based on the X Window system. This version is in a
number of respects incompatible with other versions of Hermes.
ffl nHermes, a non­interactive version intended for batch work.
Normally Hermes is not started directly by the user, but rather by a shell script which prepares
a number of settings before starting Hermes. Refer to the GIPSY users guide.
4.2 Tasks
Tasks in GIPSY are the application programs which do useful work for the user. They consist
of one or more processes (usually one) which communicate with the user through a formalized
21

22 Chapter 4.
collection of interface routines. Because of the use of these interface routines, tasks can be run
from any version of Hermes.
Though tasks can be run from all versions of Hermes, not all tasks can be run successfully
from all versions because a version of Hermes might not implement all interface functions.
xHermes is currently the only version which does not implement all functions: it does not
support the DEPUTY function which is used by tasks to start another task. The most important
consequence of this is that the task COLA cannot be used under xHermes.
COLA­scripts can be started as tasks. For information about the use of COLA refer to the
document cola.dc1 and chapter 8.4)
4.3 User input
4.3.1 Introduction
Parameters for a task are passed to it via keywords. A keyword is a character string followed by
an equals sign, e.g. INSET=. Keyword names are case­insensitive. Parameters for a task can be
specified in the command that starts the task and thereafter at any moment while the task is
active. A task requiring input from the user causes Hermes to find out whether it has already
been specified and if not, prompt the user. Before a parameter value is passed to a task, Hermes
first checks whether it meets the task's request and if not, Hermes rejects that value and prompts
again.
As the execution of the task proceeds, Hermes builds up a table of the task's keywords and
associated values. At task termination this table is saved in order to allow the user to run the
task again with (partly) the same parameters.
Three classes of keywords are recognized:
1. Forced , which are keywords for which no task default is allowed. The user must respond
to the prompt with a correct value.
2. Defaulted , which are keywords which have a default value defined by the task. If the
keyword has not already been specified then the user will be prompted. If on this occasion
the user types only a !RETURN?, this signifies that the task default is acceptable and should
be used. Any other input will override the default.
3. Hidden, which are keywords for which the user is never prompted and which have a default
value defined by the task. They can be specified by unprompted input by the user. The
documentation of a task must be read to find out if it uses hidden keywords.
The user can set a parameter in the task context to change requests for hidden keywords
into requests for defaulted keywords. (``Unhide'' hidden keywords: CTRL­S)
Hidden keywords are sometimes used to control looping in a task. Each cycle round the
loop, the task requests the value of a hidden keyword. If it has not been specified, the
task takes the default and looping continues. If the user defines the keyword then that
value is sent to the task which could cause the task to terminate the loop.

Hermes. 23
4.3.2 Parameter syntax
Basically Hermes is capable of providing tasks with the following types of parameters: integer
numbers, real numbers, double precision reals, logicals and character strings. Tasks may however
request input in the form of character strings and perform their own decoding to obtain numerical
information. One parameter value can contain one or more elements.
Normally character strings are case­sensitive, but individual tasks can deviate from this or
convert to either uppercase or lowercase.
In the case of integer or real numbers, the characters typed are converted to the required type.
The Fortran syntax for numbers applies. It is also possible to supply an expression, includ­
ing function references and predefined constants. Lists of numbers can be specified using the
`start:end:increment' notation, where the `:increment' part is optional and defaults to one.
In the following example a list of 8 elements is specified:
CONT= ­1.5:2:0.5
For logicals the inputs YES, JA or TRUE are affirmative (the first letter is sufficient). Other inputs
result in NO.
If a task requests a keyword repeatedly, the user can pre­specify inputs in two ways. The
first method is separating the inputs with semicolons, e.g.
POS= 10 20; 15 25; 30 30
Please note that a trailing semicolon designates an empty input for which a default is to be
taken. The second method consists of specifying a file (``recall file'') as input to the keyword.
This must be a text file with a name like ``name.rcl''. Every line in this file is a separate
input. Either the whole file or a part of it can be specified:
!name use the whole file;
!name n:m use line numbers n to m;
!name :n use line numbers 1 to n;
!name n: use line numbers n to the end of the file.
It is possible to specify a recall file in a semicolon­separated list, but within a recall file
semicolons cannot be used. Recall files cannot be used recursively, i.e. a recall file can not
contain a reference to another recall file.
When the task has ``consumed'' all pre­specified input on a keyword, the next request for that
keyword will cause the user to be prompted in the normal way. Inputs given on repeatedly
requested keywords are stored in a semicolon­separated list, so if a task is re­run with the
previous set of parameters, all inputs are available again.
If unprompted input is given on a keyword of which all pre­specified input has not been
consumed yet, the new input will supersede the complete previous set of inputs.
Keywords can be prespecified in a text file with a name like ``name.def''. This (``default file'')
can contain any number of keywords=values combinations including the use of recall files. User
supplied parameters are higher in the parameter hierarchy than the parameters specified in a
default file. In tHermes the syntax to use a default file is:
! name of default f ile without extension ?! (program name) ?
example: if myplot.def is a default file for CPLOT start with: MYPLOT(CPLOT)

24 Chapter 4.
4.3.3 Numerical input
In numerical expressions operators, constants and functions can be used (See chapter 3)
4.4 Task context
Tasks all run in a context . This context consists of a number of user­settable parameters:
ffl Error level. If a task generates an error at or above the current error level, Hermes will
abort the task.
ffl Message level. If a task generates an error at or above the current error level, Hermes
will display the associated error message.
ffl Output mode. This parameter determines whether test messages from tasks will be
displayed and whether messages unnecessary for experienced users will be suppressed.
ffl Device status. Two parameters indicating whether messages sent to either the screen
or the log file actually be written.
ffl Hide status. This parameter determines whether ``hidden'' user input requests from the
task will cause the user to be prompted anyway.
ffl Finally there are four parameters which determine what kind of status messages will
be logged.
Tasks normally inherit their context from a template context. If a task is started by another
task, it inherits the context of that task. Both the template context and the context of any
running task can be changed by the user. The way in which this can be done depends on the
specific implementation of Hermes. When Hermes is started, the template context contains
sensible defaults.
4.5 tHermes
4.5.1 Introduction
tHermes is the version of Hermes which communicates with the user through standard character
display terminals, including X11 terminal windows. It organises the terminal screen in a special
window­like way. The most important permanent components (windows) of the screen lay­out
are:
ffl User Command Area (UCA). This occupies the lower two lines of the terminal screen and
is the focus of user­to­task communication.
ffl Task Status Area (TSA). This consists of four lines above the UCA which can each contain
information reflecting the current status of a task.
ffl Common Output Area (COA), the remaining top part of the screen which shows a part
of the log file. Here user commands are logged and tasks can write text.

Hermes. 25
Other permanent components are a clock display and numbers which indicate which part of the
log file is mapped to the COA.
Components of the screen lay­out which are not permanent are called transient windows. These
overlay the permanent screen components or other transient windows. For example the context­
sensitive help display overlays (part of) the Common Output Area. Examples of transient win­
dows are the already mentioned help display, a menu window allowing the user to change specific
task settings, prompter windows in which for instance a search string can be specified, a Unix
shell window, etc.
Many functions of tHermes can be invoked by typing a control key (designated as CTRL­c, where
c is a letter), or by typing an escape sequence (the ESC character followed by an other character).
Important control keys are: CTRL­Q to quit from Hermes, CTRL­C to abort a task or to break
out of a transient window, CTRL­O to switch the ``keyboard focus'' between terminal windows
waiting for keyboard input, and CTRL­L to repair a damaged screen lay­out.
4.5.2 User Command Area
The User Command Area (UCA) consists of the bottom two lines of the terminal screen where
most interaction with the tasks takes place. The user can type task­related commands in the
UCA and Hermes can put there task­related prompts. An important aspect of the prompts is
that they are treated in exactly the same way as information typed by the user, i.e. the user can
erase or modify a prompt supplied by Hermes as if he typed it himself. Prompts in the UCA are
always in the form of a legal complete or partial command.
The information in the UCA is used as the context for a number of functions of Hermes. E.g.
CTRL­H causes the user document of any taskname present in the UCA to be displayed and
CTRL­C aborts the task if it is active.
The two lines of the UCA are one logical long line which can be edited using the following control
keys of which most are EMACS­compatible.
CTRL­A move to start of line
CTRL­B move one position back
CTRL­D forward delete one character
CTRL­E move to end of line
CTRL­F move one position forward
CTRL­K forward delete rest of line
CTRL­T replace complete line with next active task name (see below)
CTRL­U delete complete line
DEL backward delete one character
space replace complete line with next prompt for user input (see below)
Characters CTRL­T and space are somewhat special. CTRL­T erases the UCA and then
prompts with the name of an active task. It does this in a circular fashion so if more than
one task is active, another taskname is displayed when CTRL­T is pressed again.
If the UCA is ``free'' (a subtle concept explained below), pressing the space bar does a similar
thing for tasks waiting for input. This makes it easier for the user to do something else before
he supplies the requested input, e.g. run another task which supplies information that helps
to give the input.

26 Chapter 4.
The UCA is ``free'' when it is empty, or when it only contains an unmodified prompt supplied
by Hermes.
4.5.3 Task Status Area
The Task Status Area (TSA) is the middle section of the terminal screen. It consists of four
lines which each can contain status information of an active task. The format of a task status
entry is one of the following:
ffl When a task has been activated, but is not running yet:
taskname WAITING TO BE RUN
ffl When a task is running:
taskname RUNNING
or
taskname status message supplied by servant task
ffl When a task is prompting for user input:
taskname prompt message supplied by servant task
ffl When a task is suspended:
taskname PAUSING
or
taskname PAUSING message supplied by servant task
ffl When a task is waiting for another task to finish:
taskname WAITING FOR other taskname
ffl When a task has finished processing normally:
taskname +++ FINISHED +++
ffl When a task has been aborted by the user:
taskname USER ABORT
ffl When a task has encountered an error fatal to execution:
taskname error message ­FATAL
ffl When a task has crashed (i.e. exited without notification to Hermes):
taskname CRASHED
4.5.4 Common Output Area and Log File
The Common Output Area (COA) on the terminal screen is the remaining top area of the
terminal screen not used for the UCA or TSA. It is a viewport on the log file. Hermes treats
the log file as a ``book'' with numbered pages. Normally Hermes shows the current page of the
book, that is the page on which output is currently being written.
The COA has two modes of operation: page mode and non­page mode. In non­page mode the
page on the screen is always the current page. If necessary, Hermes will flip the page. The

Hermes. 27
current page number is displayed at the extreme right of the Task Status Area. In page mode
the information on the screen will stay there until the user instructs Hermes to change the page.
Though the user does not see it, output can still be written to the log file. In page mode the
number of the displayed page is shown to the left of the current page number. Page mode can
be switched on and off by pressing CTRL­P.
The log file can be traversed in backwards direction by pressing the CTRL­Z key (or on ANSI
keyboards the PageUP key). Paging forward is done with the CTRL­N key (or ANSI PageDown).
Text search in the log file is done by pressing CTRL­R (reverse) or CTRL­S (forward). Hermes
then prompts the user for a search string.
A specific page number can be brought to the screen by typing ESC G, whereafter Hermes
prompts for a page number. Signed numbers are treated as relative page numbers.
Sections of the log file can be printed by typing the ESC H sequence. Hermes prompts then for a
range of pages to be printed. The default range is the page currently displayed and the preceding
two pages. By default the command to actually do the printing is ``lpr''. This can be changed
by typing ESC P, whereafter a new print command can be specified.
The statement that the COA is a viewport on the log file is not quite true. In fact the log file
and the COA are different output streams to which tasks can send information selectively.
Most tasks however send the same information to both the log file and the COA.
COA command summary
CTRL­P enter or leave page mode
CTRL­Z display previous page and enter page mode
CTRL­N display next page
CTRL­R search forward for text string
CTRL­S search backwards for text string
ESC G go to specified page number
ESC H make hardcopy of specified page numbers
ESC P change hardcopy print command
4.5.5 Running Tasks
Starting tasks and supplying parameters
Tasks can be started with or without specifying parameters. To start a task without parameters,
the name of the task must be typed in the UCA, followed by a RETURN:
taskname
To specify parameters, any number of keyword­value combinations separated by blanks can be
added to the taskname:
taskname keyword 1 =values 1 keyword 2 =values 2 : : :
This format is also used to supply parameters to an already running task.
If there is something wrong with the command, an error message is displayed in the lower right
corner of the screen.

28 Chapter 4.
Tasknames may be preceded by an explicit path. In this case, the task must be present in
the specified directory; the task path is not searched.
Tasks can be run again with (partly) the same parameters by prefixing the task start com­
mand with an exclamation mark (!). Any explicitly specified parameters supersede the corre­
sponding old parameters. For historical reasons, the previous parameters of a task are called
the task's macro.
Tasks can be run under a different name (``alias''). The command to do this is:
aliasname(filename) : : :
Aliasname is the taskname under which the task will run and filename is the name of the
task's executable file, specified in the correct case (lowercase for standard GIPSY tasks).
Aborting, suspending and resuming
Tasks can be aborted by typing CTRL­C. They can be suspended and resumed by typing CTRL­W
or CTRL­G. If more than one task is active, the target task's name must be present in the UCA.
Changing the task context
The context of a task can be changed using a pop­up menu that can be activated with the
sequence ESC S. The following context parameters can be changed with this menu:
­ error level
­ message level
­ output mode: normal, expert or test
­ screen output: on or off
­ log file output: on or off
­ hide ``hidden'' keywords: on or off
To change the context of a running task, its name must be present in the UCA. If the UCA is
empty, the template context will be changed.
Directories and paths
The working directory can be changed by typing ESC D. Hermes then prompts the user for a
new directory. This directory will then be used for tasks started after the change. Running tasks
and Hermes itself are not affected.
The task path can be changed with ESC T. Upon the prompt that follows one or more directories
or environment variables (with a leading $­character) separated by blanks can be specified.
Whenever Hermes starts a task without an explicit path, this list is scanned to find the task.
If it is not in one of the specified directories, Hermes tries to find the task in $gip exe. The
default path is `.' (the current working directory).
Inspecting keywords
The current set of keyword­value combinations of a task can be inspected by typing ESC K while
the name of the task is present in the UCA. This causes (part of) the COA to be overlaid with

Hermes. 29
a display containing the current user input parameters of the task. If the amount of space on
the screen is not sufficient to show all parameters, the user can page through the display just
like paging through the log file. CTRL­N pages forward; CTRL­Z pages backwards. To inspect its
keywords, the task need not be active.
Typing ESC K again will remove the overlay screen.
Getting help
To obtain help information about a task or about Hermes, CTRL­H can be pressed. This causes
(part of) the COA to be overlaid with a display containing the user document of the task of
which the name is present in the UCA. If there is also a keyword present (e.g. as the result of a
prompt), Hermes positions the document at the first occurrence of the keyword. If the amount
of space on the screen is not sufficient to show the whole document, the user can page through
the display just like paging through the log file. CTRL­N pages forward; CTRL­Z pages backwards.
If the COA is empty, pressing CTRL­H will display a summary of Hermes' commands.
Pressing CTRL­H again will remove the overlay screen.
4.5.6 Unix shell
Typing ESC U causes the COA to be overlaid by an Unix shell window or, if the Unix shell is
already present, causes the window to be popped down. The shell used is /bin/csh. Because
this shell is not connected to a real terminal, functionality is somewhat limited: e.g. a screen
editor would not work. Also some commands behave differently, e.g. ls produces a one­column
list. (A multi­column list can be obtained with ls ­C.)
By default information displayed in the Unix shell window is not logged. Logging to the COA
and log file can be enabled (and disabled) by typing ESC L.
The Unix shell can be completely terminated by typing exit.
4.6 xHermes
xHermes (X Window Hermes) is in a number of respects incompatible with tHermes. E.g. screen
log files have different formats, task keywords (for the automatic ''macro'') are saved in dif­
ferent ways. The current version of xhermes should be considered as the result of an exercise
in programming with the X Toolkit and the Athena widgets and as such should eventually be
discarded when a new xhermes has been developed. For this reason no major improvements of
this version will be carried out. Suggestions are however welcome; they will be useful when the
new xhermes will be developed.
4.7 nHermes
4.7.1 Introduction
nHermes (non­interactive Hermes) is the GIPSY master control program for a non interactive
environment. xHermes is based on the interactive tHermes. The user commands will be con­

30 Chapter 4.
sidered equivalent as if they were typed in the User Command Area of the tHermes. Default
values for unspecified keywords will be taken if available. If there is no default available, an error
message will be generated in a log file and nHermes will stop with the current user command.
When a user command is done, nHermes starts the next user command if given by the user.
If a time out option is set, a time out will occur after the user supplied number of minutes
and nHermes stops with the user command it is dealing with at that time. The time out works
separately for each user command. All output will be kept in a log file.
4.7.2 Syntax
The syntax for starting nHermes is:
nhermes [\Gammal ! log f ile name ?][\Gammat ! minutes ?]! user command ?
The options may appear in any order and may be intermixed with the user commands. The ­l
and ­t flags are optional.
The log file will always have the extention .LOG and it contains a history of all operations done
and the information generated by servant processes. The information in the log file which is
generated by servant processes depends on the settings of those processes. If you don't give the
extention in uppercase or not at all, it will be added to ! log f ile name ?. The default log file
name is GIPSY.LOG.
The time out option provides termination of the user command when it is stucked in an endless
loop. ! user command ? can be a cola script or a name of a servant task with their parameters.
COLA is a small (but powerful) high­level control language for use with Hermes. Using COLA
you can write a program to execute a sequence of commands.
The name of the servant task or the cola script with the parameters should be suitably quoted
or escaped to keep it together (e.g. between double quotes). If the given servant task or cola
script with their parameters are not suitably quoted or escaped to keep it together, nHermes
handles them as if they were separate user commands.
A cola script file must have the extention .col as specified in the documentation of the application
program COLA. You may give the name of the cola script with or without the extention .col to
nHermes.
ffl Example:
nhermes \GammalMylog ''FLUX, INSET=cg1517 v ''
Let 'nhermes' start task FLUX on all subsets of set cg1517 and put results in file My­
log.LOG.

