ASCA (Advanced Satellite for Cosmology and Astrophysics; formerly Astro-D) is Japan's fourth x-ray astronomy mission and the second for which the U.S. is providing a significant part of the scientific payload. Its four large-area telescopes focus x-rays from a wide energy range onto a pair each of x-ray sensitive Charge-Coupled Devices (CCD's) and imaging Gas Scintillation Proportional Counters (GSPC's). ASCA is examining a variety of x-ray sources with moderate spatial resolution and spectral resolution, with particular emphasis on the iron K band.
Quoted from the PDMP:
The two identical x-ray CCD cameras on board ASCA are known as the Solid-state Imaging Spectrometers (SIS) and were provided by a hardware team from the Massachusetts Institute of Technology (MIT), Osaka University, and Japan's Institute of Space and Astronautical Science (ISAS). Each CCD camera head is based around four $420 \times 422$ pixel MIT Lincoln Laboratory CCD chips abutted side by side, with four preamplifiers, front-side illuminated. The field of view of each camera is $22 \times 22$ arcminutes. Since the SIS is the first x-ray CCD spectrometer on orbit, its resistance to radiation damage will be fully established as the mission progresses.
Each Gas Imaging Spectrometer (GIS) is a Xenon-filled imaging gas scintillation proportional counter; these two instruments were provided by the University of Tokyo and ISAS. The GIS complements the SIS: above the Xenon L edge ($\approx 5$ keV), the GIS has a detection efficiency that is both greater than the SIS and falls off less rapidly. The GIS, with a circular field of view of radius 25 arcminutes, observes about 4 times the area than covered by the SIS.
The high throughput X-Ray Telescopes (XRT's) utilize multiply-nested, thin foil, conical mirrors. The XRT's were supplied by GSFC, Nagoya University and ISAS, and provide a spatial resolution of $\sim$ 1.5 arc minutes (half-power radius) and a broad bandpass, 0.1-10 keV.
ASCA is the first x-ray imaging mission operating between 0.5 and 12 keV with high energy resolution (8 and 2 percent at 5.9 keV for the GSPC's and CCD's, respectively). It observes typically one or two sources per day. These combined capabilities enable a diverse and exciting program of astronomical research.
HEASARC User Hotline.