AXAF

The Advanced X-ray Astrophysics Facility, originally intended by NASA to follow the Hubble Space Telescope as a long-lived X-ray observatory for the 1990s, with in-orbit servicing from the space shuttle. A direct successor to the Einstein Observatory, AXAF was to carry an array of large (1.2-meter outer diameter) coaxial grazing incidence mirrors in a nested configuration, high-resolution cameras using both CCDs and microchannel plates, and a cryogenically cooled X-ray spectrometer. Budgetary constraints led in 1992 to the restructuring of the AXAF into two smaller missions, AXAF-I (concerned with high-resolution X-ray imaging) and AXAF-S (dealing with X-ray spectroscopy). AXAF-I was scheduled for launch in 1998/99 into a highly eccentric orbit that would keep it out of the Earth's shadow for long periods, thereby maximizing its observation time. AXAF-S was to follow it into space in 1999, traveling in a near-Earth Sun-synchronous orbit to conduct high-resolution X-ray spectroscopy with no in-orbit servicing. In the event, NASA canceled AXAF-S, and its advanced X-ray spectroscopic instruments were transferred to the ill-fated Japanese Astro-E mission (see Astro-E2). Development of AXAF-I continued, however, and it was eventually successfully launched in July 1999 and renamed Chandra (see Chandra X-ray Observatory).