Hermes. 31
CONTROL KEY DEFINITIONS
HELP
CTRL­H ­ provide help display. If a task name is present in the user command area,
the dc1 document of that task is displayed. If there is also a keyword
present, then the display is positioned at the first occurrence of the
keyword in the document. When CTRL­H is pressed for a second time,
the help display will disappear.
CTRL­N ­ page forward in the help display.
CTRL­Z ­ page backwards in the help display.
CTRL­R ­ reverse search for a text string in the document.
CTRL­S ­ forward search for a text string in the document.
SESSION CONTROL
CTRL­L ­ refresh the terminal screen.
CTRL­O ­ circulates between terminal windows waiting for keyboard input.
CTRL­Q ­ prompts for user's approval to quit. 'Y' terminates the GIPSY session.
If any tasks are still active, THermes waits until they are finished. Any
other character causes the session to be continued.
TASK CONTROL
CTRL­C ­ abort a task; the task name must be present in user command area
(UCA).
CTRL­W ­ suspend or resume a task (name must be present in the UCA).
Esc S ­ change running parameters, e.g. output mode. If a task name is present
in the UCA, then this task is affected, otherwise the default settings for
new tasks are changed.
Esc K ­ display the current user input parameters of the task of which the name
is present in the UCA. The task need not be active. Pressing Esc K
again removes this display.
Esc D ­ change working directory.
Esc T ­ change 'path' for tasks. A path consists of one or more directory speci­
fications, separated by blanks.
Table 4.1: HERMES commands

32 Chapter 4.
COMMON OUTPUT AREA
CTRL­N ­ page forward in the common output area (COA).
CTRL­Z ­ page backwards in the COA.
CTRL­R ­ search backwards for text in the COA.
CTRL­S ­ search forward for text in the COA.
CTRL­P ­ switch page mode on or off.
Esc G ­ go to absolute or relative (+/­) page number.
Esc H ­ make hardcopy of screen pages to printer (default: current page)
Esc P ­ change printer command for Esc H (default: ''lpr'')
COMMAND LINE EDITING
CTRL­A ­ move to start of user command area (UCA).
CTRL­B ­ move one position backwards.
CTRL­D ­ forward delete one character.
CTRL­E ­ move to end of UCA.
CTRL­F ­ move one position forward.
CTRL­K ­ forward delete rest of command.
CTRL­U ­ clear UCA.
DEL ­ backward delete one character.
CTRL­T ­ replace UCA contents with the next active task name.
Space ­ if the UCA is 'free', replace it with the next prompt for user input.
UNIX SHELL
ESC U ­ pop up and down UNIX shell (terminate with exit.
ESC L ­ logging on/off to COA and log file.
MISCELLANEOUS
ANSI escape sequences recognized by Hermes:
Key ­ Equivalent
left arrow ­ CTRL­B
right arrow ­ CTRL­F
up arrow ­ CTRL­T
page up ­ CTRL­Z
page down ­ CTRL­N
Table 4.2: HERMES commands (cont.)

Chapter 5
General GIPSY programs
5.1 Introduction
This chapter describes the most often used general utility programs available within GIPSY.
For each program a short description is given of the most important keywords and their use
in standard cases. More information can be found in the standard GIPSY documentation files.
You can print these files using standard print commands. You can always get help from within
GIPSY using the HERMES help command (!Ctrl?H).
The programs are treated more or less in the order in which they are needed; getting data (i.e.
listing and reading tapes, making maps), finding your way on disk (listing disk contents, looking
at headers), basic set manipulation, plotting and printing etc.etc.
5.2 Getting data into GIPSY
LFITS
The program LFITS lists FITS (Flexible Image Transport System) files on magnetic tape or disk
and gives one­line descriptions of their contents. The program first asks to specify the input
device with TAPE=. Here the name of a tape unit can be entered. For example,
TAPE=MAG0
Also, the name of a subdirectory on disk can be given. For example,
TAPE=../Gipsy/FTSfiles
where ../Gipsy/FTSfiles is the name of a subdirectory owned by the user. In this subdirectory all
files with the names filexxxxxx.mt (where x can be any digit) are assumed to be FITS files.
Next, LFITS selects the numbers of the files to list with FILES=. As a default, all FITS files are
listed.
RFITS
RFITS transfers FITS files from tape to GIPSY data sets on magnetic disk. Like LFITS it first
33

34 Chapter 5.
asks for a tape unit from which to transfer the data, with INTAPE=.
Subsequently filenumbers which are to be loaded onto disk can be specified using INFILES=. The
number of the first file found on tape is zero. Thus when the tape has been wound forward to
e.g. the middle of its total length, RFITS will continue forward until it finds a begin of file, and
then assume that that file is number zero. The numbers of all following files are relative to this
one. To transfer more than one FITS file to one GIPSY set, supply INFILES= with a series of
file numbers. For example,
INFILES=0 3 4
or
INFILES=5:10
To allow more than one transfer, RFITS repeats the keyword INFILES= until a carriage return is
given. Since RFITS reads a tape in forward direction, the input numbers must be in ascending
order. Each input to INFILES= is followed by a series of keywords to specify the output set.
To select the output set name, RFITS prompts with OUTSET=. This keyword allows an existing
set name as input.
Subsequently, the program asks (hidden, unless AUTO=Y ) information on the axes, repeating
a series of keywords for each axis. The last character of these keywords always indicates the
number of the questioned axis (e.g. NAXIS2 contains the number of pixels on the second axis).
In the following, this character is represented as an asterisk.
In automatice mode RFITS will do its best to comprehend the FITS structure on
tape. FITS items for which the program has some reasonable defaults will not be
asked. In non­automatic mode ( AUTO=N ) all items will be asked.
CTYPE*= requests the axis name. If an existing set is supplied as output set, RFITS tries to
provide by default the name of the corresponding axis in the set. For a not yet existing set,
RFITS can provide by default the axis name in the FITS file, if this is a correct GIPSY axis
name. Axes having an extension of one can be abandoned, by giving SKIP, or hidden, by giving
HIDE. The only remainder of a hidden axis in the output set is a descriptor item telling that it
is a hidden axis. SKIP and HIDE can appear as default values too.
If the units of the axis are not available in the FITS header, RFITS requests them with the
keyword CUNIT*=. For example,
CUNIT1=m/s
Then the program asks, with the keyword CRVAL*=, to enter the value in physical units of the
reference pixel on the axis. The reference pixel is the pixel with value zero. For example, for a
FREQ axis,
CRVAL3=2000
Next, the distance in physical units between pixels on the axis has to be set using CDELT*=.

General GIPSY programs. 35
To specify the range in grids along the axis the keyword LIMITS*= can be used. Note that sets,
once they are created can only be extended along their last axis, so make sure the area specified
with LIMITS*= is large enough for your purposes.
The first grid position on the axis is set with GRID*=. The values given to GRID*= and LIMITS*=
determine the reference pixels in the output set. E.g., if
LIMITS1=15 GRID1=\Gamma7
then the reference pixel for the first axis is 8.
If a data set has a frequency axis, the frequencies in principle can be converted to velocities if
the relevant rest freqeuncy is known. RFITS requests the rest frequency of observation in Hz,
with FREQ0= if it is not found in the FITS header. For example,
FREQ0=1400
If the FITS file was written by the old VMS GIPSY, the velocity of the first grid on the velocity
axis is asked for with VEL=, e.g. VEL=20 .
CREATE
The program CREATE creates a set and fills it with user defined values. The program starts
with prompting for a set name, with the keyword INSET=. If the name of an already existing
set is entered, the program returns with the keyword DELETE=. Answering with YES results in
deletion of the existing set. Giving a return lets CREATE prompt again with INSET=.
Next, the program requests the instrument of observation, with INSTRUME=. For example,
INSTRUME=VLA
CREATE asks then to specify the axes, prompting with a series of keywords for each axis (like
in RFITS). The last character of these keywords indicates the axis number. Below, an asterisk
represents this character.
First, an axis name has to be assigned to CTYPE*=. E.g.,
CTYPE1=RA
The next keyword NAXIS*= selects the size of the axis in grids. For example,
NAXIS1=15
Then, the reference pixel of the axis (having physical coordinate CRVAL*=) is asked for, with
CRPIX*=. For example,
CRPIX1=8
Subsequently, supply the physical units of the axis to CUNIT*=. For example,
CUNIT1=m/s
and next give the value in physical units at the reference pixel with CRVAL*=. E.g.,

36 Chapter 5.
CRVAL3=2000
The keyword CDELT*= requests the increment in physical units per pixel. For example,
CDELT1=1
Only for a DEC axis, CREATE asks to specify the rotation angle of the axis in degrees, with
CROTA=. Its default is zero.
For a FREQ axis, CREATE prompts with the keywords DUNIT*=, DRVAL*=, and FREQ0=. To
specify the secondary units etc. of a FREQ axis. Answer FREQ0= with the rest frequency in Hz.
This series of keywords is repeated until !CR?is given to CTYPE*=.
After entering all information on the axes, fill the set with values by assigning a mathematical
expression to FUNCTION=. Parameters in the expression are the axes names assigned to CTYPE*=.
For all functions, constants, and operators allowed in the expression, see the document create.dc1.
A sample expression is
FUNCTION=RA + DEC/100
5.3 What is on disk?
DISK
The program DISK gives a list of the sets in the current directory. Furthermore, some information
on particular sets can be obtained.
A set consists of astronomical data and their header information. Its structure compares to an
n­dimensional array. A subset of a set is an m­dimensional part of it, m being smaller than or
equal to n. A frame is a part of a subset, but it has for one or more of its dimensions not the
full range of values of that dimension.
To start the program, enter its name; DISK!CR?. Then, DISK displays an overview of the sets
in the current directory as shown in Table 5.1.
Note that DISK truncates names more than fifteen characters long. For example, AVERYVERY­
LONGNAME becomes AVERYVERYLONGNA...
After giving the listing, DISK prompts with INSET= for the name of a set on which you want
more detailed information. For example,
INSET=VELRES
For this set DISK displays more detailed information.
DISK repeats prompting with INSET=. A carriage return stops the program.
This program has a hidden keyword PRINTER=, allowing for sending its output to a printer. To
use this option, start up DISK as follows.
DISK PRINTER=0
DISK shows a menu of available printers on the screen (see Table 5.2).
Then, a choice can be made. For example,
PRINTER=3

General GIPSY programs. 37
***DISK***
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
nr SETNAME descr image Axis name(s) and size(s)
(kb) (kb)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
1 3DSET 48 10 (RA,DEC) = (60,40)
2 4DIMSET 48 40 (FREQ,RA,DEC,PARAM) = (10,10,10,10)
3 ANTENNA 48 40 (RA,DEC) = (100,100)
4 AS4 48 1 (RA,DEC,FREQ,NEWPAR) = (5,5,2,3)
5 AURORAMOMENTS 48 10 (RA,DEC,PARAM) = (20,20,6)
6 BLANKSET 48 19 (RA,DEC,VEL) = (40,40,3)
7 ASUPERLONGNAME... 48 1 (RA,DEC) = (10,10)
8 FITDAT 48 1 (RA) = (16)
9 GAUSS 48 40 (RA,DEC,FREQ) = (100,100,1)
10 GOODLOOK 48 767 (RA,DEC) = (415,473)
11 HISTOGSET 48 1 (PARAM,PARAM) = (10,10)
12 KGB2 48 11 (DEC,PARAM) = (1014,3)
13 VELRES 48 108 (RA,DEC) = (131,211)
14 n1260s60 48 896 (RA,DEC,FREQ) = (128,128,14)
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
Descriptors: 672 kb
Images : 1938 kb
Directory : 2614 kb
­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­
Table 5.1: Sample output of DISK
HEADER
The program HEADER displays header information on a set and its subsets. The program
prompts for an input set (and subsets) with the keyword INSET=. If only a set is given, HEADER
returns header information on the set as a whole. If one or more subsets are specified, only
header information pertaining to these subsets is provided. Information not available at subset
level is searched for at higher levels. For example, typing
INSET=VELRES
will produce a header listing as given in Table 5.3.
To obtain a hard copy of the output you can use the hidden keyword PRINTER= as described
under DISK (see also Table 5.2).

38 Chapter 5.
==============================PRINTERS=============================
nr name cols rows comment
===================================================================
1 textprinter 77 64 Laserprinter in room ZG92A
2 lineprinter 132 60 Printer in room ZG170
===================================================================
Table 5.2: PRINTER= menu
FIXHED
The program FIXHED adds, changes, and deletes (sub)set header items. Below, these options
are described separately.
First, assign an input set (and subset(s)) to INSET=. Then, FIXHED prompts for the name of
the header item to work on, with the keyword ITEM=. There are two reserved names, HEAD
and LIST. To list the header items present in the specified set or (sub)set(s), give
ITEM=HEAD
FIXHED displays the items, in the format: item name, value, and, if available, FITS style com­
ment. A typical section of FIXHED output is shown in Table 5.4.
The descriptor items in GIPSY programs are partly FITS keywords, partly keywords defined
by GIPSY programmers and users themself. A list of the most used descriptor items can be
obtained by typing
ITEM=LIST
FIXHED displays then the items, in the format: item name, meaning, and, optionally, possible
values. For example,
BUNIT : data units (WU, MJY/SR, ...)
where BUNIT is the item name, data units its meaning, and WU and MJY/SR are examples of
possible values.
FIXHED allows for repeated input to the keyword ITEM=. Pressing !CR? stops the program.
See now the option of your choice.
Add
To add an item to the specified (sub)set(s), assign the item name to the keyword ITEM=. For
example,
ITEM=BUNIT
If necessary, consult the list of items used by GIPSY to find the name of the intended item (See
the option ITEM= LIST explained above). It is recommended to use item names already available

General GIPSY programs. 39
*****************************************************************************
Set: VELRES top level 26­FEB­1992
Observer: BROEILS Obs. date: / / Object: N1560
Obs. type: POLN Instrument: WSRT Polarization: XX
Map center: (Epoch: 1950.0)
RA : 66.75 DEGREE = 4 h 27 m 0.00 s
DEC : 71.80 DEGREE = 71 d 47 m 53.99 s
Axis length and range:
RA : 131 [­70, 60]
DEC : 211 [­120, 90]
Grid spacing:
RA : ­0.001390 DEGREE = ­5.004000 arcsec
DEC : +0.001390 DEGREE = +5.004000 arcsec
Data range = [­31.7353,37.884 ] (km/s) Number of blanks: 0
*****************************************************************************
Fringe stopping center RA = 66.75 = 4 h 27 m 0.00 s
DEC = 71.80 = 71 d 47 m 54.00 s
Pointing center RA = 66.75 = 4 h 27 m 0.00 s
DEC = 71.80 = 71 d 47 m 54.00 s
Rest frequency **** Interferometers 40
Total bandwidth 2.50000 MHZ Polarizations 2
Channel separation **** Frequency points 128
Center velocity **** Taper HANNING
Minimum baseline 36.0 meter Tape volume P92758
Maximum baseline 2735.8 meter Tape label 39
Beam (FWHM) = **** x ****
Position angle major axis (N­?E): ­0.74 degrees
Antenna pattern: ****
HISTORY/COMMENT
===============
....
*****************************************************************************
Table 5.3: HEADER output

