Документ взят из кэша поисковой машины. Адрес оригинального документа : http://xmm.vilspa.esa.es/sas/7.1.0/doc/phasecalc.ps.gz Дата изменения: Mon Jul 9 09:06:10 2007 Дата индексирования: Tue Oct 2 07:18:30 2012 Кодировка: Поисковые слова: ngc 5128

XMM-Newton Science Analysis System Page: 1
phasecalc
July 9, 2007
Abstract
Given an ephemeris, calculate a phase column for an event table.
1 Instruments/Modes
Instrument Mode
all all modes with time information
2 Use
pipeline processing yes (?)
interactive analysis yes
3 Description
Given an ephemeris and a list of event tables, phasecalc calculates the phase of each event in each of the
tables. The calculated values are stored in a column named PHASE. If the column exists it is overwritten.
phasecalc relies on the event table having a TIME column and the two attributes MJDREF and TIMEZERO.
 MJDREF is the Modied Julian Day from which times are calculated.
 TIMEZERO is the clock correction at the start of the observation in seconds.
 phasecalc also uses the TIMESYS keyword to determine the Time System (UTC, TT, TAI)
used in event table. If the TIMESYS keyword is not UTC, the Reference Epoch time of the
ephemeris is converted to the appropriate Time System. In the absence of this keyword TT
(XMM Time) is assumed.
The time of event n is then:
t(n) = MJDREF  86400 + TIMEZERO + TIME[n] (1)
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where TIME[n] is the value stored in the TIME column.
An ephemeris is specied in terms of four quantities:
 reference epoch t 0 ; This is UTC.
 reference phase  0 ;
 frequency  in Hz;
 frequency time derivative _
 in Hz/s.
The phase of event n is dened as:
(n) =  0 + ft(n) t 0 g   +
1
2
ft(n) t 0 g 2  _
 : (2)
3.1 Examples
 phasecalc --tables=events.ds:EVENTS --frequency=29.8309503578 --frequencydot=-374213.62e-15
--epoch=2001-04-01T00:00:00
Calculate the phase of each event in events.ds:EVENTS for the given ephemeris.
4 Parameters
This section documents the parameters recognized by this task (if any).
Parameter Mand Type Default Constraints
tables yes T set.ds:EVENTS
List of tables to operate on.
frequency no r
Frequency [Hz].
frequencydot no r
Frequency dot [Hz/s].
epoch no w
Epoch of the phase in UTC
phase no r
Phase at the epoch.
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5 Errors
This section documents warnings and errors generated by this task (if any). Note that warnings and
errors can also be generated in the SAS infrastructure libraries, in which case they would not be docu-
mented here. Refer to the index of all errors and warnings available in the HTML version of the SAS
documentation.
TimezeroDoesNotExist (error)
The table does not contain the attribute TIMEZERO. The absoulte time of the events cannot
be calculated.
MjdrefDoesNotExist (error)
The table does not contain the attribute MJDREF. The absoulte time of the events cannot be
calculated.
TimeColumnDoesNotExist (error)
The table does not contain the column TIME. The absoulte time of the events cannot be
calculated.
PhaseColumnExists (error)
The PHASE exists, and clobber is not enabled.
SubProcessError (warning)
Move on to the following table.
corrective action: An error was found while processing one of the inout tables. The message
indicates what the table and error ware.
6 Input Files
1. An event dataset that must contain:
 a real64 column TIME;
 the attribute MJDREF;
 the attribute TIMEZERO.
7 Output Files
1. The input data set, modied by the addition of a real64 column PHASE.
8 Algorithm
read ephemeris
open table
if( cannot calculate absolute event time ) error
call selectlib with table and phase formula
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9 Comments
phasecalc is meant to be used in conjunction with evselect or xmmselect to perform second order
ltering.
phasecalc is not a general tool, in that it has a very specic knowledge of how to calculate the absoulte
time of an event based on the XMM-Newton conventions. On the other hand, this aords a paramter
interface focussed on the astronomical data. For a more generic tool to perform arbitrary math on binary
tables see tabcalc ().
10 Future developments
References
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