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11.1 Acronyms

AO ....... Announcement of Opportunity  
ADF ...... Astrophysical Data Facility  
ASCA ..... Advanced Satellite for Cosmology and Astrophysics  
ARF ...... Ancillary Response File  
CCD ...... Charged Coupled Device  
COR ...... Cut-Off Rigidity  
CPU ...... Central Processing Unit 
CTE ...... Charge Transfer Efficiency  
CTI ...... Charge Transfer Inefficiency  
DFE ...... Dark Frame Error  
FITS ..... Flexible Image Transport System  
FOV ...... Field of View  
FWHM ..... Full Width at Half Maximum  
FRF ...... First Reduction File  
FTP ...... File Transfer Protocol  
GIS ...... Gas Imaging Spectrometer  
GOF ...... Guest Observer Facility  
GTI ...... Good Time Interval  
HEASARC .. High Energy Astrophysics Science Archive Research Center  
HK ....... Housekeeping  
HTML ..... Hyper-Text Mark-up language  
HTTP ..... Hyper-Text Transfer Protocol  
ISAS ..... Institute of Space and Astronautical Science  
LHEA ..... Laboratory for High Energy Astrophysics  
mkf ...... mkfilter file  
MPC ...... Multi Pulse Count  
OGIP ..... Office of Guest Investigator Programs  
PHA ...... Pulse Height Analyzer  
PI ....... Pulse Invariant  
PSF ...... Point Spread Function  
PV ....... Performance Verification  
QDP ...... Quick and Dandy Plotter (previously Quick and Dirty Plotter)  
RDD ...... Residual Dark Distribution  
RMF ...... Redistribution Matrix File  
RTI ...... Rise Time Invariance  
SAA ...... South Atlantic Anomaly  
SCC ...... Space Craft Clock  
SIS ...... Solid-state Imaging Spectrometer  
TAI ...... International Atomic Time
TDB ...... Barycentric Dynamical Time
URL ...... Uniform Resource Locator  
UT ....... Universal Time  
UTC ...... Coordinated Universal Time
WWW ...... World Wide Web  
XRT ...... X-ray Telescope

11.2 Software Packages

The following are major software packages commonly used to analyse data once it has been reduced.

Note the a User's Guide for XSELECT, the package used to reduce the data, can be obtained by consulting the URL

11.3 XSELECT Command Sequences

Chapters 5 to 7 on screening and filtering contain extensively annotated ascascreen and XSELECT sessions. Here, however, only sets of command sequences are given, the aim being to provide compact reference points and aides de memoire. In subsequent sections, the following command sequences will be described.

  1. Read several events files into XSELECT directly.

  2. Screen and extract GIS PH mode events data.

  3. Screen and extract SIS BRIGHT and BRIGHT2 mode events data.

  4. Select regions for source and background and extract spectra.

  5. Obtain GIS response matrices.

  6. Obtain or Create SIS response matrices.

  7. Generate the Ancillary Response File (ARF).

  8. Extract an events list to use as a light curve for XRONOS.

  9. Extract FITS rate file to use as a light curve for XRONOS.

  10. Extract soft and hard SKY images.

In the following examples, it is assumed that the events files reside in the directory above the working directory and that the mkf file is in same directory. Since ASCA is the default mission, the set mission asca command has been omitted. The screening criteria used in the examples are not unique and the user should use criteria appropriate for each case and should therefore consult chapters 5 and 6 for more details. We omit SIS FAST mode here, as it is somewhat specialized and does not constitute mainstream ASCA analysis (but full details are given in §4.10).

11.3.1 Read Several Events Files Directly

All the subsequent examples read in data into XSELECT by means of the so-called obscat. However, it is possible to read in several events files directly and in such a case the appropriate commands in the examples should be replaced as described here.

First make an ascii list of all the events files you want to read into XSELECT. For example

ls -1 *s0*.unf > s0.list

At this stage be VERY CAREFUL that you keep SIS FAINT, BRIGHT and BRIGHT2 files in separate places, or else edit them out of the list file. You may duplicate the data. You may also need to select the file list on bit rate.

