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Description of the ASCA Mission

The data in this archive were obtained by the X-ray detectors on board the ASCA X-ray satellite observatory. ASCA (formerly named Astro-D) is Japan's fourth cosmic X-ray astronomy mission and was successfully launched on February 20, 1993. The first eight months of the ASCA mission were devoted to performance verification, after which the project changed to a general/guest observer program for the remainder of the mission. In this phase the observing program is open to astronomers based at Japanese and US institutions, as well as those who are located in member states of the European Space Agency.

ASCA Mirrors ASCA carries four large-area X-ray telescopes. At the focus of two of the telescopes are Gas Imaging Spectrometers (GIS), while Solid-state Imaging Spectrometers (SIS) are at the foci of the other two telescopes. The X-ray Telescopes (XRTs) utilise multiple-nested, thin-foil, conical mirrors and provide a spatial resolution of 1.5 arcmin (half power radius) and a broad bandpass of 0.1-10 keV.
The two SIS detectors (0.4-10.0 keV) are identical Charge-Coupled Device (CCD) cameras with a maximum field of view (FOV) of 22 x 22 arcminutes, and are the first X-ray CCD spectrometers in orbit. ASCA SIS
ASCA Mirrors The GIS (0.8-10.0 keV) is a gas imaging scintillation proportional counter and is based on the GSPC that flew on the second Japanese X-ray astronomy mission TENMA. The GIS instruments complement the SIS: above the Xenon L edge (~ 5 keV), the GIS has a detector efficiency that is both greater than SIS and falls off less rapidly. The GIS, with a circular FOV of radius 25 arcminutes, observes about 4 times the area covered by the SIS.
Data obtained by ASCA are processed at GSFC for distribution to principal investigators. The ASCA data archive resides at GSFC for access by the general public with copies also available at ISAS and LEDAS.

This database contains the event files and housekeeping data obtained from the ASCA GIS and SIS instruments for each pointed observation and have been generated with the REV2 processing.

The data are stored in the standard FITS (Flexible Image Transport System) format and also as GIF (Graphic Interchange Format) files. All FITS files are compressed using the gzip compress utility. The processing log files are in HTML (HyperText Markup Language) format.

ASCA Image

"The X-ray astronomy satellite ASCA" (Tanaka, Y., Inoue, H. & Holt, S., 1994, PASJ, 46, L37)