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ASCAPUBLIC: Help

==> ascapublic.html <==

ASCAPUBLIC: ASCA Archive Public Contents List


Overview

This table contains a record of data from the ASCA mission that is available from the HEASARC archive. The listing includes future data which may not yet be in the public domain. The following proprietary periods apply to the ASCA data:
---
 * PV data taken between April 1993 and approximately December 1993 is made 
    public 18 months from the observation date.

 * US and joint US/Jp data (i.e., with a US PPI) that was delivered prior 
    May 2, 1994, will be public 1 year after that date. 

 * US and joint US/Jp data delivered after May 16, 1994, will be public 
    1 year + 2 weeks from dispatch to the PI.

 * Jp and joint Jp/US data (with a Japanese PPI) will be delivered 
    18 months + 2 weeks from dispatch to the PI.
---
The data is this table is automatically updated on a weekly basis each Wednesday.

Intrepid explorers of the ASCA public archive should note that the PV data, especially the data taken in the first few months, is not always optimized for scientific investigation of the targeted object. Many observation were made for instrument calibration and contain frequent mode changes and non-standard parameter setting for which instrument responses are not available. The observation modes and instrument setting during the latter PV and AO phase are more stable. If in doubt, please ask the ASCA GOF.


Parameters

Seq_ID
  A unique identifier for each ASCA observation sequence.
Name
  The field name, as specified by the observer.
RA
  The Right Ascension of the target.
Dec
  The Declination of the target.
LII
  The galactic latitude.
BII
  The galactic longitude.
File_Name
  The file name(s) of the original frf telemetry files as generated by
  ISAS. There may be one or more of these files per sequence. The filenames
  take the form: `ft930511_0321.1437` which is the yrmndy_hrmn.hrmn giving the
  start and stop time of the observation.
Time
  The start time of the observation.
End_Time
  The end time of the observation.
GIS_Ontime
  The total time the GIS instrument was turned on. This is NOT the good
  exposure time.
SIS_Ontime
  The total time the SIS instrument was turned on. This is NOT the good
  exposure time.
PI
  The name of the principal investigator.
Prop_Type
  The type of object that was observed.
Prop_Number
  The number of the proposal.
Target_Number
  The target number within the proposal.
Public_Date
  The data when the sequence enters the public domain, given in
  year-month-day format.
Class
  The BROWSE object class. 

File Structure

ASCA data is most conveniently stored (and labeled) by the 8-digit SEQUENCE-NUMBER which is assignrd to each pointed observation and generally consists of a day's worth of consecutive data.
The data for a particular observation sequence is quite large (up to 200 MBytes or more) and thus the data is divided into six manageable sub-directories (TELEM, AUX, RAW, SCREENED, UNSCREENED, and PRODUCT). For a typical analysis, not all files are necessary. The following is summary of each sub-directory and what is needed for a typical analysis:

---
 * TELEM: Contains the telemetry (FRF) files which make up each sequence.
(typically one file, occasionally more). These are by far the largest files
and these data are NOT required; they are here for completeness.
         
 * RAW: Contains the fundamental FITS format event list files, with one file per
mode change per instrument. These are the basic data, which are required for a
complete analysis of the data. You'll want this if you plan to start the
analysis from scratch, using ascascreen and tkascascreen. But before
downloading this relatively large number of files, its wise to take a quick
look at one of the processed products. 

 * AUX: Contains the calibration and filter files. The filter files (extension
.mkf) are necessary to time filtering the data. To make any rescreening of the
data the .mkf file must be retrieved. For barycentric timing correction the
frf.orbit file is required. The other files contain calibration information
used during the processing and are typically not required for a standard
analysis.

 * UNSCREENED: Contains the modally merged event list files for each
instrument, but not screened to remove bad data (no time filter). This is a
convenient starting point for basic data analysis, especially if you want to
rescreen the data using different cleaning criteria.

 * SCREENED: Contains the modally merged event list files - screened using
current standard filter criteria. These files are useful for quick analysis to
extract standard spectra, images, and, light curves.
    
 * PRODUCTS: contains the product catalog, information, and contents files. A
good getting started point with basic observation catalogue information,
pre-digested quick look images, and summary plots. 
---
The individual files for all four instruments (SIS0 + SIS1 + GIS2 + GIS3), for a given observation sequence, are stored together under [seq #]/[sub_dir]. This structure is automatically recognized by the XSELECT v1.2 and higher. It is recommended that this directory structure be duplicated at the home institution. Most of the files have been compressed (*.Z extension) using the UNIX compress utility for ease of storage and transfer and should be uncompressed before starting an XSELECT session.
The individual ASCA data files are archived in FITS format and the following two basic naming conventions are used to identify them:
----------------------------------------------------------------------------

a) The Telemetry FRF (First Reduction Files) convention:
  
 root:  ft930408_0413_0603 = ft[OBS-DATE]_[START(UT)]_[STOP(UT)]
 
b)  AD (Modally merged files):
                      
 root:          ad10004010 = ad[SEQUENCE-NUMBER]

c) Appendage (added on for both a and b):

                  s100312h = [s1] [003] [12] [h] 

                           = [instrument]  [index] [inst. mode] [bitrate]

                           = [s0/s1/g2/g3] [0-999]    [code]     [l/m/h]
                                                        ||
       Some common modes:                         01 = SIS FAINT
                                                  02 = SIS BRIGHT
                                                  03 = SIS FAST
                                                  70 = GIS PH 
----------------------------------------------------------------------------
For the FT files, the index parameter orders the files by time. The AD files are indexed by number of events; for a given set, files with the lowest numbers have the largest number of events.
The following extensions are commonly used to denote different types of files:
---
 * .fits indicate raw FITS files containing photon event data. 

 * .unf are unscreened FITS events files.

 * .evt are screened FITS events files.

 * .img are FITS images in sky coordinates.

 * .detimg are FITS images in detector coordinates.

 * .gif are gif format images. The file names are appended with _detimg or
  _img to indicate if the images are sky or detector coordinates.

 * .mkf are the "makefilter" filter files, used to screen the data.

 * .txt contain ASCII files.

 * .log are the output from the processing logs.

 * .ps are postscript output from the quicklook analysis.

 * .cat are the observation catalogues, which list all the modes
  and detector configurations. These can be used via XSELECT to choose
  the files of interest.
---

References

A full description of the ASCA archive and how to use it can be found under the WWW at `http://heasarc.gsfc.nasa.gov/docs/asca/archive.html`, or in the FTP account at `legacy.gsfc.nasa.gov` in the document `asca/doc/archive.txt`.

Contact Person

If you have questions regarding the ASCAPUBLIC database table or the ASCA archive, contact the ASCA help desk.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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