Then read the files within XSELECT by

read events "@s0.list"

11.3.2 Screen and Extract GIS PH Mode Events Data

This example is based on GIS2.

set datadir ..
set instrument gis2
set datamode ph
make obscat
show obscat
choose 1-**
select mkf
filter region a1060_g2_randc.reg
extract events
save events a1060_g2.evt

Please note that, by not selecting on bit rate, all bit rates are included. To use, say, HIGH bit rate data only, insert the command select obscat bit_rate.eq.'HIGH' after making the obscat. The file a1060_g2_randc.reg contains the lines:


and corresponds to the high background ring and calibration source in GIS2 (see §5.5.2 for GIS3).

11.3.3 Screen and Extract SIS BRIGHT or BRIGHT2 Mode Events Data

This example assumes SIS0 4-CCD mode BRIGHT mode data. The Sn_PIXLm criteria depend on CCD mode (see chapters 5 and 6). Analysis of BRIGHT2 mode data is identical except for the set datamode command.

set instru sis0
set datadir ..
set datamode bright
make obscat
select obscat'LOW'
show obscat
choose 1-**
select mkf
  && s0_pixl0 > 0 &&s0_pixl0 < 50
  && s0_pixl1 > 0 &&s0_pixl1 < 50
  && s0_pixl2 > 0 &&s0_pixl2 < 50
  && s0_pixl3 > 0 &&s0_pixl3 < 50
select events
extract events
save events a1060_s0.evt

Please note that default settings are used with the sisclean command and are entered with a carriage return.

11.3.4 Select Extraction Regions for Source and Background and Extract Spectrum

Here, the assumed starting point is a single, already-screened events list (a1060_g2.evt, in this example). Note that the instrument and data mode do not have to be set because XSELECT reads them from the header of the events list. An image is extracted first to enable a region filter (cf_g2.reg, in this example) to be defined. For more details see §7.3 and §7.5.

set mkfdir ..
set datadir .
read events a1060_g2.evt
extract image
plot image

In SAOimage, use the Scale, Pan and Color buttons to adjust the appearance of the plot. Then hit the Cursor button. Choose a circular region (a circular region is recommended for greatest accuracy). Move the circle so that its center coincides with the source centroid with the left mouse button, and adjust its size with the middle button. Type s at the keyboard to save the region. Hit the region button and then the write button. Name the file (cf_g2.reg, in this example) and hit return. After hitting the reset button we repeat this procedure to define a background region file (back_g2.reg here). The background region does not have to be circular, and is likely not to be for the SIS. Finally, hit the etc button and then quit. Note that `exclusion' regions can be created in SAOimage by typing e instead of s.

Continuing the XSELECT commands:

filter region cf_g2.reg
extract spectrum
save spectrum cf_g2.pi
clear region
filter region back_g2.reg
extract spectrum
save spectrum back_g2.pi

The yes and no which appear in the command sequence are answers to the the question `Group or rebin the spectra before outputting?' The GIS spectra will be grouped but the SIS spectra will be rebinned. In the case of GIS source spectra, the answer should be yes; for GIS background, no. For the SIS the answers for both source and background spectra will be yes in most cases. See §8.1 and §8.3 for more details.

11.3.5 Obtain GIS Response Matrices

For the GIS the latest response matrices, or RMF files, are obtained from the CALDB (e.g. by anonymous FTP to Look in the directory /caldb/data/asca/gis/cpf/ for a sub-directory with a name corresponding to the latest date. As of March 1997, the latest matrices are obtained from


and are called (gis2v4_0.rmf) and (gis3v4_0.rmf) for GIS2 and GIS3 respectively.

11.3.6 Obtain or Create SIS Response Matrices

For ASCA data taken in the PV phase or early AO-1, ready-made SIS response matrices can be obtained by anonymous FTP to from the directory


There are many rmf files in this directory but deciphering the name of just one of them is sufficient to understand what all the rest correspond to. One of the SIS0, chip 1 files is called


The `s0c1' clearly means SIS0, chip 1; g0234 means that the ASCA data must have SIS grades 0,2,3,4 selected; p40 means the so-called `split-threshold' is 40 ADU (this is the case for almost all observations); 512 means that the RMF file has 512 output energy bins; v0.8 means that the matrix was created with program sisrmg, version 0.8, and finally the i means that the spectral files must have PI bins (matrices with h instead of i are appropriate for PHA spectra).

