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, early known as Astro-D, 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.
The spacecraft's solar arrays provided 601 W BOL / 489 W after 3 years and recharged two 19 Ahr NiCd batteries. Attitude control to <1 arcmin, determination <0.3arcmin by 3 axis control by 4 reaction wheels. Data from a bubble memory recorder (134 Mb) was downlinked on X-band at 264 kbit/sec. The tubular telescoping optical truss was constructed of carbon fiber which was folded for launch, and was extended by a sliding mechanism after reaching orbit.
The payload consisted of 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.
Electric System: 0.389 average kW.
Height: 4.00 m (13.10 ft).