GINGALOG - Ginga LAC Log Catalog

Overview

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_LCURVE 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.

References

"New Ginga Catalogs", by B. Perry, Legacy, #1, May 1992.

The Ginga 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 these papers.

Provenance

The Ginga LAC Log Catalog was prepared from data sent to NASA/GSFC from the Institute of Space and Astronautical Science (ISAS) in Japan.

Description

The Large Area Counter (LAC) was the main instrument of Ginga. With the large (4000 cm²) effective area and low internal background, the LAC was 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 was 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.

Data Products

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 mission.

Parameters

Time
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.

End_Time
Time of the stop of the last record of an observation.

Telapse
The total length of time in this observation interval.

Exposure
The on-time in this observation. A sum of the live times in this interval.

ACS_Monitor
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).

RA
The right ascension for this LAC observation.

Dec
The declination for this LAC observation.

LII
The galactic longitude for this LAC observation.

BII
The galactic latitude for this LAC observation.

Name
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.

File_Lcurve
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.

Contact Person

Questions regarding the GINGALOG database table can be addressed to the HEASARC Help Desk.

Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:28:01 EDT