The Ginga Mission

Ginga was launched on 1987 February 5 and remained operational until re-entry on 1991 November 1. The two X-ray detectors carried were a large area proportional counter (LAC) with approximately 4000 cm² collecting area (Makino 1987) and an all sky monitor (ASM). The LAC (Turner et al. 1989) was developed by ISAS in collaboration with the University of Leicester and the Rutherford Appleton Laboratory in the UK and the University of Tokyo and Nagoya University in Japan. The LAC consisted of eight identical proportional counters and covered the energy range of approximately 1.5 to 30 keV with a field of view of 1° x 2° (FWHM). Background rejection was obtained from several guard counters and anti-coincidence among individual LAC modules.

During operation the LAC observed approximately 350 targets. To date, over 190 papers in refereed journals have been written based on these observations. Notable highlights include the detection of X-rays from SN1987A, the discovery of six new pulsars, the identification of three new black hole candidates, discovery of cyclotron lines in the spectra of several pulsators, and astrophysically important spectral and timing information on a variety of active galaxies.

The ASM (Tsunemi et al. 1989) collected data typically once per day when Ginga executed a 360° rotation. Long term light curves for a large number of bright X-ray sources were thus produced. However, our project does not include the archiving of these data.

The Ginga data set totals 40 GB. To date, the principal means of access by US astronomers has been the Sirius database system, available only at ISAS. A few investigators from outside Japan and the UK have made use of the Ginga data, but this has been limited by the general requirement that U.S. scientists, for example, must undertake the majority of their data reduction in Japan. The Ginga data sets provide an opportunity to cross-compare with data from other satellites, but due to the accessibility difficulties, the existing data have not yet been fully exploited.