GINGALOG - Ginga LAC Log Catalog
The GINGALOG database table contains selected information from the Large Area
Counter (LAC) aboard the third Japanese X-ray astronomy satellite Ginga.
The Ginga experiment began on day 36, 5 February 1987 and ended in November
1991. Ginga consisted of the LAC, the all-sky monitor (ASM) and the
gamma-ray burst detector (GBD). The satellite was in a circular orbit at
31 degree inclination with apogee 670 km and perigee 510 km, and with a
period of 96 minutes.
A Ginga observation consisted of varying numbers of major frames which had
lengths of 4, 32, or 128 seconds, depending on the setting of the bitrate.
Each GINGALOG database entry is the first record of a series of observations
having the same values of `ACS MONITOR` (Attitude Control System). When
this value changes, a new FITS file was written. The other Ginga catalog
database, GINGAMODE is also a subset of the same LAC dump file used to
create GINGALOG. GINGAMODE contains a listing whenever any of the following
changes: `BITRATE`, `LACMODE`, `DISCRIMINATOR`, or `ACS MONITOR`. Thus,
GINGAMODE monitors changes in several parameters and GINGALOG is a basic
log of all the FITS files. Both databases point to the corresponding
archived Flexible Image Transport System (FITS) files, but GINGAMODE may
have more than one entry for a given FILE_LIGHTCURVE in the database.
The user is invited to browse though the observations available from GINGA
using GINGALOG or GINGAMODE, then extract the FITS files for more detailed
analysis. Type `dbhelp/dbname=gingalog` for more information.
The GINGAMODE LAC Catalog was prepared from data sent to NASA GSFC from
the Institute of Space and Astronautical Science (ISAS) in Japan. The
mission is described by Makino et al. (1987, Astrophys. Letters Commun.,
25, 223) and the instrument by Turner et al. (1989, Publ. Astron. Soc.
Japan, 41, 345). Some of the present documentation has been adapted from
The Large Area Counter (LAC) is the main instrument of Ginga. With the large
(4000 cm**2) effective area and low internal background, the LAC is the most
sensitive detector in the energy range 2-30 keV flown on board an orbiting
satellite to date. The LAC consists of eight identical proportional counters,
each co-aligned and with a 1 X 2 degree field of view (FWHM). It is capable of
measuring the energy spectrum of X-ray sources down to 0.2 mCrab level with a
nominal energy range from 1.5 to 37 keV. The fractional energy resolution at
6 keV is 18 percent (FWHM) and decreases in proportion to E**-0.5. The whole
energy range is divided into 64 energy channels of equal width.
This database points to Flexible Image Transport System (FITS) files
containing all the Large Area Counter data available at the HEASARC.
The FITS files contain low and high channel uncorrected count rates
for all LAC observations. These files are essentially lightcurves
created from the low and high counts. There are also GIF files for
many of the FITS files. There are no GIF files for those FITS files
that contain only one point, which represent less than 10% of the total
files. There are 11673 FITS files and 10584 GIF files for then entire
Time of the start of the first record of an observation. An observation
consists of those records in the GINGAMODE file that consecutively have the
same ACS (Attitude Control System) value.
Time of the stop of the last record of an observation.
The total length of time in this observation interval.
The on-time in this observation. A sum of the live times in this interval.
Designates the spacecraft mode during a particular ACS (Attitude Control
System) Mode. Settings include: NML (Normal), SL+ (Slewing positive),
SL- (Slewing negative), MAN (Maneuver), S36 (Slew through 360 degrees),
STB (STand By), LSP (Low SPin) and NAT (No ATtitude Solution).
The right ascension for this LAC observation.
The declination for this LAC observation.
The galactic longitude for this LAC observation.
The galactic latitude for this LAC observation.
The name of the spacecraft target. If the target was unknown or contained
multiple source, this value may be 'N/A' (not applicable). Some observations
contain more than one source because the ACS Monitor value remained constant
while the spacecraft changed targets.
The name for the FITS file corresponding to one entry in this database.
The FITS files have the form: GYYMMDD_HHMMSS_xz.FITS; G (for GINGA Large
Area Counter experiment); the year, month, day, hours, minutes, and
seconds of the start of the observation; x, which can be P for pointing,
meaning the entire file was 'on-target', S for slewing, or O for other,
meaning that standby or no attitude solution occurred in this file); z,
which can be 'C' for continuous BITRATE (the value for bitrate within
this file is the same for all rows, that is: the timebin size is constant,
either 4, 32 or 128 seconds) or 'M' for mixed BITRATE (this file contains
one or more bitrates, that is: this file contains rows that vary in length,
but the file also contains a TIMEDEL keyword and a FRACEXP (fractional
exposure) keyword to normalize the count rates. A typical GINGA FITS
file name would be G870305_120455_PC.FITS.
Questions regarding the GINGALOG database table can be addressed to the
HEASARC User Hotline.
If you have any problems, please consult the help
page or mail firstname.lastname@example.org