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Astronomical Data Analysis Software and Systems VII
ASP Conference Series, Vol. 145, 1998
R. Albrecht, R. N. Hook and H. A. Bushouse, e
Ö Copyright 1998 Astronomical Society of the Pacific. All rights reserved.
ds.
HST Paper Products: A New Way to Look at HST Data
W. Hack
Space Telescope Science Institute, 3700 San Martin Dr., Baltimore,
MD, 21218, Email: hack@stsci.edu
J.­C. Hsu
Space Telescope Science Institute, 3700 San Martin Dr., Baltimore,
MD, 21218, Email: hsu@stsci.edu
Abstract. Two new instruments, STIS and NICMOS, were added to
HST during the SM97 servicing mission, each with new types of data that
need to be processed. As a result, a completely new system for generating
paper products was created which provides a detailed summary of the ob­
servations and of the calibrations applied to the observations in the HST
pipeline. This new version of the paper products generating software pro­
duces a totally redesigned summary for the older instruments (WFPC2,
FOS, GHRS, and FOC) as well as creating paper products for the newly
installed STIS and NICMOS. In this paper, we discuss the design and
algorithms used to handle the extremely large amounts of data produced
by the instruments on board HST, as well as the new task's limitations.
This new version of the HST paper product software is now available in
STSDAS Release V2.0.
1. Introduction
The Hubble Space Telescope (HST) not only generates a great deal of data in a
single day, but a wide variety of data as well ­ from 1­D and echelle spectra to
images and time­tag data. All of this data is processed on the ground to apply
basic instrumental calibrations and prepare the data to be ingested into the HST
archive and then analyzed by the observer. One final step in this processing is
to create a summary for initially judging the quality of the observations and for
determining the status of the calibrations applied to the data. This summary,
however, must be e#cient in its reporting and yet comprehensive enough in
its results to be useful. Generating such a report for each instrument's data
(WFPC2, FOC, FOS, GHRS, STIS and NICMOS) while retaining a similar
enough format for easy comprehension was the primary goal for the software.
In addition, the software must run quickly enough to prevent backlogs when
ingesting into the archive. These two primary problems guided our e#ort to
create a single software system to provide summaries known as `paper products'
for all HST data. This paper will summarize the major features of this software
system.
308

HST Paper Products: A New Way to Look at HST Data 309
2. Overview of Data Processing
The paper products software performs the following steps in creating the sum­
maries for each set of observations:
. Sorts input data: Input data can be a combination of one or more
instrument's data from any number of proposals. The input data can
either be in FITS format, as if obtained from the HST DADS system, or
GEIS format. All of the observations, or only selected observations, can
be processed at one time depending on the user's input. A separate output
file with its own cover page and summary will then be created for each
logical unit defined by data from each instrument used in each proposal.
. Summarizes each observation: The basic exposure information for all
observations in the proposal is provided in a tabular form. It includes
target data, instrument configuration (such as filters used), and basic data
statistics. Observations for each instrument are handled by their own func­
tion, allowing the summary to reflect the unique nature of each instrument.
. Displays the data for each observation or observation set: Grey
scale images or plots of the data are provided for each exposure. These
displays are created using SPP functions or CL scripts tailored specifically
for the type of data produced by each instrument. In addition to the
graphical display of the data, a summary of the exposure information is
also provided. The basic forms of displaying the data are given for each
instrument:
Table 1.
FOS Target acquisition position plots, spectral plots, total flux plots
GHRS spectral plots, jitter plots
FOC image display
WFPC2 mosaic of CCD images, single chip display
NICMOS thumbnail index of images, mosaiced images, target acquisition images
STIS image display, spectral plots, jitter images, target acquisition images
. Provides a summary of the observations data quality: The last
page(s) of the paper products is a summary of the calibration(s). A sum­
mary of pointing information (jitter data), explanations regarding quality
flags and some basic image statistics are all reported here with an exhaus­
tive list of calibration files and the origin of each file.
. Process the IGI scripts: The results from all the processing are gen­
erated in the SPP procedures and CL scripts as IGI commands, then
processed by IGI to produce the final output.
This processing will produce a report tailored to each instruments data and
contain the following estimated number of pages:

