This Legacy journal article was published in Volume 1, May 1992, and has not been
updated since publication. Please use the search facility above to find regularly-updated
information about this topic elsewhere on the HEASARC site.
New Ginga Catalogs
Two recent additions to the HEASARC database come from the Japanese X-ray
satellite, Ginga, formerly known as ASTRO-C. These new catalogs, Gingalog and
Gingamode, have been created from the Large Area Counter (LAC) experiment data
files and are available to on-line users of the HEASARC database via the
BROWSE software. The LAC was the main instrument aboard GINGA and its 4000
cm2 detector up to now has been one of the most sensitive in the
energy range from 2-30 keV. It was capable of measuring the energy spectrum of
X-ray sources down to 0.2 millicrab and it operated successfully from 5
February 1987 until 1 November 1991.
The LAC data files are records of all the LAC observations and contain
uncorrected broad band count rates in one of three telemetry time intervals.
Thus, the instrument's 48 pulse height channels were summed into two
channels that were written into the LAC data files as LACLOW and LACHIGH. These
energy channel values were then written out in ASCII records either every 4,
32, or 128 seconds depending on the instrument's telemetry bitrate, which can
be high, medium, or low respectively. These ASCII records were then read into
two separate catalogs within the HEASARC metabase and into FITS files. The new
catalogs can be accessed to ascertain what archival Ginga data exists. Anyone
wishing to analyze or gain access to the background-subtracted, higher time
resolution data must contact Dr. F. Makino at ISAS in Japan. This article
describes how the HEASARC catalogs Gingalog and Gingamode were created from the
LAC data files.
The large LAC data files were divided into two catalogs that only indicated
when changes occurred in the LAC data file records. In Gingalog, each time one
of the parameters, the Attitude Control System Monitor (ACS Monitor), changed
from its previous value, a new entry was written to the Gingalog catalog.
Since Gingalog was meant only as a log, only certain parameters from the
original LAC data file were written to the catalog. These parameters include:
RA and DEC
LII and BII
Start and Stop time
Z Axis RA and Z Axis DEC
The ACS Monitor parameter was selected because it defines the spacecraft
pointing mode, and has values of:
SL+ slewing positive
SL- slewing negative
S36 slew through 360 degrees
LSP low spin
The Gingamode catalog is a log of each change in the instrument mode.
Gingamode was also created by reading the LAC data file and a new entry to
Gingamode was written when any of the BITRATE, LAC MODE, ACS MONITOR or
DISCRIMINATORS parameters changed. Unlike Gingalog, Gingamode contains all the
same parameters as the original LAC data files so it has all the parameters
that Gingalog has, plus those in the FITS files mentioned above.
Since Gingalog contains only records when the ACS Monitor value changed, those
records occurring between changes were written into FITS format data files
stored on an NDADS optical WORM platter. There is one FITS file per entry in
Gingalog. They are also accessible using BROWSE when Gingalog is loaded. They
can be plotted by the PLOTFITS command or extract using the FSTAGE and
xp commands. The first record in one of the FITS files will also be
an entry in the Gingalog catalog, and the remaining records will be all the
original LAC data file records after that one having the same ACS Monitor
value. Since the records within the original LAC data files were separated by
either 4, 32 or 128 seconds depending on the bitrate, the time resolution
within a FITS file will vary because the start time of a record will only be
known to one of the above three accuracies. The FITS files also contain all
the parameters from the original LAC data files not included in the Gingalog
entries. These parameters include:
BITRATE rate of telemetered data
LAC MODE spacecraft data mode
DISCRIMINATORS setting of the three discriminators
SKYVIEW spacecraft viewing mode
SUPER FRAME NUMBER major frame within an observation
LOW COUNT RATE lower channels count rate
HIGH COUNT RATE higher channels count rate
SUD COUNT RATE surplus over the upper level discriminator
PIM COUNT RATE payload instrument monitor count rate
MAGNETIC RIGIDITY earth's magnetic field rigidity
TRANSMISSION collimator efficiency
The on-line user can view the entries in Gingalog, and if there is a section of
data that the user would like to scrutinize further, the FITS file
corresponding to that section can be accessed and analyzed. Thus the user has
access to all the data without the time consuming search by BROWSE through the
millions of records in the original LAC dump files.
Both catalogs point to FITS files. Each Gingalog entry will have one FITS file
but there can be several Gingamode entries corresponding to each FITS file
because a new FITS file will only be created when the ACS Monitor value
changes. Thus, either catalog can be scanned for changes in count rates or
other parameters and any entry that looks interesting can be further studied by
accessing the corresponding FITS file and seeing all the observation frames
that succeeded it. The FITS file name corresponding to each Gingalog or
Gingamode entry is shown in the LAC FILE parameter listed in either catalog.
Questions and comments concerning these catalogs, or requests for individual
FITS files can be addressed to Brendan Perry (HEASRC::PERRY) or Charles Day
An example of BROWSE sessions with Gingalog and Gingamode appears on the
Gingalog and Gingamode Examples from BROWSE
HEASARC> browse gingalog
Loading GINGALOG database sample TOTAL indexed on DEC
Ginga LAC Log Catalog
GINGALOG_TOTAL_DEC > sc Search in a cone of selected
R.A. (1950 d/f= 5 h 36 m 19.20sec): 5 30 radius centered on selected
Dec (1950 d/f=-72 deg 34 m 12.00sec): -68 00 coordinates.
Radius in arcmin. (d/f= 60.00):45.00
GINGALOG_TOTAL_DEC > dsam Display the database parameters
on one line.
GINGALOG_TOTAL_DEC > dall Display all the parameters of
Enter start entry number [d/f=1]: 1 selected entries.
Enter end entry number [d/f=1]:
GINGALOG_TOTAL_DEC > dcoord Display name and coordinates
Enter start entry number [d/f=1]:3 of selected entries
Enter end entry number [d/f=1]:8
GINGALOG_TOTAL_DEC > cdb Change databases to Gingamode.
Database name: gingamode
Loading GINGAMODE database sample TOTAL indexed on DEC
Ginga LAC Mode Catalog
GINGAMOD_TOTAL_DEC > sc Search in a cone of selected
R.A. (1950 d/f= 5 h 30 m 00.00sec): 5 30 radius centered on selected
Dec (1950 d/f=-68 deg 00 m 00.00sec): -68 00 coordinates.
Radius in arcmin. (d/f= 60.00):45.00
GINGAMOD_TOTAL_DEC > dsam Display the database parameters
on one line.
GINGAMOD_TOTAL_DEC 6> exit Exit BROWSE.
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