Late into the AO-1 phase, the time-dependence of various aspects of the SIS instrument responses became too large to neglect. In general, the safest option is to generate your own response matrices for all your data, using the FTOOL sisrmg. The `standard' matrices can still be used `Quick-Look Analyses'. If the spectral files were created by XSELECT, sisrmg can obtain almost all of its inputs directly from the spectral files.

11.3.7 Generate the Ancillary Response File (ARF)

To generate the ARF, run the FTOOL ascaarf, giving as input the names of the spectral file and the RMF. The program ascaarf asks for the name of the RMF file for the sole purpose of setting the energy-bin array, although this is optional. The program sisrmg also asks for the name of the ARF file. The way to get around this apparent contradiction (apart from ignoring the question) is to run ascaarf with one of the `standard' SIS response matrices (see §11.3.6 above). See §8.7, 10.6 and 10.7.1 for more details on ascaarf.

11.3.8 Extract Events List to Use as a Light Curve for XRONOS

As described in §9.4, XRONOS can read in events lists and use them as light curves. In this example, we assume that the starting point is an already-screened GIS PH-mode events list (gx301_g2.evt) which the user wants to filter by region and energy.

set mkfdir ..
set datadir .
read events gx301_g2.evt
extract image

Now make a source-extraction region file as described in §11.3.4, and then

filter region source_g2.reg
filter pha_cut 68 170
extract events
save events source_g2_soft.evt

The channel range 68-170 corresponds, in GIS PH mode, to $\sim 0.8-2.0$ keV. See §7.9 for channel-to-energy conversion formulae.

11.3.9 Extract FITS Rate File to Use as a Light Curve for XRONOS

FITS rate files, described in §9.4, can be read into XRONOS. The required steps are identical to those in §11.3.2 or §11.3.3 except for the following.

  1. A temporal binsize must be set (or the default used) with the set binsize command, just before the filter region command.

  2. The commands extract events and save events are replaced with extract curve and save curve respectively.

11.3.10 Extract Soft and Hard Sky Images

In this example, the starting point is an already-screened events list. Apart from setting the energy filters, the only `extra' command is set image sky, which changes the columns for which the image is extracted from DETX/DETY (detector coordinates - the default) to X/Y (RA and DEC).

set mkfdir ..
set datadir .
read events kepler_g2.evt
set image sky
filter pha_cut 68 170
extract image
save image kepler_g2_soft.img
clear pha_cut
filter pha_cut 509 849
extract image
save image kepler_g2_hard.img

The channel ranges 68-170 and 509-849 correspond, in GIS PH mode, to 0.8-2 keV and 6-10 keV, respectively.

11.4 MKF Parameter Summary

Here we list, for reference, all the parameters in the mkf files.

11.4.1 Time-Related Columns

TIME            Seconds from Jan. 1, 1993
START           Start time of record (e.g., 961005222917177)
BN_WIDTH        Data Bin Width
ETI             Extended TI counter

11.4.2 Attitude, Pointing, and Bit Rate

BIT_RATE        DP Bit Rate 0:H, 1:M, 2:L
ACS             ACS Status 0:fine mode, 1:corse mode
NSAS            NSAS cone angle (sun angle) (deg) (<0 during satellite night)
Z_ALPHA         R.A.(2000) of Z-Axis (deg)
Z_DELTA         Dec.(2000) of Z-Axis (deg)
EULER_3         3rd Euler Angle (Z-Y-Z)
SAT_ALT         Satellite altitude (km)
SAT_LON         Satellite longitude (deg)
SAT_LAT         Satellite lattitude (deg)
ELV             Target elevation from the Earth egde (deg)
COR             Cut Off Rigidity (GeV/c)
FOV             Field of Veiw  0:Sky/1:Night Earth/2:Day Earth
BR_EARTH        Angular distance from Bright Earth (deg)
SAA             In South Athrantic Anormaly?  1:yes/0:no
T_SAA           Time after SAA passage (s)
SUNSHINE        1:satellite is in daytime/ 0:night
T_DY_NT         Time after day/night transition (s)
ANG_DIST        Angular Distance of FOV from specified direction (deg)

11.4.3 SIS Status/ Monitors

Note n=0, 1 for SIS0 and SIS1 respectively, and m is the chip identification number.

