The Broad Band X-ray Telescope (BBXRT) was flown on the space shuttle Columbia (STS-35) on 1990 December 2-December 11, as part of the ASTRO-1 payload. The flight of BBXRT marked the first opportunity for performing X-ray observations over a broad energy range (0.3-12 keV) with a moderate energy resolution (typically 90 eV and 150 eV at 1 and 6 keV, respectively).
This energy resolution, coupled with an extremely low detector background, made BBXRT a very powerful tool for the study of continuum and line emission from cosmic sources. The observing program was designed to be an even mix of Galactic and extragalactic targets, although the Galactic Center region was not available due to the time of year that BBXRT was launched.
Source: wikipedia, NASA