40 Chapter 5.
HEADER at top level
===============================
APLAB = ' 0 ' / tape label of Antenna Pattern
APVSN = ' ' / tape volume of Antenna Pattern
BANDW = 2.500000E+00 / total bandwidth of observation
BLGRAD = 'B ' / baseline grading function
BMPA = ­7.441014E­01 / pos. angle of major axis of beam (N­?E)
BUNIT = 'km/s ' / Units of data
CDELT1 = ­.13900000000000D­02
.
.
.
UVGRID = 'P ' / convolving function code
VEL = 6.658606E+01 / velocity (km/s) of V=0
ZGRID = ­7.441014E­01 / grid unit of subset
HISTORY/COMMENT
===============
.......
Table 5.4: FIXHED, ITEM=HEAD output
in GIPSY; a program needing the header information on the maximum value in a set searches
for the header item DATAMAX; items with the same content that have other names are ignored.
In case a new item name is entered, FIXHED requests that you select the type, with the keyword
TYPE=. The types available are
ffl I(nteger), e.g., to store the number of interferometers used in an observation
ffl R(eal), e.g., to store the maximum of a set
ffl D(ouble), e.g., to store the total bandwidth of an observation
ffl L(ogical), seldom used
ffl C(haracter), that is, a character string, e.g., to store the date of observation
ffl T(ext), that is, one or more character strings, e.g., to store the set and subset used for an
antenna pattern
ffl H(istory), text type, reserved for the items COMMENT and HISTORY
If the fictitious item name ODDNAME was introduced, input could be, for example,
TYPE=Double

General GIPSY programs. 41
or
TYPE=T
meaning text type.
Furthermore, a value is associated with the item, by specifying the keyword VALUE=.
The keyword COMMENT= can be used to enter a FITS style comment. For example, if the item to
be added is NINTF, input can be
COMMENT=number of interferometers used
A carriage return results in no comment. FIXHED does not prompt with COMMENT for items of
text or history type.
When FIXHED is working on a series of subsets, it prompts with the keywords VALUE= and
COMMENT= for each individual subset. To provide remaining subsets with the same input to these
keywords as the current subset, use the hidden keyword ALL=. For example,
VALUE=15 ALL=Y
To stop the program from adding the descriptor item to remaining subsets, give
VALUE=!CR?
Change
To change a descriptor item, enter the item name. For example,
ITEM=DATAMAX
FIXHED then requests that you change the value of this item, with the keyword VALUE=. A
carriage return leaves the value unchanged. For the items HISTORY and COMMENT, the program
first displays the old value, line by line. See the following example of an item of HISTORY type.
subset nr.1
1: DUMMY SET FOR TESTING 30/4/1991
2: MINOR CHANGES 10/5/1991
The keyword LINE= asks for the number of a line to be changed. Then, VALUE= has to be specified
for the entered line number. FIXHED keeps prompting with LINE until a carriage return is given.
For example,
LINE=1
VALUE=DUMMY SET FOR TESTING PROGRAM HEADER 30/4/1991
LINE=3
VALUE=DATAMIN ADDED ON FREQ SUBSETS 12/5/1991
LINE=!CR?
Subsequently, FIXHED allows for changing the FITS style comment. The program displays the
old comment and prompts for a new one, with the keyword COMMENT=.
When FIXHED works on a series of subsets, it requests input to the keywords VALUE= and
COMMENT= for each individual subset.

42 Chapter 5.
Delete
To delete a descriptor item, its name has to be entered. Also, the option D(elete) has to be
assigned to the hidden keyword MODE=. For example,
ITEM=DATAMIN MODE=D
When the keyword INSET= was supplied with a set name only, then the program asks if the
specified header item has to be deleted on all lower levels too, with ALL=.
Next, FIXHED asks for a confirmation of the intended deletion, with the keyword OK=. When
a series of subsets was assigned to INSET=, the program prompts with OK= for each individual
subset. To delete the header item for all remaining subsets, type
OK=Y ALL=Y
To leave the item attached to all remaining subsets, answer OK= with a carriage return.
DELETE
The program DELETE deletes sets in the current directory. DELETE first requests, with the
keyword INSET=, to specify the name(s) of one or more sets to delete. For example,
INSET=GAUSS LOOK4
To check if it indeed has to delete these sets, DELETE prompts for each individual set with the
keyword OK=. The default is NO. The name of the set prompted for is displayed in the status
area. E.g.,
Ok to delete GAUSS ? [Y/N]
Then, DELETE repeats asking, with the keyword INSET=, for sets to delete. A carriage return
stops the program.
5.4 Displaying data
GIDS ( Groningen Image Display Server ) is the application you need to display your 2­
dimensional (sub)sets. It can be started with INIDISPLAY or with VIEW (which needs a (sub)set).
Using GIDS is very simple. With your mouse (and one of its buttons) you select actions like
zooming, scaling in the window with the menu bars. Move the mouse pointer in one of the menu
boxes and click with one of the mouse buttons. An action is started or a sub menu appears. In
the upper left corner of the GIDS window there are 7 boxes containing relevant information.
Example:
1 AURORA Name of the image.
2 5168.24 KM/S The physical value of the current subset.
3 REC= 7, 4, 3 Seven images of current size can be stored,
you have stored 4, and you are looking at number 3.
4 MASK= 0 ON= 15 Future use.
5 VAL= ­1.786E­2 The value of the pixel you are pointing at.
6 POS= ­2, 5 The position in grids of the pixel you are
pointing at.
7 ... A text box in which you can enter numbers of
recorded images for looping etc.

General GIPSY programs. 43
Some of the GIDS options are not yet implemented (for example Region ) others need a little
extra information. For interactive work the Cursor option is handy. If f.i. you are displaying
an image and want to run STAT, the keyword BOX= can get its values manually or with your
mouse buttons.
Button Action
left enter grid coordinates of mouse position in the UCA of tHermes.
middle interactive definition of a box. The size of the shape is
determined after this button has been released.
right return the coordinates of a previously defined box in
the UCA of tHermes.
Table 5.5: Mouse actions using the Cursor option in GIDS
After clicking Etcetera and Recording there are options for recording a limited number of
(sub)sets, viewing those images, blinking two images, looping over a number of images (movie,
see VIEW) and splitting an image.
VIEW
The program VIEW displays two­dimensional (sub)sets. First, VIEW requests that you specify
the set (and subset(s)) it has to display, with INSET=.
Then, so­called ``clip levels'' can be set, a lower and an upper clip level, by specifying CLIP=.
Only values falling within the range specified by these levels are displayed. For example,
CLIP=0 15
displays only pixel values between zero and fifteen.
If no display window is available VIEW will create one, asking the user specify a position for that
window on the screen. Next VIEW displays the first image (subset) . If more than one subset
was assigned to INSET=, then VIEW asks for each of the remaining subsets whether it has to be
displayed or not, with the keyword NEXT=. The default is YES. Giving NO stops the program.
VIEW allows recording of images to create a ``movie'' of successive images (subsets). Then, start
the program together with a specification of the hidden keyword RECORD=:
VIEW RECORD=Y
Now, VIEW prompts with the keyword NEXT= only once: after the display of the first image, for
all the remaining images. All images are positioned the way the first one is positioned. In GIDS
a movie can be started after you have specified image numbers in the text box and clicked the
'loop' button. The display rate is adjusted by positioning your mouse in GIDS and clicking the
left mouse button. In GIDS, recordings can be done manually also.

44 Chapter 5.
5.5 Plotting data
An application is able to create a plot if it prompts with the keyword GRDEVICE=. The default
is a list of devices. Examples are:
X : Tektronix window on screen (b&w)
L1LASER : QMS laser printer in landscape mode
P1LASER : QMS laser printer in portrait mode
LCOLOUR : Colour printer in landscape mode
PCOLOUR : Colour printer in portrait mode
GIDS : Gids window on screen (colour)
NULL : null device (no plot output)
Programs like CPLOT and STAT and lots of other applications capable of plotting, all share
this keyword. Usually you will enter X to plot in a Tektronix window (which is automatically
generated then) on your screen. If you like your results, send it to a printer by changing the
device (f.i. in STAT) or rerun the program with for example !STAT GRDEVICE=P1LASER . After
the application is finished, a plot is sent to the QMS laser printer in portrait mode.
CPLOT
Introduction
Among standard ways of presenting astronomical data are contour and grayscale plots. If a map
is represented by f(x,y), contours are lines of constant f. This requires the data you want to
present with this program must be 2 dimensional. Therefore sets with more than 2 axes need a
subset specification at INSET=. Information about the syntax can be found in the GIPSY users
manual. The names of the axes can be found with the programs HEADER or DISK. If only a
part of the data need to be displayed, use BOX= with four arguments to decrease the size. Input
can be a lower and an upper coordinate pair, a coordinate pair and combination with physical
coordinates. See the GIPSY user manual for the use of physical coordinates. If you want to
display more than one subset of a set INSET=AURORA F 1:10 ) you get each subset on a blank
screen or paper (advancing to a new page or clearing the screen is controlled by the NEXT=!CR?
keyword) unless you want to display all the data in a mosaic. With MOSAIC= you can give the
number of rows in the mosaic. The program calculates the number of columns. The first plot
will be in the upper left corner of the screen or paper. Each subset in a mosaic will now be called
'subplot'.
Contours
The contours at CONTOUR= are a series of floating point numbers given in units of your map. This
keyword obeys the syntax for reals as described in the GIPSY user manual. This includes the
use of expressions also. An example could be CONTOUR=LOG([10:1000:50]) which is evaluated to

General GIPSY programs. 45
1, 1.77815, 2.04139, 2.20412, ...., 2.98227
Contours will be plotted with the same line width as the axes of your plot. The blanks in your
data are ignored, making gaps in the contour map. The contour levels can be given in percentages
also. To put input in percentage mode, select PERCENT=Y . The conversion from percentages to
absolute levels is done with the formula:
level[i] = min + perc[i]=100 \Lambda [max \Gamma min]
so that 0the level 'max'. The values min, max are the minimum and maximum values of the
data as recorded in the header of the current sub)set. If you don't trust these values or if your
box is smaller than the entire (sub)set, use CALCMNMX=Y to calculate these values. The min and
max are also calculated if PERCENT=Y and no header items descriptorDATAMIN and DATAMAX
are found in the header. If the number of given contours is greater than 1, you can select a
contour style to distinguish negative from positive contours ( STYLE=N ) by default, or odd from
even contours ( STYLE=O ). If you want all contours to be solid, use STYLE=S. Contours are
associated with a color index. This index is an integer number that corresponds to a device
dependent color. For a color plot you can use in COLIND= the color indices:
0 Background
1 Default (Black if background is white)
2 Red
3 Green
4 Blue
5 Cyan
6 Magenta
7 Yellow
8 Orange
9 Green + Yellow
10 Green + Cyan
11 Blue + Cyan
12 Blue + Magenta
13 Red + Magenta
14 Dark Gray
15 Light Gray
16­255 Undefined
The number of color indices must be equal to the number of contours. If COLIND=!CR? the

46 Chapter 5.
indices are calculated by the program. If at least one value is given but the number of indices is
less than the number of contours, the remaining indices are copied from the last one specified.
For a black and white hardcopy you can use 0 for a white contour and 1 for a black contour. This
combination is sometimes used to emphasize the contours in dark regions of a gray scale plot.
If the device is the screen, the color indices will not be very useful. The width of the contours
is controlled by CWIDTH=. Together with keywordLINEWIDTH= and keywordPLATT=, these
keywords control the width of the lines to be plotted. The smallest number is 1 the largest
possible number is 21. The CWIDTH= keyword is asked hidden just before plotting a contour,
making it possible to draw different contours in different widths. The default values of all the
keywords containing widths is 1 if the plotting device is the screen or 2 if it is a hardcopy device.
Example: CWIDTH=4;3;2;1 The lowest contour has width 4, the highest has width 1. The semi
colons are important here because CWIDTH= accepts only one number at a time.
** Trick:
If the minimum value 1 is too thick on paper, there is a possibility to set 'setlinewidth' in your
postscript file to a smaller value.
Devices
The destination of the plot is selected with GRDEVICE= If you give !CR? only, you get a list of
devices that can contain for example:
X : Tektronix window on screen (b&w)
L1LASER : QMS laser printer 1 in landscape mode
P1LASER : QMS laser printer 1 in portrait mode
LCOLOUR : Colour printer in landscape mode
PCOLOUR : Colour printer in portrait mode
GIDS : GIDS window on screen (colour)
NULL : null device (no plot output)
etc...
On some printers it is possible to plot on a transparency instead of paper. Instructions are
obtained at local system management.
Gray scales
Instead or along with drawing contours, it is also possible to fill your plot with shades repre­
senting the image values. The shades are given in GRAYSC=. The maximum number of shades is
128. Again, input values are floating point numbers and expressions are allowed. The scales are
in units of the map and must be in ascending order. Example: GRAYSC=2 3.5 8 Image values