Sn_MODE         SIS_n observation mode 0:Fnt/1:Brt/2:Fst/3:Frm
Sn_ID           SIS_n CCD ID LIST (e.g., 1111)
Sn_DSCR         SIS_n Discriminator status
SIS_ADRS        SIS Address Dscri 0:in 1:out for each chip
Sn_GRADE        SIS_n grade discriminate value (e.g., 127)
Sn_EVTRm        SIS_n Chip_m Event Threshold
Sn_SPTRm        SIS_n Chip_m Split Threshold
Sn_AE           SIS_n AE Status 0:normal/1:A-off/2:Power off
Sn_TEMP         SIS_n CCD temperature (deg C)
Sn_EVNTm        SIS_n chip_m HK Event number (counts/s)
Sn_PIXLm        SIS_n chip_m HK Pixel number over the threshold (couts/s)
Sn_TELMm        SIS_n chip_m telemely event number (couts/s)
Sn_SATFm        SIS_n chip_m saturation flag 0:no/ 1:yes
Sn_DFEm         SIS_n chip_m dark frame error (ADU)

11.4.4 GIS Status/ Monitors

Note n=2,3 means GIS2 and GIS3 respectively.

GIS_MODE        GIS observation mode, 0:PH/ 1:MPC/ 2:PCAL
GHVn_L          GIS HVLn status 16:off/ 8:reduction/ 0-7:level
GHVn_H          GIS HVHn status 16:off/ 8:reduction/ 0-7:level
Gn_LDHIT        GIS_n Lower Discri Hit counting rate (counts/s)
Gn_H0           GIS_n HK monitor H0 (counts/s)
Gn_H1           GIS_n HK monitor H1 (counts/s)
Gn_H2           GIS_n HK monitor H2 (counts/s)
Gn_L0           GIS_n HK monitor L0 (counts/s)
Gn_L1           GIS_n HK monitor L1 (counts/s)
Gn_L2           GIS_n HK monitor L2 (counts/s)
Gn_CPU_I        GIS_n HK monitor CPU_IN (counts/s)
Gn_CPU_O        GIS_n HK monitor CPU_OUT (counts/s)
Gn_TELM         GIS_n telemely event number (counts/s)
Gn_CPU_S        GIS_n CPU status, run +4, stop +2, error +1
GIS_HAMM        GIS Hamming Error 0:off/1:on
Gn_TEMP         GIS_n temperature (deg C)
Gn_HVHMN        GISn HV-H monitor (V)
Gn_HVLMN        GISn HV-L monitor (V)
Gn_HVHCM        GISn HV-H current monitor (uA)
Gn_DEADT        GIS_n Dead time correction factor (0-1)

11.4.5 Radiation Belt Monitor

RBM_TEMP        RBM temperature (deg C)
GIS_RBMF        RBM flag status of GIS 0:off/1:on
SIS_RBMF        RBM flag status of SIS 0:off/1:on
RBM_CONT        RBM counting rate (counts/s)

11.5 Important URLs

Here we list some important URLs mentioned in this document. They are listed in the alphabetical order of their `alias' names.

11.5.1 ASCA Getting Started Guide

11.5.2 ASCA GOF

11.5.3 ASCA GOF: Processing and Data Analysis

11.5.4 ASCA GOF: What's New

11.5.5 ASCANews

11.5.6 ASCA Observation Planning Guide

11.5.7 ASCA Science Data Processing

11.5.8 Background Normalization for Co-added Spectra

11.5.9 Calibration Uncertainties

11.5.10 FTOOLS

11.5.11 GIS Background

11.5.12 GIS3 CPU Trouble

11.5.13 GIS Gain Correction

11.5.14 GIS News

11.5.15 SIS News

11.5.16 XANADU

11.5.17 XIMAGE User's Guide

11.5.18 XRONOS User's Guide

11.5.19 XSELECT User's Guide

11.5.20 XSPEC User's Guide

next up previous contents
Next: About this document ... Up: ASCA ABC Guide Previous: 10. Spatial Analysis   Contents
Michael Arida 2002-10-22