Advanced Satellite for Cosmology & Astrophysics ASCA, formerly named Astro-D, was a high throughput spectroscopic observatory. It was Japan's fourth cosmic X-ray mission, targeting the x-ray background, active galactic nuclei, galactic clusters, supernovae, and their remnants. Part of the scientific payload was provided by the United States. After 8 months of instrument validation, ASCA became a guest observer project, with astronomers from Japan, the US, and members states of the European Space Agency having access to the program. This was the first satellite to use CCDs for X-ray astronomy. Spacecraft: Solar arrays provided 601 W BOL/489 W after 3 yr. , two 19 Ahr NiCd batteries. Attitude control <1 arcmin, determination <0.3arcmin; 3 axis control by 4 reaction wheels. Data from bubble memory recorder (134 Mb) downlinked on X-band at 264 kbit/sec. The tubular telescoping optical truss was constructed of carbon fibre which was folded for launch, and was extended by a sliding mechanism after reaching orbit. Payload: Four x-ray telescopes, consisting of four sets of coaxially aligned multilayer thin foil mirrors provided by GSFC. At the focus of two of the telescopes was a Gas Imaging Spectrophotometer (GIS) consisting of two gas imaging scintillation proportional counters covering 0.7-10 keV. The second focal plane instrument was a solid-state imaging spectrometer with two CCDs covering 0.5-8 keV.

Design Life: 5 years. Total Length: 4.0 m. Maximum Diameter: 1.2 m. Electric system: 0.39 total average kW. Electrical System: Solar array.

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