General GIPSY programs. 47
smaller than 2 are white in the plot. Values equal to or greater than 2, but smaller than 3.5 get
the first shade of gray, values 3:5 Ÿ f(x; y) ! 8 get the second shade of gray and values – 8
are black in the plot. The available number of different shades depend on the selected device. If
PERCENT=Y , the gray scale values are percentages.
** Hint
If you want to fill contours smoothly with gray scales, contours can intersect the 'gray scale
pixels') simulate more pixels by regridding the map. Use fprogramREPROJ with changed grid
spacings to achieve this effect.
Layout
A plot consists of a title along the lower x­axis and left y­axis, a space for labels containing
positions in physical coordinates, a grid margin to reserve space for plotting positions in pixels,
the plot itself and an area where important information about the plot is displayed.
Titles
The default titles along x and y axes are the names of these axes as found in the header. Titles
can be altered with XTITLE= or YTITLE= The keywords accept text strings. A string can contain
escape sequences. These are character­ sequences that are not plotted, but are interpreted as
instructions. All escape sequences start with a backslash character (n).
``u Start a superscript or end a subscript;
``d Start a subscript or end a superscript;
(u and d must always be used in pairs)
``b Backspace, i.e. do not advance text pointer after
plotting the previous character;
```` Backslash character;
``A Angstrom symbol;
``gx Greek letter corresponding to roman letter x;
(Lower case and upper case x give different greek
characters )
``fn Switch to Normal font
``fr Switch to Roman font
``fi Switch to Italic font
``fs Switch to Script font
Like all 'plot' text, the text can contain so called PGPLOT symbols. Available symbols (ú
1000) are arranged according to Hersey's numerical sequence and are listed in Table B.1 of the
PGPLOT manual. Any character can be inserted in a text string using an escape sequence of
the form n(n), where n is the 4­digit Hersey number. The positions of the titles are calculated
by the program but can be altered with XTPOS= and YTPOS=. Each keyword accepts a coordinate

48 Chapter 5.
pair in mm. The numbers are absolute positions in the plot. If for some reason there is not
enough space along the axes to place the title, increase the default values (10 mm in x and y
direction) at TITLEMARGIN= If only one number is given, the y value is automatically copied
from this value.
Position in pixels
Positions along the axes can be in pixels and physical values. If GRID=Y , each 10th pixel
position will be marked inside the plot box. There is some room reserved default 4 mm in x
and y direction) for plotting the numbers. This space is controlled by the keyword GRIDMARGIN=
which accepts two numbers for space in x and y direction. If only one number is given, the y
value is copied from this value. If GRID=N (default) there are small grid margins.
Physical values
The labels along the axes indicate the physical positions i.e. if transformation from pixels to
physical coordinates is possible. If transformation is not possible, the possible reason is mentioned
in your log­file. There the program puts the result of transformation of pixel 0 to a physical
position. Conversion always take place to the primary axis units as found in the header (CUNIT#).
If there are also secondary units, the program will convert the pixels to these units. The default
separations between two positions is calculated by the program. A position label is plotted
together with a marker called a Tick. Space between two are controlled by TICK=. It accepts
values for the x and y direction overruling the calculated default values. Negative numbers will
be converted to positive numbers. The units are the axis units except if the header unit was
'DEGREE'. The values are in seconds of arc then. If an axis is the RA axis of an unrotated
map, the TICK= units are in time seconds. Between two major tick marks there are minor tick
marks. The default number is calculated by the program. The numbers of minor ticks in x and
y direction can be changed with NMINOR= If you don't want minor tick marks, use NMINOR=0 0
It is possible to plot labels for all axes, but in most plots only the lower x axis and the left y axis
do have labels, while the others have ticks only. For a single plot this is the default labeling. In a
mosaic, lines connecting two 'subplots' have tick marks only. The decision to plot ticks or labels
is made after AXMASK= The keywords accepts 8+1 entries. An entry is Y or N. The first four
values indicate the plotting of ticks and the second four indicate the plotting of labels. Default
is AXMASK=Y Y Y Y Y N N Y y
Counting of the axes is anti­clockwise and starts with the lower x­axis. The last value indicates
plotting of ticks along axes shared by two plots in a mosaic. The default is Y. If you change
this to N, there will be no ticks on the 'inside' axes of a mosaic. Space for the labels along both
axes is calculated, but it is not known to the program beforehand how large the labels along
the y axis are going to be. Therefore sometimes the space between these labels and the y title is
to big. The spacing is controlled with LABELMARGIN= which accepts two values. The first is the
space in mm in the x direction (for the y­labels) and the second is the space in the y direction.

General GIPSY programs. 49
Rotated images
Along spatial rotated axes, only offsets are plotted. An offset is wrt. a point in your map which
is pixel 0 if this pixel is inside the box or the central pixel if pixel 0 is not in the box.
Scales
The plot is scaled in some way to fit on paper or screen. First the physical size in mm of the
device plot area is determined. From this number the margins for grids, labels titles and info is
subtracted. This number is divided by the number of subplots in one of the directions and is
scaled onto the number of pixels in that direction . After a correction for the grid margin we
end up with a scale in grids/mm. Changing these values can be done with SCALE= but then the
scales are converted to units/mm. These units are the physical units as found in the header,
only if the units are 'DEGREE', the scale input must be in ARCSEC/mm then. If both axes
have the same units, then the scales are made equal in both directions.
Plot information
Information about plot characteristics is placed in the log file and some is also placed in the
plot. The keyword that can be used here is PLOTINFO= which is N for the screen and Y for
other devices. Note that this parameter also influences the scaling in your plot. Info in the plot
contains items like the object name, the set name, used box, units, scales etc. It can be extended
with a user supplied comment in INFOCOM= which is asked in a loop that is aborted with carriage
return.The info is closed with a time stamp which is also placed in the log file so that you're
always able to find the corresponding information in the log­file (GIPSY.LOG).
Marking of positions
Positions in a plot can be marked. The positions are taken from MARKPOS= The keyword is asked
in a loop and canceled after each specification. In this way it made suitable for using so called
recall files. Example: MARKPOS=!mypos
and mypos.rcl contains:
* 29 30 45 * 4 10 40
* 29 30 30 * 4 10 0
......
Each physical position in the recall file will be marked as long as it is contained in BOX= Maximum
number of positions is 512. Each position is marked with a symbol as selected with MARKER=
Such a symbol is called a Graph Marker and is associated with a symbol number. The symbol
number can be: ­1 to draw a dot of the smallest possible size; 0­31 to draw any one of the symbols
in figure 4.1 of the PGPLOT manual; or 33­127 to draw the corresponding ASCII character.
Examples of symbols are:

50 Chapter 5.
1 dot
2 plus
3 star
4 circle
5 cross
6 square
.. .....
17 small circle filled up
28 Arrow Left
29 Arrow Right
30 Arrow Up
31 Arrow Down
Markpos accepts at most the same number of symbol numbers as there are positions given within
the box.
Beam
The process of drawing a beam in your plot is started with the keyword BEAMPOS= which accepts
a coordinate pair either in pixels or in physical units. Default, the program reads the FWHM and
position angle from the header and calculates the minor and major axis of the beam by dividing
the header values (degrees) by 7200 to get a value in seconds of arc. The FWHM is read from
header items BMMAJ and BMMIN and the angle (in degrees wrt the north) from BMPA. However
if the items are not found in the descriptor, you are prompted to give the values yourself. If
you want to overrule the defaults use BEAM= for major and minor sizes in seconds of arc, and
BEAMPA= for the position angle in degrees. The beam is shaded with straight lines with default 1
mm separation and with an angle of 45 degrees wrt the major axis. Keyword BEAMATT= accepts
three values: first value is the 'erase' variable. Default it is set to 0, and nothing happens with
the beam, but when it is set to 1, the area in a box containing the beam will be erased with the
background color. On screen however you will see the outline only. The second value is the line
separation in mm and the third value is the angle in degrees. Default, the beam in a mosaic is
plotted in the last subplot, but this can be altered with BEAMNUM= which accepts at most the
maximum of subplots integer numbers. Subplot 1 is the upper left plot. If the map is not a
spatial map, the beam is replaced by error bars. The default lengths will be the grid spacing in
units as found in the header.
Plotting the physical value of the subset
If the set has more than two axes, and a coordinate transformation is possible, you can print
the physical value of a subset in the plot. For this you use PLSUB=Y The number of decimals to
be printed is controlled by DECIMALS= which has default 2. The default position is somewhere in
the upper left corner, but if you want a different position, use SUBPOS= with a position in pixels
or physical coordinates. The position of the text applies to all the subsets in a mosaic. The units

General GIPSY programs. 51
are the units as found in the header. If there is a secondary axis defined in the header, the units
that correspond to that axis are used. The units are returned to your log­file.
Comments in plot
With keyword COMMENT= you can put strings in your plot. The keyword is prompted only if
previously COMPOS= was defined. As with other positions, COMPOS= expect you to give a coordinate
pair either in pixels or in physical coordinates. A loop is started now. For each specification of
COMPOS= there is a COMMENT= prompt. The keyword accepts the so called Hersey symbols also.
The loop is aborted with COMMENT=!CR? . Each comment can be in different height, width, font
etc. These so called text attributes are connected with the text attributes keywords. The text
string can also contain escape sequences. These are character­sequences that are not plotted,
but are interpreted as instructions.
Text attributes keywords
Input are 7 floating point numbers that control the appearance of the text to be plotted. The
input syntax is:
XXXXXATT=Hght,Wdth,Fnt,Jstf,Era,Angl,Col [x1,..,x7]
More specific:
Hght: Character height
It's a normalized value corresponding to about
1/40 of the height of the plot device.
Wdth: Thickness of chars and lines (1..21):
Fnt: Font type 1,2,3, 4:
1 single stroke ''normal'' font
2 roman font
3 italic font
4 script font
Jstf: Justification of text: 0=left, 0.5=middle, 1=right
of a given coordinate.
Era: Erase text box first before plotting text.
0 = Do not erase background.
1 = Erase background for the number of characters
found in the text.
n = Erase background for the n characters.
Angl: Angle of text, 0 is horizontal.
Col: Character color, for indices see color indices
above.
Not all text obey these attributes. For example labeling has its own justification and has no
erase option. Defaults are all determined by the program.

52 Chapter 5.
Defaults:
LABELATT=1.0, currentlinewidth, 2, 1, 0, 0.0, currentcolor
COMMATT*=1.0, currentlinewidth, 2, 1, 0, 0.0, currentcolor
TITLEATT=1.0, currentlinewidth, 2, 1, 0, 0.0, currentcolor
INFOATT= 0.5, 1, 2, 1, 0, 0.0, currentcolor
SUBATT= 0.6, currentlinewidth, 2, 1, 0, 0.0, currentcolor
GRIDSATT=0.5, currentlinewidth, 2, 1, 0, 0.0, currentcolor
* is a number from 1 to the number of comments in one (sub)plot
Extended ticks
The tick marks can be extended so that they are connected by curves following the current pro­
jection ( EXTEND=Y ). The number of points calculated in a curve is determined with LINESTEPS=
Default is 40 points, for a quick look you can do with less points, but for a quality plot 40 will
probably not be sufficient. The extensions of ticks in other sky systems is not yet implemented.
Drawing lines in plot
To add some free style plotting use PLLINE= The keyword is hidden but after specification it
will be asked unhidden in a loop that is aborted by PLLINE=!CR? The keyword accepts at
most 4 floating point numbers i.e. 2 coordinate pairs (in pixels or physical coordinates). The
action that follows is the plotting of a line between the two points. If the keyword appears again
and you specify only one coordinate the line is plotted from the previous last coordinate to the
specified coordinate. An application for these lines is the indication of zero levels for instance.
The line width, style and color are controlled by keywordPLATT= The range in width is [1..21],
the range in colors is 0..15] and line style is one from:
1 Full line
2 Long dashes
3 Dash­dot­dash­dot
4 Dotted
5 Dash­dot­dot­dot
Plotting ellipses
keywordELLPOS= is a position in grids or physical coordinates. If the keyword is not empty,
you start a loop in which a beam and angle is asked in ELLAXESPA= First value of this keyword
is the major axis, second the minor axis and the third is the angle in degrees wrt the positive
y axis. The units of the major and minor axes are in seconds of arc if both axes in the plot are
spatial axes, else, the units are grids. The appearance is controlled by ELLATT= and (see remarks
at PLATT=).

General GIPSY programs. 53
Using overlays
Overlays are made possible by asking in the current plot for a new (sub)set with INSET2=
The keyword is hidden so it must be specified beforehand. If no more overlays are needed use
INSET2=!CR? to abort the overlay loop. For each subset it is possible to create overlays. The
program calculates a box for the new (sub)set so that it is contained in the original box in
physical coordinates. With the prompted keyword BOX2= you can rearrange these values. Pixel
0,0 in the original set is transformed to physical coordinates which are converted to a pixel
position in the new set. From this point on all new pixels are scaled with new scales. A new
scale is calculated with:
OldGridSpacing
NewScale = OldScale * ­­­­­­­­­­­­­­
NewGridSpacing
There is no check on projection. You have to decide yourself whether the overlay makes sense or
you have to use the program REPROJ first. The keywords CONTOUR2=, COLIND2=, and GRAYSC2=
are described under CONTOUR= etc. If you select no original contours and gray scales in a mosaic,
but use INSET2= for a second (sub)set, it is possible to use different data origins in your mosaic
or use different contours per subset etc.
WARNING: If you want to use a grayscale map in your overlays, make sure that this is your
first (sub)set. Otherwise a grayscale map will obscure all previous plotted contours in a hardcopy.
examples using default files
1) Create contour plot of subset containing 'short observation beam' (data from A. Broeils).
Note the special use of the comment keyword.
linewidth=2
BEAMPOS=
BOX=­80 ­80 80 80
CONTOUR= ­0.1 ­0.05 ­0.025 0.025 0.05 0.1 0.2 0.4 0.8
GRAYSC=
GRDEVICE=x
GRID= n
INSET= app 1
SCALE=10 10
tick=360 360
nminor=1 1
markpos=
compos=10 51.8;­31 45;­10 29;­43 49;­70 65;
comment=``(2522);``(2522);fan beam;res. axis;(b)
commatt1=1 2 2 0.5 0 126;

54 Chapter 5.
commatt2=1 2 2 0.5 0 ­144;
commatt3=1.2 2 2 0 0 36;
commatt4=1.2 2 2 0 0 ­54;
commatt5=1.2 2 2 0 1;
xtitle=R.A. ­ offset (arcmin)
ytitle=Dec. ­ offset (arcmin)
titleatt=1.5 2
plline=­20 30 10 51.8; ­31 45 ­20 30;
platt=3;3
labelatt=1.3 2
plotinfo=n
The use of a Hersey symbol is demonstrated in: comment=n (2522); ....
2) Example of mosaic and use of recall files. There are five rows in the mosaic.
INSET=clean 1:29:2
BOX=­50 ­65 60 35
GRDEVICE=x
PLOTINFO=
MOSAIC=5
LINEWIDTH=1
PLSUB=y
SUBATT=0.8 1 2 0 1
DECIMALS=0
SUBPOS=
PERCENT=n
CONTOUR=­0.48 ­0.24 0.24 0.48 0.96 1.44
STYLE=
GRAYSC=
GRIDMARGIN=
labelmargin=25 9.1
SCALE=15 15
GRID=
MARKPOS=!opt2460;
MARKER=
TICK=60 360
NMINOR=1 1
XTITLE=R.A. (1950)
YTITLE=Dec. (1950)
AXMASK=
BEAMPOS=­48 ­63

General GIPSY programs. 55
BEAMATT=
BEAMNUM=2
COMMENT=
COMPOS=;
EXTENDTICKS=
LINESTEPS=
LABELATT=0.8 2
TITLEATT=1.0 2
The file 'opt2460.rcl' contains:
* 7 52 35.8 * 60 29 01
* 7 52 36 * 60 24 00
* 7 51 57.4 * 60 26 12
* 7 51 56.8 * 60 26 17
3) Example use of overlays. De primary set is called '30' and the overlay is the subset 'dtotal.new
1' (data: A. Szomoru).
axmask=
markpos=;
BEAMPOS=45 ­65
beampa=­98.50
beam=74.79 58.58
BOX= 30 ­75 100 ­25
BOX2= 30 ­35 50 ­22
CONTOUR2=0.005 0.01:0.06:0.01
contour=
GRAYSC=2 5:20:5
graysc2=
GRDEVICE=x
GRID=n
INSET=30
inset2=dtotal.new 1 ;
LINEWIDTH=3
MARKER=
PERCENT=
SCALE=3 3
STYLE=
titleatt=1.5,3
labelatt=1,3

56 Chapter 5.
xtitle=R.A. (1950)
ytitle=Dec. (1950)
xtpos=109.208405 10
titlemargin=20 20
markpos=;
compos=;
Plotting more overlays is achieved with more (sub)sets in INSET2=. For instance use '1005' as
primary data and 'warpleft 1' and 'warpright 1' as overlay subsets.
........
BOX= ­280 ­190 230 210
BOX2= 30 ­35 50 ­22;30 ­35 50 ­22;
CONTOUR=
contour2=0.002;0.002;
GRAYSC=6.69 17.49 43.94 110.4
graysc2=; ; ;
INSET=/dt1/arpad/bootes/1005
inset2=warpleft 1 ;warpright 1;
........
Note the use of semi colons in the file.
4) Example of using the color indices. The first 5 contours (in the dark regions of the gray scale
plot) are white and the remaining contours are black.
INSET=velo 1
BOX=­60 ­50 50 30
GRDEVICE=x
MOSAIC=
PLSUB=
DECIMALS=
