In-flight performance of the Broad-Band X-Ray Telescope

The Broad-Band X-Ray Telescope (BBXRT) was designed to carry out moderate resolution spectrophotometry of cosmic X-ray sources in the 0.3-12 keV band from the Space Shuttle. It consists of a pair of coaligned conical foil telescopes, with cryogenically cooled Si(Li) spectrometers as focal instruments. It was flown as part of the Astro-1 mission in December, 1990. The in-flight performance of the instrument was essentially as predicted on the basis of ground calibration and modelling. We discuss the performance of the system, with emphasis on the conical mirror systems, and present some preliminary scientific results which illustrate the power of broad band, high sensitivity X-ray spectrophotometry.