310 Hack and Hsu
Table 2.
Cover Page and Help Page 1 Page each
Help Page 1 Page
Exposure Summary 1+ Pages
Data Display 1 Page/observation (FOC)
1­ 2 Pages/external observation (WFPC2)
1­3 Pages/observation (FOS)
1+ Page/observation (STIS)
32 dithered obs/page + 1 page/image (NICMOS)
Observation Summary 1­2 pages
HST archive operations currently used Helvetica narrow fonts for all paper
products. Use of di#erent fonts may cause overlapping of text in the report.
3. Operation of the Software
The paper products software was designed to be run within the IRAF CL envi­
ronment. The package consists of one primary task, pp dads, and many hidden
tasks to control each instrument's output. The pp dads task only uses a small
number of parameters; namely, input, device, fits conv.
The parameter input controls which files are read in for processing, including
using wildcards, list files or simply one image name. The parameter device can
be set to a PostScript device to create PostScript files or a printer queue to send
the output directly to a printer. This relies on using IRAF's printer queues,
graphics kernels, and STSDAS's PostScript kernel.
4. Use of FITSIO
All HST data is routinely delivered to observers on tape in FITS format, and
archived in the DADS system in FITS format as well. The paper products
software, therefore, relies on the latest FITS kernel in IRAF to work with STIS
and NICMOS data whilst also working directly with FOC, WFPC2, FOS, and
GHRS data that are stored in the GEIS format.
5. SPP, CL and IGI
Most data processing is handled by routines written specifically for each instru­
ment's data. These functions are written in SPP for NICMOS, FOC, WFPC2,
and FOS, while CL scripts are used to process STIS and GHRS observations.
Modular design can be readily modified for each instrument or even have new

HST Paper Products: A New Way to Look at HST Data 311
code added to support future new instruments. The use of SPP provides e#cient
access to image headers, the ability to perform statistical calculations while the
image remains open, and great control of the output as IGI commands. The
CL scripts used for STIS and GHRS are readily edited and can be used without
compiling, however, they lack the e#cient file I/O that SPP o#ers.
The results of the calculations and instructions for displaying the data are
sent to an output file to be interpreted by IGI, the Interactive Graphics Interface.
This provides several advantages for creating the paper products:
. manages image display: graphics and images can be displayed with im­
age resizing being done as needed on the fly, enabling creation of thumbnail
indices and annotated image
. machine independent and flexible output: IGI uses IRAF's graphics
kernels and PostScript kernel to create PostScript output for any platform.
6. Computational E#ciency
The paper products software must run fast enough to keep up with the data
stream coming from HST in order to avoid backlog. This led to the use of
SPP code to generate the paper products for most instruments. In general, the
computation of the paper products takes from 30­60 seconds per observation
on a Sparc 5 workstation with only one user, and about 2­3 minutes per obser­
vation on a DEC Alpha workstation with several users. This is quick enough
to avoid most backlog situations. The real bottleneck is the printing of the
paper products. A local Printserver 17 printer can print about 15­20 Mb of
PostScript output in an hour, however, the paper products code can generate
24Mb of PostScript in about 6 minutes on a Sparc 5, or about 20 minutes on
an Alpha workstation. Therefore, a great deal of emphasis has been placed on
setting up ways to print these jobs in parallel on multiple printers to keep up
with the stream of data coming from HST. A drawback to this is the need for
large temporary disk space for block averaged WFPC2/STIS/NICMOS images,
PostScript files, and temporary IGI files and an e#ort is being made to reduce
this need.
7. Summary
The new paper products package within STSDAS can process observations from
a mix of instruments in one pass resulting in clear and concise documentation.
It relies on many of IRAF's built­in functionality as well as many separate
IRAF/STSDAS tasks to produce the paper products. The following packages
are necessary for the operation of the paper products software: IRAF Version
2.10.4p2, or newer (preferably Version 2.11) and STSDAS/TABLES Version
1.3.5, Version 2.0, or newer. The simple, one task interface makes it easy to run,
both interactively by a user after extracting data from DADS and in batch mode
from a script, as done by the HST archive. This experience with processing daily
observations has proved that this task can function e#ciently and e#ectively with
minimal intervention.