SUBPOS=
PERCENT=n
LINEWIDTH=2
CONTOUR=3650:4100:50
COLIND=1::5 0
STYLE=
GRAYSC=3620:4100:10
graysc=
PLOTINFO=

General GIPSY programs. 57
GRIDMARGIN=
SCALE=5 5
GRID=
MARKPOS=!opt5533;
MARKER=
TICK=20 360
NMINOR=1 2
XTITLE=R.A. (1950)
YTITLE=Dec. (1950)
AXMASK=
xBEAMPOS=­55 ­45
BEAMPOS=­170 ­140
BEAMSHADE=
COMMENT=NGC 5533
COMPOS=­170 80;
TEXTATT=;1.3;1.5 2 2 0;1.5
INSET2=;
5) Example offset axis and the use of PLLINE= to draw offset axes in the plot. The contents
of the used recall files is displayed also.
AXMASK=
BEAMPOS=
BOX= ­30 14 30 40
CONTOUR= ­1 ­0.5 0.5:2:0.5
GRAYSC=
GRDEVICE= x
GRID=n
INSET= 19slice dec 0
LINEWIDTH=3
gridmargin=0 0
PERCENT=
SCALE=
STYLE=
box=­30 14 30 40
markpos=!xvrot
marker=17;
titleatt=1.5,3
labelatt=1,3
markpos=;
compos=!compos
commatt1=2,3,1,0.5,0,0,1

58 Chapter 5.
commatt2=2,3,1,0.5,0,0,1
comment=!comment
xtitle=Offset along major axis (arcsec)
ytitle=Heliocentric velocity (km/s)
titlemargin=20 20
plline=!plline
platt=!platt
Contents of the used recall files:
xvrot.rcl: (positions of markers)
­11.3636 33.74362
­10.2272 33.68168
­9.09090 33.58433
­7.95454 33.47814
­6.81818 33.31
.....
11.36363 22.98256
;
compos.rcl: (positions of comments)
­4.59 14
4.59 14
;
comment.rcl: (Hersey symbols as comments)
``(2262)
``(2262)
plline.rcl: (physical­ and grid coordinates are mixed)
0 14 0 40
u 229.286 u 14234.2 u 229.248 u 14234.2
14 17 18.5455 17
16.273 16 16.273 18
platt.rcl: (attributes for the lines, width, style, color,
two lines in long dashes, two lines in full)
1,2,1
1,2,1
3,1,1

General GIPSY programs. 59
3,1,1
5.6 Printing data
PRINT
The program PRINT writes pixel values on the screen or prints them.
PRINT first selects an input set (and subset(s)) and a frame, with the keywords INSET= and
BOX=. Then, the program requests that you assign an output format to the keyword FORMAT=.
The formats available are floating, exponential, and integer format. To specify a floating format,
give a format string beginning with any character except an E, e.g.,
FORMAT=FFFF.FF
resulting, for the sample value 3453.32456, in 3453.32. To assign an integer format, use the same
format but without a dot, e.g.,
FORMAT=TTTT
resulting, for the same value, in 3453. To specify an exponential format, type a format string
with an E as first character, for example,
FORMAT=EEEE.E
resulting, for the same value, in 3.5E+03. If a carriage return is given as input to FORMAT=, then
PRINT selects the format best fitting the absolute values of the minimum and maximum found
in the header; in absence of this header information, the program selects the exponential format.
The default number of columns the data are written in is 80. To specify another number, use
the hidden keyword TWIDTH=. For example,
PRINT TWIDTH=120
The default output device is the screen. To select another output device, use the hidden keyword
PRINT=, described under DISK.
5.7 Statistics
STAT
The program STAT calculates and plots elementary statistics in frames.
First, supply an input set (and subset(s)) to INSET=. Then, one or more frames can be defined
for the specified subset(s), with the keywords BOX01= up to BOX10=. To specify the entire subset
as the only frame, answer BOX01= with a carriage return. Entering a carriage return to a next
prompting with BOX*= (* ranging from 02 to 10) stops the input of frames.
Next, STAT prints in the Common Output Area per specified frame the results of the calculations.
These results are given for each subset in particular and for all subsets together. For a sample
set part of the output can be:
subnr pixels sum mean rms min max blanks
=============================================================================
1 57447 3.01 5.245E­05 .263 ­.628 1.67 153
=============================================================================

60 Chapter 5.
Furthermore, select a graphics device to plot on, with GRDEVICE=. Finally, assign plot options
to the keyword PLOT=. The program repeats prompting with this keyword until an X is entered.
For a list of available options, give a carriage return. The plot shows the calculations for all
frames and subsets. For example,
PLOT=SUM PLOT=MEAN PLOT=X
HISTOG
The program HISTOG calculates some statistics and creates a histogram of values for (sub)sets.
First, specify the data, with INSET= and BOX=. Then, the keyword RANGE= can be used to in­ or
exclude a range of pixel values from the calculations. Next, HISTOG requests a graphics device
to plot on, with GRDEVICE=.
If the specified data span more than one subset, a plot mode has to be specified, with AUTOSCALE=.
In the default mode (AUTOSCALE= !CR?), the program itself scales the plot for each subset. In
the other mode ( AUTOSCALE=NO ), all plots are scaled as the first one.
To determine the range of values along the X­axis of the histogram, HISTOG needs the minimum
and maximum data values. If they are not present in the set header, the program prompts for
them, with the keyword MINMAX=. For example,
MINMAX=\Gamma4.8701 14.857
Next, the keyword FIXBIN= allows one to choose how the bin width of histograms has to be
specified, by giving the bin width itself ( FIXBIN=YES ) or by giving the number of bins (
FIXBIN=!CR? ). HISTOG prompts for the bin width with BINWIDTH=. E.g.,
BINWIDTH=10
HISTOG prompts for the number of bins with BINS=. The default is 100.
Subsequently, some statistics are displayed for the specified subset(s), in the Common Output
Area of the Hermes Window. Furthermore, the Y­axis interval, that is, the range of counts, can
be entered with COUNTS=. As a default, the entire range is selected. For example,
COUNTS=5 20
To include a Gaussian curve in the plot(s), see the document HISTOG.DC1.
5.8 Manipulating sets
COPY
The program COPY copies (sub)sets, with the option to change subset sizes.
The keyword INSET= prompts for specifying the input (sub)set(s). Next, a frame can be selected
for the input subset(s) to define the output subset(s), with BOX=. BOX= allows for entering a

General GIPSY programs. 61
frame greater in size than the input subset(s). Then, in the output set, the values of the pixels
that cannot be copied from the input set are set to blank.
Furthermore, an output set has to be assigned to OUTSET=.
SCALE
The program SCALE scales the data in subsets by a factor A and an offset B. The output subsets
have the format A \Theta input subset + B.
The first three keywords SCALE prompts with are INSET=, BOX=, and OUTSET=. OUTSET= has as
a default the input set name.
To specify the scaling factor A and the offset B, SCALE prompts with AB=. For example, to
assign the value 3.5 to the scaling factor and 2 to the offset, the input
AB=3.5 2
has to be given. The default values of A and B are, respectively, 1 and 0.
CLIP
The program CLIP has two options:
1. CLIP transfers values of an input set to an output set if they lie within a preset range,
setting to blank values outside that range.
2. CLIP blanks values of an input set in an output set if they lie within a preset range,
transferring to the output set without change the values outside that range.
First, the program requests that you give values to INSET=, BOX=, and SETOUT=, to specify,
respectively, the input set (and subsets), a frame for the subsets, and an output set.
The keyword RANGE= is used to specify the range of values. To specify the preferred program
option, choose one of the following input formats.
1. A range of values x ! value ! y to be transferred has the input format:
RANGE=x y.
2. A range of values x ! value ! y to be blanked has the input format:
RANGE=y x.
For example, RANGE=2 5 results in a transfer of all values falling within the range 2 ! value !
5 (and a blanking of all other values), and RANGE= 8 3 results in setting blank the values falling
within the range 3 ! value ! 8 (and transferring all other values).
To specify a range, the values INF and \GammaINF, representing the minimum and maximum values
of the system, also can be used. For example,
RANGE=\GammaINF, 4
results in a transfer of all values smaller than 4.

62 Chapter 5.
CONDIT
The program CONDIT provides, like CLIP, a conditional transfer of values from an input set to
an output set. Here, the condition (set by RANGE=) applies to the values of another input set,
the so­called ``test set''.
Consider the following example. A radio astronomer has a series of images with varying frequency
of a particular sky area. Only one of them shows clearly a number of sources, having values above
50 mJy. CONDIT can be used to identify these sources in the other images as well: pixel values
of the input set are transferred to the output set if their corresponding values in the test set are
higher than 50 mJy.
The program requests that you specify an input set (INSET=), a frame for the subsets (BOX=), a
test set (SETX=), and an output set (OUTSET=). Then, the transfer condition has to be specified,
by assigning a range of values to RANGE=. For the above example, the appropriate range is
RANGE=50 INF
passing values corresponding with test values higher than 50, while blanking all the other values.
EDITSET
The program EDITSET edits data in a set on pixel­by­pixel basis.
The program requests a set (and subsets), with INSET=. Furthermore, a frame can be specified,
with BOX=.
To change the specified data, either an expression can be assigned to the keyword EXPRESSION=
or, skipping this keyword by giving a carriage return, one or more values can be entered with
NEWVAL=.
If you choose to specify an expression, use as parameters axis names (RA, DEC, etc.) and DATA,
meaning the old data value. Furthermore, see the document EDITSET.DC1 for a list of all
mathematical functions, constants, and operations allowed. For example,
EXPRESSION=DATA*ABS(RA)
meaning that the selected pixels are to be multiplied by the absolute value of their RA grid
position.
Choosing the ``manual mode'', give input to NEWVAL= for the pixel position displayed on the
screen in a message of the format:
New value at (x1,...,xn): [old value]
For example,
New value at (1,5,2): [0]
If two or more pixels were selected, then the program repeats prompting with NEWVAL=. Giving
a series of input values prevents repeated prompting. For example,
NEWVAL=1::4
assigns the value 1 to the displayed pixel as well as to the next three pixels that were selected.
DECIM
The program DECIM decimates a set along one or more axes by (an) integer factor(s). DECIM
first selects an input set (and subset(s)) and a frame, with INSET= and BOX=.

General GIPSY programs. 63
Subsequently, a decimation factor can be entered for each axis, to the keyword DECIM=. As input,
only integers are accepted. If subsets with the axes RA, DEC, and FREQ were specified, then
DECIM= can be answered with, e.g.,
DECIM=2 1 3
decimating the RA axis by the factor 2 and the FREQ axis by the factor 3. On a decimated
axis, the value zero always is retained. If, for example, the RA axis ranged from \Gamma8 to 7, then
the decimated RA axis has the positions \Gamma8, \Gamma6, \Gamma4, \Gamma2, 0, 2, 4, and 6 of the original axis.
Furthermore, DECIM asks for an output set, with OUTSET=.
CBLANK
The program CBLANK changes a certain value into BLANK and/or changes a BLANK into a
certain value. First, CBLANK requests to specify the input (sub)set(s), with INSET=. Then, the
keyword BLANK= asks for a value to be blanked. As a default, BLANK itself is selected.
Subsequently, the keyword VALUE= selects a value to replace BLANK. The default value is again
BLANK.
5.9 Combining sets
ADD, SUB, MUL, and DIV
The programs ADD, SUB, MUL, and DIV perform the respective arithmetic operations of addi­
tion, subtraction, multiplication, and division. They can be used either to combine a series of
subsets (or frames) with a single subset (or frame) or to pairwise combine two series of subsets
(or frames).
The first option results in a series of calculations in which the first operand has changing values
and the second operand remains the same in value. The chosen program requests the first
operand, a series of subsets, with INSET= and BOX=, and the second operand, one subset, with
SETX=. The last keyword is OUTSET=.
The second operation results in a series of calculations in which the first operand is the nth
subset of the first input set and the second operand is the nth subset of the second input set.
For example, in the program SUB, specifying
INSET=SAMPSET1 FREQ 1:15 BOX=!CR? SETX=AURORA FREQ 1:15 OUTSET=SAMPSET2
results in subtracting the first subset of the second input set, AURORA, from the first subset
of the first input set, SAMPSET1, that is
(SAMPSET1 FREQ 1) \Gamma (AURORA FREQ 1)
followed by
(SAMPSET1 FREQ 2) \Gamma (AURORA FREQ 2)
(SAMPSET1 FREQ 3) \Gamma (AURORA FREQ 3)
etc.

64 Chapter 5.
MEAN
MEAN calculates the mean of a number of subsets in a set.
First, similar as to SUM, the input set and the axis along which to average pixels have to be
assigned with the keyword INSET=. Subsequently, the keyword BOX= can be used to define the
frame over which the input subsets have to be averaged.
To specify weights for individual subsets, WEIGHT= can be used. By default, equal weights are
assigned.
Finally, MEAN requests that you give a value to OUTSET=.
SUM
The program SUM sums a number of subsets of a set.
First, SUM asks, with the keyword INSET=, for the input set and the axis along which pixels
have to be integrated. E.g., if the set AURORA has three axes:
RA­NCP from \Gamma7 to 8
DEC­NCP from \Gamma7 to 8
FREQ­OHEL from 1 to 59
and DEC is the axis along which pixels must be summed, then the input has to be
INSET=AURORA DEC
With the following keyword, BOX=, SUM requests the frame over which the input subsets have
to be added.
Subsequently, with the keyword CUT=, cutoff levels can be set, a lower and an upper cutoff level.
Data values not between these levels are ignored in the sum.
The last keyword is OUTSET=, asking for the set where the results must be stored.
COMBIN
The program COMBIN can be used to perform several mathematical operations for more general
purposes upon sets.
First, a mathematical expression is requested, with the keyword RESULT01=. In this expression,
input sets have to be represented by a symbol with the format $n, where 1 Ÿ n Ÿ 32. COMBIN
later asks for the full specifications of these parameters. For example, to specify an expression
that adds two input sets, type
RESULT01=$1 + $2
or, to specify an expression that adds gaussian noise to an input set, with a mean of zero and
an rms of two, give
RESULT01=$1 + RANG(0, 2)
The last example contained the function RANG. For a list of all mathematical functions, con­
stants, and operators allowed, see the document COMBIN.DC1.
With the keywords RESULT02=, RESULT03=, etc., COMBIN allows for specifying more mathe­
matical expressions, up to 32. A carriage return stops COMBIN asking for more expressions.
Subsequently, COMBIN requests that you fully specify the respective input sets, subsets, and

General GIPSY programs. 65
frames, with the keywords SET01=, BOX01=, SET02=, BOX02=, etc. All input sets must have
the same number of subsets. The output set(s) get(s) the same size as the first input set.
5.10 Saving sets
WFITS
The program WFITS transfers data on disk to magnetic tape or disk, in FITS format.
First, WFITS selects the data to transfer, with the keyword INSET=.
Pixel values are transferred as integers of 8, 16, or 32 bits. The program prompts for the number
of bits with the keyword BITPIX=. The given number determines the range of integer values,
preferably matching the range of input data values, as well as the size of the output file, preferably
taking up no more space than necessary. Input data outside the specified range are represented
by the lowest value in that range. For antenna patterns, 32 bits is advised. The default number
is 16.
WFITS searches for the minimum and maximum values of the input data in their header. If it
cannot find these values, it prompts with the keywords DATAMIN= and DATAMAX=. For example,
DATAMIN=\Gamma3.6 DATAMAX=17.2
Finally, an output device has to be assigned to TAPE=. For a list of available devices, give a
carriage return. To write the data to a subdirectory on disk, enter the name of the subdirectory.

Chapter 6
Reducing radio data
6.1 Introduction
6.2 General radio applications
ffl CLEANing
ffl SMOOTHing
ffl (HI) profiles
ffl PBCORR
ffl Converting mJy to Kelvin
6.3 WSRT specific applications
still to come
6.4 VLA specific applications
still to come
66

Chapter 7
IRAS reduction
7.1 Introduction
This chapter describes IR­GIPSY, the GIPSY software for the reduction of data obtained from
the Infrared Astronomical Satellite (IRAS). It is intended as an introduction for the novice IR­
GIPSY user. For more general information on GIPSY, see chapter 5. Section 7.2 introduces the
IRAS instrument 1 . Section 7.3 describes the data base for IRAS data. Section 7.4 presents the
software for these data.
7.2 IRAS
7.2.1 Instrument and mission
The Infrared Astronomical Satellite (IRAS) surveyed about 95 % of the sky, in four broad spec­
tral bands centred on 12, 25, 60 and 100 ¯m, during a ten month period in 1983. A low­resolution
spectrum of the bright sources was obtained as well, with the Low­Resolution Spectrometer
(LRS). Precession at a rate of about 1 o per day, kept the orbit of the spacecraft remaining
perpendicular to the earth­sun vector (Figure 7.1). The spacecraft attitude control system per­
mitted the instrument to scan in ecliptic longitude along small circles at constant elongation 2
between 60 o and 120 o . Most survey scans, however, were taken within 6 o of the quadrature.
For each spectral band there were two detector arrays. The arrays were arranged such that the
second one scanned the same area of sky some 5 to 10 seconds later than the first one.
A semi­overlapping scan strategy was used for the ``all­sky'' survey. Redundant coverage on the
time scale of hours was provided by advancing the instrument in elongation by half of the width
of the focal plane on a subsequent scan, usually the next orbit. A complete survey conducted in
this fashion is designated as an HCON (Hours Confirmation), and locally consists of (almost)
parallel scans which overlap.
Roughly 70 % of the sky was surveyed three times in such a manner, 25 % was covered twice,
