The Chandra X-ray Observatory is the U.S. follow-on to the Einstein
Observatory. Chandra was formerly known as AXAF, the Advanced X-ray
Astrophysics Facility, but renamed by NASA in December, 1998.
Originally three instruments and a high-resolution mirror carried in
one spacecraft, the project was reworked in 1992 and 1993. The Chandra
spacecraft carries a high resolution mirror, two imaging detectors,
and two sets of transmission gratings. Important Chandra features are:
an order of magnitude improvement in spatial resolution, good
sensitivity from 0.1 to 10 keV, and the capability for high spectral
resolution observations over most of this range.
The First Byurakan Survey (FBS) is the largest and the first systematic objective prism survey of the extragalactic sky. It covers 17,000 sq.deg. in the Northern sky together with a high galactic latitudes region in the Southern sky. The FBS has been carried out by B.E. Markarian, V.A. Lipovetski and J.A. Stepanian in 1965-1980 with the Byurakan Observatory 102/132/213 cm (40"/52"/84") Schmidt telescope using 1.5 deg. prism. Each FBS plate contains low-dispersion spectra of some 15,000-20,000 objects; the whole survey consists of about 20,000,000 objects.