and about 5 % was missed. Thus most regions near the ecliptic plane were observed 12 times,
1 For more information, see Infrared Astronomical satellite (IRAS) catalogs and atlases, volume 1 of Explanatory
Supplement, NASA reference publication 1190, Washington, DC, 1988.
2 Here, elongation designates the angle between the telescope axis and the IRAS­Sun vector.
67

68 Chapter 7.
Figure 7.1: A schematic drawing of the orbital geometry. The orbital altitude, 900 km, and
inclination 99 ffi , combined with the earth equatorial bulge lead to a precession of the plane of
the orbit about 1 ffi per day. As a result, the orbit normal always pointed towards the Sun as
the satellite orbited above the Earth's terminator. By pointing the satellite radially away from
the Earth, the cold telescope was shielded from the heat loads from the Sun and Earth while
providing natural scanning motion across the entire sky in about six months. A sequence of
hours­confirming scans on the celestial sphere is also shown. A celestial object does not change
its position on the sky, during the passage over the IRAS focal plane and is seconds (see figure
3.2) and hours confirmed.

IRAS reduction. 69
Figure 7.2: IRAS focal plane. Of the 62 infrared detectors the three filled­in were inoperative; the
cross­hatched detectors showed a higher noise level. The normal scan direction of objects farther
away than a few 100,000 km is shown. Detectors at the four wavelength bands are ordered in
two arrays per band, allowing confirmation of the detection of a source within 5 to 10 seconds.

70 Chapter 7.
on time scales of seconds, hours, and months. The overlap of the scans increases toward the
ecliptic poles. Scans from different HCONs over the same area usually intersect at an angle due
to precession of the satellite orbit. Therefore, even small areas of the sky can be very unevenly
covered. The layout of the focal plane (see Figure 7.2) and the data processing for the initial
IRAS product, the IRAS Point Source Catalog (PSC), was optimized for detecting discrete
unresolved celestial sources.
Each of the 59 active IRAS detectors has a different response function. Most detectors have
rectangular apertures of 0.75 to 3 (in the in­scan direction) and 4.5 to 5 arc minutes (in the cross­
scan direction). Consequently, the spatial resolution is different in the two directions, significantly
worse in the cross­scan direction.
The scanning speed of IRAS was 3.85 arc minutes/sec. Thus the in­scan length of 0.75 arc
minutes of a 12 or 25 ¯m detector was traversed in 0.2 seconds. That is, in just 3 data samples
a point source is visible. All astronomical objects, including solar system objects, exhibit the
same timing at an instantaneous crossing. Solar system objects, however, will in general not be
hours­confirmed.
During all survey observations, LRS observed as well. The LRS was basically an objective prism
spectograph, oriented in such a way that the dispersion was aligned with the scan direction.
Therefore, it measured useful spectra of relatively isolated point sources only. Two overlapping
wavelength bands were scanned simultaneously, one ranging from 7.7 to 13.4 ¯m and the other
from 11.0 to 22.6 ¯m. In both bands, the resolution increased from 20 at the short­wavelength
to 60 at the long­wavelength side. The integration time per resolution element was 60 ms, which
resulted in noise levels equivalent to 1.5 Jy at the shorter and 3 Jy at the longer wavelengths.
The LRS aperture mask in the focal plane measured 6 arcmin in­scan by 15 arcmin cross­scan
(see figure 7.2). This wide field of view ensured a sky coverage identical to that of the IRAS
survey: 96 percent of the sky was observed at least twice and 72 percent three times. To reduce
spatial confusion, the aperture width was covered by three detectors at the short wavelengths
and by two at the long wavelenghts. The detectors were sampled continuously, and the data
were received on the ground together with the data from the survey array.
7.2.2 IRAS data products
IR Data products available in GIPSY:
ffl Survey band 1, 2, 3, 4, LRS
ffl AO band 1, 2, 3, 4, LRS
ffl Spline band 1, 2, 3, 4
7.2.3 Pointing reconstruction
7.2.4 Timing
IRAS timing is done in so­called satcal ticks. A satcal tick is not quite equal to a second (actually
1 tick ¸1.00005 seconds). The satcal tick time units are used everywhere in IR­GIPSY, unless
explicitly stated otherwise. Satcals and satcal ticks are interchangeable.

IRAS reduction. 71
1/8 tick
oe ­
electronic delay
and read out time
oe ­
N N N N N N N N
@
@
@I
sample
oe n­1 ­
n+1
\Omega \Omega \Delta \Delta \Delta \Delta \Delta \Delta
oe 0.5 tick ­ 6
BPHF
oe 1 tick ­
6
SATCAL n
6
SATCAL n+1
Figure 7.3: What happens in a satcal tick
Within one satcal tick a number of samples (from 1 for splines up to 32 for LRS data) are taken.
The timing parameters of the samples and Boresight Pointing History File (BPHF) with respect
to satcals are indicated in figure 7.3 (for 60¯ data with 8 samples per satcal). As shown in the
picture, the BPHF is valid for the time mid between two satcal ticks. Furthermore, the samples
are offset with respect to the satcal due to the read out time (different for each detector) and
the electronic delay (different for every band). Note that this offset can be negative. IR­GIPSY
programs account, if timing is at importance, for these different effects.
7.3 IRAS data in GIPSY: IRDS
7.3.1 Introduction
This section describes the database for raw IRAS data, the InfraRed Data Structure (IRDS).
Raw IRAS data represent the data as they are sent down from IRAS to a ground station: a
series of digitized voltages corresponding to sky brightness as a function of time. By defining a
particular on­sky area and extracting from the database the raw data of a certain band associated
with that area, a so­called ``custom plate'' is created. The part of a scan falling within a custom
plate is called a snip. So, a custom plate corresponds to a collection of snips in a single band.
See figure 7.4 for a sample custom plate. Subsection 7.3.2 discusses how raw data are ordered in
IRAS data sets. Subsection 7.3.3 deals with the header information in such data sets.

72 Chapter 7.
+
RA1 RA2
RAc
DEC1
DEC2
DECc
B B
B
B
B
B
B
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B B
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\Theta
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\Theta \Theta
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\Theta \Theta
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\Theta
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\Theta
\Theta \Theta
B
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oe snip
oe scan
Figure 7.4: Sample Custom Plate with CENTER = (RAc,DECc) and SIZE = (RA1\GammaRA2)
(DEC1\GammaDEC2).
7.3.2 Data structure description
Raw IRAS data in GIPSY are stored as four­dimensional data sets. Going from fastest to slowest
axis, in an IRSD the raw IRAS data are ordered as follows:
1. samples (per satcal tick) (SAMPLE axis)
2. satcal ticks (TICK axis)
3. sequential detector number (SDET axis)
4. snip number (SNIP axis)

IRAS reduction. 73
'' '' '' '' '' '' '' ''
'' '' '' '' '' '' '' ''
'' '' '' '' '' '' '' ''
'' ''
'' ''
'' ''
'' ''
­
satcal tick
?
sample per
satcal tick
j j j3
detector
number
'' '' '' '' '' '' '' ''
'' '' '' '' '' '' '' ''
'' ''
'' ''
'' ''
'' ''
SNIP header:
­SNIP params.
­intended pos.
H H H H H Hj'' ''
'' ''
TICK­SNIP
­BPHF pointing data
­etc.
­etc.
\Phi \Phi \Phi*
SDET­SNIP
­focal plane pos.
­read out time.
­cal. factors.
'
'
'
'
'7
Figure 7.5: GIPSY implementation of a single snip
etc.
SNIP nr. ­
1 2 3 4 5 6 7
@
@I
SNIP, see
figure 7.5
TOP header:
­cube params.
­IRAS params.
­nr. of SNIPs.
@
@
@R
Figure 7.6: GIPSY implementation of an IRAS Data Structure (IRDS)

74 Chapter 7.
Figure 7.5 shows the way an individual snip (the part of a scan which falls within a custom
plate) is put into a three­dimensional data structure. Figure 7.6 shows a complete IRAS Data
Structure (IRDS) consisting of a series of snips from different scans. Since snips are collected by,
e.g., SNIPping parts of scans that run through a given custom plate (see section 7.4.2, program
PLATE), in general different snips have different lengths. As a result, the shorter snips in an
IRDS have to be padded with undefined values(see figure 7.6). Using this padding scheme, in
the worst case 50% of a given IRDS will be empty.
Different ``instruments'' (for example, LRS, Survey band 1, Survey band 2, etc., Spline band 1,
etc.) are all treated as different bands. Different bands are put into different data sets.
7.3.3 IRDS headers
Part of the header information must be present to allow programs to work on the data. The
program PLATE automatically creates these headers. Examples of header items at top level are
NAXIS, giving the number of axes in the data set, INSTRUME, specifying the instrument/band,
and SKYSYS, specifying the coordinate system of the snip area. At the SDET level, at least
DETECTOR, giving the detector number, must be present. Some of the obligatory headers at the
snip level are SNIPCAL, giving the satcal ticks since the beginning of the snip, and SNIPDUR,
giving the length of the snip in satcal ticks.
For more detailed information about IRDS, see the IR­GIPSY Programmer's Manual.
7.4 IRAS reduction programs
7.4.1 Introduction
This section describes how to use the GIPSY software for reduction of IRAS data. Subsec­
tion 7.4.2 deals with programs that create IRAS data structures, PLATE and RDBPHF. Sub­
section 7.4.3 presents some programs that can be used to display raw IRAS data, TRACKS,
PLSCAN, and VIEW. Subsection 7.4.4 concerns a program for intensity calibration of the raw
survey data in these structures, ZODYCAL. Subsection 7.4.5 discusses a program that creates
survey maps, ***. Subsection 7.4.6 presents a program that calibrates LRS data, LRSCAL. More
details about the discussed programs can be found in the relevant .DC1 documents.
7.4.2 Getting IRAS data into GIPSY
This subsection describes two programs to get IRAS data into GIPSY, PLATE and RDBPHF
PLATE
The program PLATE builds an IRAS Data Structure for a particular area on the sky. All IRAS
data pertaining to such an area is called a ``custom plate'' (see figure 7.4). The layout of a custom
plate is defined by specifying values for the keywords CENTER=, SIZE=, and COOR=.
To start the program, give
PLATE

IRAS reduction. 75
The program asks then to identify the instrument, with INSTRUME=. The identification consists
of observation mode and band name. Observation modes are SURVEY, AO, SPLINE, etc. Band
names are 12, 25, 60, 100, LRS, etc. The band names 12, 25, etc., indicate a 12 ¯m band, a 25
¯m band, etc. For example,
INSTRUME=SURVEY 25
to read 25¯ survey data.
PLATE prompts then with the keyword CENTER=. The center of the custom plate must be entered
here. Some examples of values are
CENTER=3h25m28s ­18d16m3s
and
CENTER=46.6 ­18.2
The next keyword is SIZE=. The default custom plate sizes are 1.0 by 1.0 degrees. For example,
SIZE=1.5 2.8
results in a custom plate measuring 1.5 degrees in longitude and 2.8 degrees in latitude.
With the keyword COOR=, PLATE requests the standard coordinate system. The default coordi­
nate system is EQUATORIAL 2000.0. A sample input value is
COOR=GALACTIC
With the following keyword, IRSET=, PLATE asks to give the name of the set to which the data
have to be written. For example,
IRSET=B­THREE
where B­THREE is an arbitrary set name.
The last two keywords, OBJECT= (for example, OBJECT=CAS A ) and OBSERVER= (for example,
OBSERVER= YTSMA ), add the names of object and observer to the custom plate. A carriage
return leaves these names in the IRDS blank 3 .
RDBPHF
The program PLATE adds the intended positions as found on the input optical disk into the
header of the IRDS. This results in a positional accuracy of ¸10 arcminutes.
Better position accuracy is obtained when the Boresight Pointing History File 4 (BPHF) data
are used. The IRAS program RDBPHF adds BPHF information to the header of the IRDS.
After starting up this program (to start a program, just type the program name), RDBPHF
requests the name of the input IRDS, with the keyword IRSET=. For example,
3 More sensible default values will be inserted later.
4 In GIPSY the latest version of the BPHF is being used which is sometimes called the Super BPHF

76 Chapter 7.
IRSET=B­THREE
where B­THREE is the name of a set created with PLATE.
7.4.3 Inspecting raw IRAS data
This subsection explains three programs to inspect raw IRAS data: TRACKS, PLSCAN, and
VIEW.
TRACKS
The program TRACKS plots IRAS tracks.
First, TRACKS asks for an input set, with the keyword IRSET=. Then, the keyword SIZE=
prompts for the size of the plot, in longitude and latitude. The plot has the same centre as the
specified set. The default size equals to the size of the input set. For example,
SIZE=2.5
Next, enter the snips to plot, to SNIP=. As a default, all snips are plotted.
Subsequently, give the sequential detector numbers to plot, to SDETS=. By default, all sequential
detector numbers are plotted.
Furthermore, the program requests an output device, with GRDEVICE=. To obtain a list of the
available devices, give a carriage return. The list looks like
NULL TEKTRONIX L1LASER P1LASER
where NULL means ``no plot'', TEKTRONIX indicates the screen, and both P1LASER and L1LASER
are devices for hardcopies.
Finally, the keyword POS= allows for specifying positions to be plotted. In the plot, they appear
as plusses. As a default, no positions are plotted.
PLSCAN
The program PLSCAN plots raw IRAS scans. This program can plot the data as function of the
in­scan distance to a reference position, to assign to the next keyword, POS=. Such a position
has to lie within the coordinates defined in the set header. As a default, PLSCAN plots the data
as function of the satcal ticks.
PLSCAN first asks to specify an input set, with IRSET=. Next, the program requests that you
specify the sequential detector numbers to be plotted, with SDET=. Give the first and the last of
the series of numbers. As a default, all detectors are plotted.
The keyword SORT= asks if the specified detectors have to be plotted according to the layout of
the focal plane. The default value is YES.
PLSCAN allows for plotting the detectors aligned in the time domain. Then, enter a carriage
return to ALIGN=.
The keyword TICKS= prompts for the part of the snip to be plotted. Here, the first and last
satcal tick of that part can be typed. A carriage return selects the entire snip.
Finally, PLSCAN requests the graphics device to plot on, with GRDEVICE=.

IRAS reduction. 77
VIEW
Still to come: use of VIEW for IRAS
7.4.4 Calibration of survey data
The calibration program ZODYCAL calibrates the raw data of an IRAS data structure created by
PLATE and possibly --although not necessarily-- enriched with BPHF information by RDBPHF.
First, ZODYCAL requests the name of the set it has to calibrate, with the keyword IRSETIN=.
Then, the program asks to specify the name of the output set, with the keyword IRSETOUT=.
The default is the name of the input set.
With the next keyword, ZODY=, the program asks if the zodiacal emission model has to be
subtracted. The default is YES.
The last keyword, UNITS=, prompts to specify the units of the output set. The default units are
MJy/sr. Other input can be, for example,
UNITS=Jy
7.4.5 Map making
still to come
7.4.6 Calibration of LRS data
The program LRSCAL generates calibrated LRS spectra from an IRDS.
The input data set is requested with the keyword IRSET=. This data set must contain LRS data.
Otherwise, LRSCAL generates an error message and returns with IRSET=. Then, the position at
which one or more spectra must be generated has to be specified, with the keyword POS=. The
default position is the center of the custom plate (see subsection 7.4.2, program PLATE, keyword
CENTER=). Subsequently, LRSCAL displays the snip numbers of the spectra in the data set that
correspond to the positions specified with POS= on the screen.
With the keyword IRSETOUT=, the program prompts for the name of the output IRDS. As a
default, no output set is generated.
The keyword SNIP= allows you to specify the snip number(s) of the spectrum or spectra to be
generated. The program allows for repeated input to this keyword.
The first appearance of SNIP= has by default value all snip numbers in the data set. Other input
can be, for example,
SNIP=1
or
SNIP=1:4
where 1:4 implies snips 1, 2, 3, and 4.
LRSCAL then prompts again with SNIP=. Giving a carriage return results now in calibration of
all remaining spectra. If all spectra in the set have to be calibrated, then give
SNIP=ALL

78 Chapter 7.
LRSCAL generates, in addition to a specified series of spectra, an average spectrum of that series.
So, entering
SNIP=1:4 SNIP=5:7
differs, with respect to the generated average spectra, from entering
SNIP=1:3 SNIP=4:7
To stop LRSCAL from prompting with SNIP=, give
SNIP=QUIT
The program prompts then again with the keyword POS=. A carriage return causes LRSCAL to
use the same positions as entered previously. The program stops by giving
POS=QUIT
After the first time SNIP= is asked, the program prompts with the keywords UNITS= and
GRDEVICE=. With UNITS=, the units of the data after calibration are requested. The default
value is Jy (Jansky). With GRDEVICE=, the program requests a graphics device for display of the
generated spectra.

Chapter 8
Advanced use of GIPSY
8.1 Recall files
Keyword values can be extracted from default or recall files. The ``recall file'' serves as input
to the keyword. It must be a text file with a name like ``name.rcl''. Every line in this file is a
separate input and either the whole file or a part of it can be specified (See chapter 4).
Example: In CPLOT it is possible to mark positions. The coordinates of these positions can be
given manually at the MARKPOS= prompt or with a recall file. A recall file 'positions.def ' contains
for example:
* 3 13 33.51 * 41 16 34.2
* 3 13 55.67 * 41 15 9.5
* 3 13 59.41 * 41 12 9.3
* 3 13 59.74 * 41 14 19.1
* 3 14 3 * 41 8 50
If you want to plot positions 2, 3 and 4, use: MARKPOS=!positions 2:4
8.2 Default files
Another way to pre­specify keywords for a task, is the use of a ``default file'' containing keywords
specifications. Default files have the format ``name.def''. At present only the current working
directory is searched for default files. Only one keyword specification per line is allowed. Example:
The default file 'myplot.def ' is used to control CPLOT and contains:
inset=velo2 2
BOX=­48 ­30 35 10
CALCMNMX=Y
PERCENT=
CONTOUR=­10 ­5 5 10 140:250:10
MARKPOS=!positions 2:4
MARKER=
GRAYSC=150 160 170 180
79

80 Chapter 8.
MOSAIC=3
SCALE=20 40
GRIDS=y
STYLE=N
BEAMPOS=20 ­20
line=1
tick=19 10*6
nminor=3 3
xlabel= R.A. (1950.0)
ylabel= Dec. (1950.0)
xtitle= R.A. (1950.0)
ytitle= Dec. (1950.0)
deltashade=0.5
grdevice=x
In tHermes CPLOT using this default file is started with: myplot(CPLOT). Keyword values spec­
ified in the UCA are taken into account first. Keywords that are not prespecified, are prompted
by CPLOT.
8.3 GIPSY in batch mode
GIPSY can be used in a non interactive way. For this there is a special Hermes version called
nHermes. The syntax for nHermes is explained in chapter 4.
ffl Example:
nhermes \GammalMylog ''FLUX, INSET=cg1517 v ''
Let 'nhermes' start task FLUX on all subsets of set cg1517 and put results in file My­
log.LOG.
8.4 COLA FILES
8.4.1 Introduction
COLA is a small (but powerful) high­level control language for use with Hermes (in tHermes
type run COLA, with nHermes, a COLA file is one of the parameters). Using COLA you can write
a program to execute a sequence of commands. A COLA script file must have the extention .col
In such a COLA file you can use a number of facilities, like:
­ variables (and substitution of their values in commands)
­ a conditional statement (IF)
­ repetitive statements (FOR, WHILE, REPEAT)
­ input/output with Hermes console (READ, WRITE)

Advanced use of GIPSY. 81
COLA compiles a source program to some intermediate code, and, if no errors are detected,
starts to execute that code. If an error is found, the line containing the error is printed, together
with an explanation and compilation is stopped. To introduce the general form and appearance,
an example COLA program is presented, which shows a couple of maps on your monitor, prints
them, and copies them to another set.
! example COLA program
! date: 15 Jul 1985
integer i ! loop counter
integer nsubs ! number of subsets
nsubs = 32 ! default number
READ ''Subset numbers [%nsubs] ?'' nsubs ! prompt user
FOR i = 1 , nsubs ! for all subsets...
WRITE ''Processing subset %i'' ! give message
''VIEW,INSET=NGC4214 %i,CLIP='' ! display
''PRINT,INSET=NGC4214 %i,BOX=,FORMAT='' ! print
IF i != 10 THEN
''COPY,INSET=NGC4214 %i,OUTSET=OUT1 %i'' ! first 10 to OUT1
ELSE
''COPY,INSET=NGC4214 %i,OUTSET=OUT2 %i'' ! others to OUT2
CIF
CFOR
This example shows some aspects of COLA, all of which will be discussed in detail further on.
But a few points can be made immediately:
­ COLA makes no distinction between upper and lower case letters
­ layout doesn't affect the meaning of a program
­ comments can be added (the rest of a line, following ! is skipped, except when the
! occurs in a string)
8.4.2 Cola syntax
Constants
COLA knows 4 datatypes:
integer 1, 0, ­12, etc.
real 3.14, ­.01, etc.
logical True, False
string ''This is a sample string''
Variables
Variables which are introduced into a program are given ''identifiers'' by the programmer. An
identifier is a name, made up from letters and digits, starting with a letter. The length of a name

82 Chapter 8.
is physically determined by the length of a source line, although only the first 8 characters are
significant. Some words are ''reserved'', and have a special meaning in the language. Therefore
they may not be used as names for variables. The reserved words are:
REPEAT WHILE READ ELSE FOR MOD GE LE
OR UNTIL HALT THEN AND IF GT LT
CWHILE WRITE CFOR CIF NOT NE EQ
Before use, variables have to be declared first. Declarations for the different types look like this:
integer i,j,nsets
real f, pi
logical quit
string message
string\Lambda10 keyw
The value of a variable can be substituted in a string by prefixing the name with a percent sign
(%): ''The number is: %num !!'' At runtime the sequence '%num' will be replaced by the actual
value of the variable num.
Remarks:
­ to put a percent sign in a string, it should be prefixed by another percent sign
­ to get a variable substitution followed by a letter or digit, separate them with an
underscore ( )
Expressions
COLA has three kinds of expressions: arithmetic, logical and string. Arithmetic expressions are
made up from integer or real constants, variables and the arithmetic operators:
+ plus
\Gamma minus
\Lambda times
= divide (DIV for integer arguments)
MOD modulo function
For logical expressions the relational operators:
= or EQ equal
!? or NE not equal
! or LT less than
!= or LE less or equal
? or GT greater than
?= or GE greater or equal
and the logical operators: AND, OR and NOT can be used. Example expressions:
5
num
2*(num+3)
num ! 10

Advanced use of GIPSY. 83
(a LE b) OR (c ? 0)
Assignment
An assignment gives the value of an expression to a variable. Example:
nr = 3
subset = subset + 1
message = ''Processing set: ``%iset''
quit = ( num ? last )
8.4.3 Cola statements
Task statement
The task statement is the most important one of COLA. It is used to start a servant task. The
statement itself is just a string. Since these strings have to be passed through to Hermes, they
receive a special treatment:
­ lowercase letters are replaced by their uppercase equivalents
­ multiple spaces are replaced by single spaces
It is also possible to continue one string over more than one line. Examples:
''VIEW,INSET=``%set ``%subset''
''print,inset=aurora freq 1,
box=,format=xxx.xx''
The last one just becomes:
''PRINT,INSET=AURORA FREQ 1,
BOX=,FORMAT=XXX.XX''
READ statement
This statement is used to read a new value for a variable from the console. Variable with the
same name as keywords might cause problems. The user can enter a new value, or keep the
current (by default). You also have the option to specify a prompt string for the Task Status
Area.
Example: The statement sequence
MYSET = ''AURORA''
READ ''Name of set [``%MYSET] ? '' MYSET
leads to the following question at the console:

84 Chapter 8.
­ COLA * Name of set [AURORA] ?
COLA ,MYSET=
If you omit the prompt string, COLA will display:
''Value for !variable? ''
Of course it is also possible to supply a value when starting up the program with:
COLA, NAME=somename , SET=AURORA
WRITE statement
This statement writes a string to the screen (and log file). It is made up of the keyword WRITE
and a string. Example:
WRITE ''Now processing set ``%set ``%subset''
N.B. The first character of the string is treated as a fortran carriage control character (1 gives
newpage, etc)
HALT statement
A HALT statement immediately stops the execution of a COLA program. This can be used to
stop a program if a task stops abnormally.
IF statement
The IF statement allows a choice between two possible statement paths:
IF logical expression THEN
...
ELSIF logical expression THEN
...
ELSIF ...
.
.
ELSE
...
CIF
The ELSIF's and/or ELSE parts of this statement may be omitted.

Advanced use of GIPSY. 85
FOR statement
This statement can be used to execute a body of statements a (fixed) number of times. It takes
the following form:
FOR cv = lwb , upb , step
...
CFOR
The variable 'cv' is the control variable, 'lwb' and 'upb' (resp. the initial and final value) are
general (arithmetic) expressions and 'step' is an integer constant which denotes the step size.
The last may be omitted.
Remarks:
­ although the control variable shouldn't be changed inside the
loop, there's no checking against it (but I'm working...)
REPEAT and WHILE statement
These two statements can be used to repeat a body of statements an (in advance unknown)
number of times. The statements take the following form:
WHILE logical expression
...
CWHILE
and
REPEAT
...
UNTIL logical expression
The program COLA is used as an interpreter of your COLA file. It can also list source and
generated code, make a storyboard and has some control over canceling keywords (See cola.dc1).
8.5 Using different machines
Still to come.
8.6 Programming in GIPSY
For people who want to make minor changes in existing GIPSY programs, or want to write
major new applications, there is a Programmers Guide available. The aim of this document
is to introduce new applications programmers to the GIPSY programming environment. It is
assumed that the new applications programmer is acquainted with some basics about computer
languages, so that he or she can easily learn how to write GIPSY programs in SHELTRAN or
FORTRAN. More experienced programmers can write GIPSY applications in C. Furthermore
it is assumed that the applications programmer is an experienced GIPSY user.

86 Chapter 8.

Part II
The GIPSY architecture
87


Chapter 9
System architecture
9.1 Introduction
This chapter gives an overview of the system architecture of GIPSY. Section 9.2 describes
the development of the GIPSY system. Section 9.3 gives a general introduction to X Window
System, the protocol for the network GIPSY is part of. Section 9.4 presents an overview of the
components of the GIPSY system. The other sections describe these different components of
GIPSY in more detail.
9.2 History
GIPSY started in 1971 as a large single, interactive program. It ran on a PDP­9 computer with
a single­user operating system and modest hardware resources. It could only process WSRT
continuum data. In 1976, GIPSY also ran on a CDC 6600, with a multi­user operating system.
To GIPSY's processing capabilities, WSRT line data reduction facilities were added. In the late
seventies, GIPSY became a set of independent programs. This independency prevented that
faults in one application influenced the whole system. A PDP 11/70 computer replaced the
PDP­9. An M70E image processing computer, connected to the PDP 11/70, provided advanced
image processing and display facilities. At the same time, processing of TAURUS data was
implemented in GIPSY.
In 1979, the master control program HERMES was added to the system to make it more user­
friendly. In 1984, the PDP 11/70 computer was replaced by a VAX 8600. As a result, GIPSY
had to be adapted to the operating system VMS: many software modules had to be rewritten.
Some years later, GIPSY could also process VLA image data, IRAS post­map data, and optical
data from other instruments than TAURUS. Starting in 1990, an effort began to make GIPSY
portable. It now runs under UNIX and has been ported to the following platforms: Alliant(Fx4­
Fx80), SUN (Sparc), DEC 3100, and the HP400 and 700 series. A number of programs to process
IRAS pre­map data were added to the system. For display, GIPSY makes use of the X Window
System. Most of the functionality of the VMS GIPSY is present under UNIX, though further
development will continue over the coming years.
89

90 Chapter 9.
9.3 X Window
sun sparc 1 with server
\Gamma \Gamma @
@
alliant
CLEAN
. .
sun sparc 2
ROTATE
. .
local
LATEX
. .
convex
DISK
. .
alliant
CLEAN
6
?
convex
DISK
sun sparc 2
ROTATE
Figure 9.1: Distributed processing using X Window.
This section should contain some remarks on:
ffl X11 philosophy
ffl windows
ffl display customization (tiled, overlapping, cursor, colors etc.)
ffl client­server model

System architecture. 91
ffl distributed processing (refer to figure 9.1
ffl from here on we say X11 rather than X Window
9.4 System architecture
Figure 9.2 shows the main components of the GIPSY system and its environment and how these
components are connected with each other. The user runs a GIPSY session from a workstation
that is part of a network that uses the X11 protocol. To start up an application program, the user
gives a command to the master control program HERMES. HERMES interprets the command
and starts up the application task. An application consists of a main program and subroutines:
utilities and interface subroutines. For the output of images and plots to the screen and the
plotter, the main program uses the display interface and the plotting interface PGPLOT. To
communicate with the database, it uses the interface GIPSY Database Subsystem (GDS). It
communicates with the user through the user interface. The user and control interfaces are
closely connected to HERMES.
9.5 HERMES
HERMES is GIPSY's master control program. It controls the transfer of messages between parts
of the system. It mediates
ffl between the operating system of the host computer and the user
ffl between the operating system and applications
ffl between applications and the user
ffl between applications and applications
It not just passes the messages, but it also simplifies and improves the communication in many
ways. Some services it offers to the user are
ffl The user need not address the operating system in its own command language.
ffl HERMES provides the user with information about the status of applications in the HER­
MES window. For example, that an application is running, pausing, requiring input, or
has finished its job, either normally or caused by an error.
ffl HERMES keeps a log file of all activities and presents pages of this file on the screen.
ffl The user can store command character strings for frequent use in macros. HERMES re­
places every occurrence of a macro name in the user input by the appropriate character
string.
ffl HERMES stores user input to an application in an application macro. This facilitates
repeating an operation with the same input values.

92 Chapter 9.
user workstation
\Delta \Delta A
A
6
?
host computer/operating system
6
?
?
6
?
6
\Delta \Delta A
A
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C
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C
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C
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interface
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interface
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hermes
x window system
6
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display
interface
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­
oe
pgplot
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?
6
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oe
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6
plotter
main program
6
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6
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gipsy
database
subsystem
6
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ú
ae ú
ae ú
ae ú
ae
¸
oe disk
utility
subroutines
application
program
GIPSY
6
Figure 9.2: GIPSY system architecture.

System architecture. 93
ffl HERMES allows control characters for some frequently used commands.
ffl The user can give input to an application in free format. HERMES converts it into the
format requested by the application and then passes it. Examples of HERMES' user­
friendly input can be found in chapter 4
As figure 9.2 indicates, HERMES is closely connected to the user interface and the control
interface. The user interface is a group of subroutines for the communication between the user
and an application program. The control interface is a group of subroutines. Sections 9.9 and 9.10
discuss these interfaces in more detail.
9.6 GIPSY and X11
This section discusses some customizations of X11 that have been made for GIPSY. It has to
be noted here that advanced users of X11 still have the possibility to change the choices made
for GIPSY according to their own preferences.
GIPSY defines two types of windows: the HERMES window and the display window. The
HERMES window is used to start up GIPSY applications, to provide them with input and to
receive their output. In the display window, plots and images appear.
In GIPSY, windows have a rectangular form. The focus window is the window that contains the
pointer. When a window gets focus, it appears in the foreground.
While GIPSY applications are running, non­GIPSY programs, with their own windows, may be
started as well. They may run on the same, but also on other computers.
To run GIPSY, it is not necessary to use X11. It can also be run from a VT100 compatible
terminal, with a character display. Then, the screen functions only as a HERMES window and
there is no display of plots and images possible. Furthermore, X Window System itself can create
a so­called xterm window that functions as a VT100 compatible terminal.
9.7 Database
Data enter GIPSY in FITS (Flexible Image Transport System) format. Data transfer programs
convert FITS files into files in the internal GDS (GIPSY Data Structure) format.
The database consists of logical units called sets. A set contains data and their header informa­
tion. The data structure can be seen as an n­dimensional array. The header information consists
of descriptor items with associated values. These items are defined according to the FITS stan­
dard or are of any computer supported type, for example, a real or a character. They describe
the data in a set. Some apply to all data in the set, others only to the data of a subset.

94 Chapter 9.
\Delta
\Delta
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\Delta
\Delta \Delta
x­axis
y­axis
z­axis
cube or set
cube headers
. .
6
plane subset
plane headers
. .
\Phi
\Phi
\Phi
\Phiú
column subset
column headers
. .
S
S
S
S
S
S
So
pixel subset
pixel headers
. .
@
@
@I
row subset
row headers
. .
\Phi
\Phi
\Phi
\Phi
\Phi
\Phiú
Figure 9.3: Subsets in a three­dimensional set

System architecture. 95
A subset of an n­dimensional set is an m­dimensional part of the set, m being smaller than or
equal to n; the subset contains all data and related header information in the m­dimensional
sub space of the set.
Example Figure 9.3 shows the possible subset types in a three­dimensional set, a cube:
ffl the cube itself, a three­dimensional subset
ffl planes parallel to the lateral planes of the cube, two­dimensional subsets
ffl rows and columns parallel to the main axes of the cube, one­dimensional subsets
ffl pixels, zero­dimensional subsets
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box
6
area
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oe
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6
Figure 9.4: Frames in a three­dimensional set

96 Chapter 9.
Each subset can be characterized by one or more descriptor items. Header information on a
subset can be attached to the subset itself or to subsets encompassing it.
In addition to subsets, GIPSY defines frames. A frame is a part of the data of an m­dimensional
subset. Such a part is also m­dimensional, but has for one or more of its dimensions not the full
range of values at that dimension.
Example Figure 9.4 shows the possible types of frames in a three­dimensional set:
ffl a box, as part of the cube (sub)set
ffl areas, as parts of plane subsets
ffl lines, as parts of row and column subsets
Header information on a frame is found in the descriptor items of the subsets encompassing it.
9.8 Database interface: GIPSY database subsystem
Through GIPSY Database Subsystem (GDS), an application program accesses the database.
GDS contains the following types of subroutines:
ffl basic routines, that create, delete, and close files, test their existence, and increase the
number of their dimensions
ffl image read/write routines, that retrieve and store image data
ffl descriptor read/write routines, that retrieve and store descriptor items
ffl coordinate routines, that transform coordinates of one system into coordinates of another
system
Image read/write routines select a whole file or a part of it. Parts can be subsets or frames.
Descriptor read routines retrieve specified header information of a specified subset. If they find no
relevant header information on that subset itself, then they search for it on subsets encompassing
it.
Coordinate routines can transform physical coordinates into grid coordinates and grid coordi­
nates into file coordinates. To access data in the database, programs need their file coordinates.
File coordinates indicate where data are stored on disk. To process data, programs need their
grid coordinates. The user can specify data by grid coordinates as well as by physical coordinates.
9.9 User interface
An application program communicates with the user through the user interface. This commu­
nication is not direct but via HERMES. For example, when an application program needs user
input, it sends a message to HERMES. HERMES can pass this message to the user, but it also
can return the desired input from an application macro.

System architecture. 97
The user interface consists of input and output subroutines.
Input subroutines allow an application to select the parameter values that it needs for its ex­
ecution. It sends to Hermes a request to give a value to a certain parameter name. In GIPSY
terminology, a parameter name is called a keyword. The keyword value can be obtained in a
number of ways (see chapter 4).
Examples of output subroutines are
ffl ANYOUT, that sends text to the screen and/or HERMES' logfile
ffl ERROR, that sends error messages to the screen
ffl STATUS, that sends information about the program execution
to the screen
9.10 Control interface
still to come
9.11 Display interface
Display application programs use the display interface (GIDS) to send images and related in­
formation to the display window on the screen. The display window contains a menu of options
that enables the user to adjust the color, contrast, and other features of the displayed image.
9.12 Plot interface: PGPLOT
Plot applications use the plot interface to send plots and related information to the display win­
dow on the screen or to a plotter. GIPSY uses the plot interface PGPLOT, a standard package.
For some functions, PGPLOT uses subroutines of GIPSY's display interface, for example, to
display coordinate frames.
9.13 Application programs
For GIPSY programmers, the main programming languages are SHELTRAN and C. A SHEL­
TRAN precompiler translates SHELTRAN source text into FORTRAN source text, which sub­
sequently is processed by a standard FORTRAN compiler.
Figure 9.5 shows the structure of a GIPSY application program. (For a more detailed picture,
see the dashed box in figure 9.2.) The levels indicate the distance to the operating system, level
3 being most close to it. The core part of an application is the main program. To fulfill some of
its tasks, it makes calls to subroutines: standard interface subroutines and utility subroutines.
The standard interface subroutines perform frequently used tasks that can be subdivided ac­
cording to function:
ffl database interface subroutines

98 Chapter 9.
level 3: standard interface subroutines
level 2: utility subroutines
level 1:
main program
Figure 9.5: Application program structure
ffl display interface subroutines
ffl plot interface subroutines
ffl user interface subroutines
ffl control interface subroutines
The utility subroutines perform a variety of tasks that most programs use, for example, sorting
algorithms.
The documentation of applications shows three levels:
ffl main program documents, with the title format !PROGRAM NAME?.DC1, for example,
RDFITS.DC1.
ffl interface subroutine documents, with the title format !SUBROUTINE NAME ?.DC2,
for example, ANYOUT.DC2
ffl utility subroutine documents, with the title format !SUBROUTINE NAME?.DC3, for
example, BACKUP.DC3

System architecture. 99
In addition to these documents, there are level zero documents, providing general information
about the GIPSY system, for example, SOFTWARE.DC0, logging current software develop­
ments.

Appendix A
GIPSY commands
A.1 Keyword syntax
A.2 List of GIPSY tasks
Tables A.1 lists all GIPSY tasks that are avalable on October 4, 1995.
100

GIPSY commands. 101
Program Purpose
ADD Add a series of input subsets and one or another
AID Selects one of the tasks SUB, MUL, ADD, DIV or CONDIT.
ANTPAT Calculate beamwidth and position angle of synthesized beam.
AOSNIP Snip AO­scan into seperate legs
BLOT Conditional transfer of maps using blotch region.
BUG reports ( a fix of ) a bug.
CBLANK Converts datavalues to BLANK and vice versa.
CLEAN This program cleans maps
CLIP Blank values of input if they are outside range.
CODER Create C­code for simple programs.
COLA Control language for use with Hermes.
COLOUR Loads a COLOUR Look Up Table in GIDS. This LUT can be
activated with the USER button in the COLOR menu.
COMBIN Combine sets to create new sets using mathematical
expressions
CONDIT Transfer values if test value within certain range.
CONREM Removes continuum from channel maps by fitting a
polynomial to the continuum channels.
COORDS Converts user supplied coordinates into physical coordinates.
COPY Program to copy set and subsets. It can also increase or
decrease the frame size of the subsets. BLANKs will be
written in the output set outside the original subset frame.
CORMAP Check whether there is a correlation between two maps.
CPLOT contour and gray scale plot
CREATE Creates a SET (and subsets)
DECIM Decimate set in any direction with an integer factor
DELETE Delete sets
DISK DISK lists the contents of the current directory and
lists some properties of sets.
DIV Divides a series of input subsets by one or another
series of subsets.
EDITSET Program to edit data in a set.
ELLINT Programme fits an ellipse to an user defined bunch of points.
ELLFIT Integration of map in ellipses.
ENHANCE Enhance image (Local enhancement method)
FIXHED Add, change, delete or list item(s) in set header.
FIXSNIP Adds the keywords OBS and SCANTYPE to the header
if these are not present in an IRDS.
FLAT Apply a flat field correction to a map by fitting a
2­D polynomial to the background.
FLUX Program to calculate flux in user defined box.
Table A.1: List of available GIPSY tasks as of October 4, 1995

102 Chapter A.
Program Purpose
GAUFIT GAUFIT calculates initial estimates and/or fits multi­
component gaussians to profiles.
GAUPROF GAUPROF examines influence of parameters in GAUFIT by
plotting Gaussian estimate and fit of a selected profile.
GIDS Description of the Groningen Image Display Server.
GRADIENT Calculates the gradients or the laplacian of a
map, using three by three sized templates.
HEADER Display header information
HERMES Master control program for GIPSY.
HISTOG Program creates histogram of intensities in a set
IMAGE Imager and/or destriper for IRAS
INIDISPLAY Initializes the display for GIPSY applications.
INSERT Program to insert (parts of) a set into another existing set.
IOTEST Tests the speed of disk io.
IRDSPOS Extract projected sky positions from positions
IRSET Generate a test IRDS
LFITS List FITS files on a tape
LRSCAL Generate a calibrated LRS spectrum from data in an IRDS
MEAN Program to calculate the mean of a number of subsets.
MERGE Merges a number if IRDS's.
MIRROR Mirrors a two­dimensional image in x, y or both.
MNMX This program finds the minimum and maximum value in a
subset or part of a subset. It also counts the number
of blanks.
MOMENTS Program to calculate moments and other properties
MTCOPY Copies selected files from one tape device to another
MUL Multiplies a series of input subsets with one or
another series of subsets.
NEWS Displays the GIPSY news which you have not yet seen.
NHERMES GIPSY master control program for a non interactive environment
NOHERMES Provide user communication and process control functions
OUTAGE Remove possibly corrupt data around outage from irds
PATCH Patch up a map, by interpolating through holes.
PBCORR Corrects maps for primary beam correction
PGDEMO Demonstrates PGPLOT.
PLATE Snips raw data from tape(s) to custom plate
PLSCAN Plots raw IRAS scans
PPLOT Plot the intensity along a line through a set.
PRINT Print part of a (sub)set on terminal/printer.
QFIT Fit 2­dim gaussian to data in box
QPLOT QPLOT plots an one dimensional slice through a set.
RDBPHF Add BPHF information to an existing IRDS
REPROJ Transfers sky map from one coordinate system to another
RESTORE This program restores the residual map(s) created by CLEAN.
Table A.2: List of available GIPSY tasks as of October 4, 1995 (cont.)

GIPSY commands. 103
Program Purpose
REWIND Rewinds a tape.
RFITS Load FITS files from tape into a GIPSY set.
RHEAD List header elements ( descriptors ) and their level in grids
SCALE Program to scale the data in subsets by a factor and an offset
SKIP Skips files forward or backward on tape
SLICE Make a slice through a set
SMOOTH Smooth sets with a gaussian beam
SNIPIN Generate a test IRDS
STAT Program to calculate elementary statistics in user
defined box(es).
SUB Subtract one or a series of subsets from another
series of subsets.
SUM Program to add a number of subsets.
TABLE GIPSY Table maintenance program
THERMES GIPSY master control program for ASCII terminals
TRACE TRACE plots image values at user given positions
TRACKS Plots IRAS tracks.
VELSMO Program does a one dimensional smoothing of subsets.
VIEW Displays two dimensional images.
WEED Copies snips to an irds (or part of it), or removes snips.
WFITS Writes disk set and subsets onto magnetic tape in
in FITS format
XHERMES GIPSY master control program for X Window
ZODYCAL Zodiacal emission calibration program
Table A.3: List of available GIPSY tasks as of October 4, 1995 (cont.)

Appendix B
Sky Projections used in GIPSY
GIPSY knows about 4 Sky coordinate types. The kind of coordinate is conveyed into the first
characters of the axis type as `RA: : : ', `DEC: : : ' etc. The Sky coordinates known are:
`RA' Equatorial, Right Ascension
`DEC' Equatorial, Declination
`GLON' Galactic Longitude
`GLAT' Galactic Latitude
`ELON' Ecliptic Longitude
`ELAT' Ecliptic Latitude
`SLON' Supergalactic Longitude
`SLAT' Supergalactic Latitude
GIPSY knows of 10 different projections from rectangular grids to sky coordinates and vice
versa. This chapter discusses all these projections. The type of geometry is conveyed in the last
characters of the axis type, as `: : : TAN', `: : : NCP', etc. The known projections are:
`AIT' Aitoff equal area projection
`CYL' Equivalent Cylindrical projection
`FLT' Flat projection
`TAN' Gnomonic projection
`SIN' Orthographic projection
`ARC' Rectangular projection
`GLS' Transversal projection
`NCP' Nort Celestial Pole projection
`STG' Stereographic projection
`MER' Mercator projection
To separate the coordinate type from the projection type at least one minus­sign (\Gamma) must be
present (`RA\GammaNCP', `DEC\GammaNCP').
In a projected plane, the position of a point (x; y) with respect to the coordinate reference point
in an arbitrary linear system may be represented as
x = Lcos(ae) +Msin(ae)
104

Sky Projections used in GIPSY. 105
y = Mcos(ae) \Gamma Lsin(ae)
where ae is a rotation, L is the direction cosine parallel to latitude at the reference pixel, and M
is the direction cosine parallel to longitude at the reference pixel. Both the (x; y) and (L; M)
systems are simple linear, perpendicular systems. If we represent longitude and latitude with
the symbols ff and ffi and the projection centres with ff 0 and ffi 0 , we get the conversion routines
shown in the following sections.
B.1 Aitoff equal area projection
L =
2f ff cos(ffi)sin( ff\Gammaff 0
2 )
Z
M = f ffi sin(ffi)
Z
\Gamma M 0
where
Z =
s
1 + cos(ffi)cos( ff\Gammaff 0
2 )
2
M 0 = f ffi sin(ffi 0 )
q
1+cos(ffi 0 )
2
B.2 Equivalent Cylindrical projection
L = ff \Gamma ff 0
M = sin(ffi \Gamma ffi 0 )
B.3 Flat projection
L = (ff \Gamma ff 0 )
M = (ffi \Gamma ffi 0 )
B.4 Gnomonic projection
The Gnomonic projection is common in optical astronomy.
L = cos(ffi)sin(ff \Gamma ff 0 )
sin(ffi)sinffi 0 + cos(ffi)cos(ffi 0 )cos(ff \Gamma ff 0 )
M = sin(ffi)cos(ffi 0 ) \Gamma cos(ffi)sin(ffi 0 )cos(ff \Gamma ff 0 )
sin(ffi)sinffi 0 + cos(ffi)cos(ffi 0 )cos(ff \Gamma ff 0 )

106 Chapter B.
B.5 Orthographic projection
The Orthographic projection is used by the VLA.
L = cos(ffi)sin(ff \Gamma ff 0 )
M = sin(ffi)cos(ffi 0 ) \Gamma cos(ffi)sin(ffi 0 )cos(ff \Gamma ff 0 )
B.6 Rectangular projection
The Rectangular projection is used in Schmidt telecopes.
L = `
sin(`) cos(ffi)sin(ff \Gamma ff 0 )
M = `
sin(`)
i
sin(ffi)cos(ffi 0 ) \Gamma cos(ffi)sin(ffi 0 )cos(ff \Gamma ff 0 )
j
where
cos(`) = sin(ffi)sin(ffi 0 ) + cos(ffi)cos(ffi 0 )cos(ff \Gamma ff 0 )
B.7 Global Sinusoidal projection
L = (ff \Gamma ff 0 )cos(ffi)
M = (ffi \Gamma ffi 0 )
B.8 North Celestial Pole projection
The North Celestial Pole projection is used by the WSRT.
L = cos(ffi)sin(ff \Gamma ff 0 )
M = cos(ffi 0 ) \Gamma cos(ffi)cos(ff \Gamma ff 0 )
sin(ffi 0 )
B.9 Stereographic projection
L = 2 cos(ffi)sin(ff \Gamma ff 0 )
1 + sin(ffi)sin(ffi 0 ) + cos(ffi)cos(ffi 0 )cos(ff \Gamma ff 0 )
M = 2 sin(ffi)cos(ffi 0 ) \Gamma cos(ffi)sin(ffi 0 )cos(ff \Gamma ff 0 )
1 + sin(ffi)sin(ffi 0 ) + cos(ffi)cos(ffi 0 )cos(ff \Gamma ff 0 )

Sky Projections used in GIPSY. 107
B.10 Mercator projection
L = f ff (ff \Gamma ff 0 )
M = f ffi ln
i
tan( ffi
2 + ú
2 )
j
\Gamma M 0
where
f ff = cos(ffi 0 )
f ffi = \Delta ffi
ln
i
tan( ffi 0 +\Delta ffi
2 + ú
2 )
j
\Gamma ln
i
tan( ffi 0
2 + ú
2 )
j
M 0 = f ffi ln
i
tan( ffi 0
2 + ú
4 )
j

Appendix C
GIPSY files
C.1 Important files
ffl gipsy local.dc0
ffl manual.tex
C.2 Where are they?
GIPSY email address:
gipsy@[129.125.6.204]
gipsy@[129.125.6.205]
108

Appendix D
Host computer and operating
system
At present, GIPSY runs on the following computers:
ffl Alliant, with the operating system Concentrix
ffl DEC 3100, with the operating system Ultrix
ffl HP9000, with the operating system HP­UX
ffl SUN, with the operating system SunOs
Concentrix, Ultrix, HP­UX, and SunOs all are UNIX dialects. The user need not have any
knowledge about UNIX or VMS to work with GIPSY. Hermes intermediates between the user
and the operating system.
109

Appendix E
Hardware requirements
To work with GIPSY, the following hardware devices are minimally needed:
ffl a host computer
ffl a VT100 compatible terminal, for example, a PC, or a workstation
On a VT100, the screen functions only as a Hermes window and no images or plots can be
displayed.
To make hard copies of plots, a Postsript printer is required. For hard copies of, e.g., the logfile,
tape listings, etcetera, an ASCII printer is required.
110

List of Figures
2.1 The layout of the GIPSY screen as setup by HERMES : : : : : : : : : : : : : : : 7
7.1 IRAS orbital geometry : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 68
7.2 IRAS focal plane : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 69
7.3 Timing of IRAS data : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 71
7.4 Sample Custom Plate : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 72
7.5 GIPSY implementation of a single snip : : : : : : : : : : : : : : : : : : : : : : : : 73
7.6 GIPSY implementation of an IRAS Data Structure (IRDS) : : : : : : : : : : : : 73
9.1 Distributed processing using X Window. : : : : : : : : : : : : : : : : : : : : : : : 90
9.2 GIPSY system architecture. : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 92
9.3 Subsets in a three­dimensional set : : : : : : : : : : : : : : : : : : : : : : : : : : 94
9.4 Frames in a three­dimensional set : : : : : : : : : : : : : : : : : : : : : : : : : : : 95
9.5 Application program structure : : : : : : : : : : : : : : : : : : : : : : : : : : : : 98
111

List of Tables
2.1 Some GIPSY position input formats : : : : : : : : : : : : : : : : : : : : : : : : : 9
3.1 Possible GIPSY axis names : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 13
3.2 Units recognized by GIPSY : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 19
3.3 Possible GIPSY position input formats : : : : : : : : : : : : : : : : : : : : : : : : 19
4.1 HERMES commands : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 31
4.2 HERMES commands (cont.) : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 32
5.1 Sample output of DISK : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 37
5.2 PRINTER= menu : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 38
5.3 HEADER output : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : : 39
5.4 FIXHED, ITEM=HEAD output : : : : : : : : : : : : : : : : : : : : : : : : : : : : 40
5.5 Mouse actions using the Cursor option in GIDS : : : : : : : : : : : : : : : : : : 43
A.1 List of available GIPSY tasks as of October 4, 1995 : : : : : : : : : : : : : : : : : 101
A.2 List of available GIPSY tasks as of October 4, 1995 (cont.) : : : : : : : : : : : : 102
A.3 List of available GIPSY tasks as of October 4, 1995 (cont.) : : : : : : : : : : : : 103
112