Mission Overview

The Broad Band X-ray Telescope (BBXRT) was the first focusing X-ray telescope to operate over a broad energy range (0.3-12 keV) with moderate energy resolution. BBXRT was added to the Astro-1 mission, to take advantage of the unique opportunity provided by the bright supernova called SN1987A. The energy resolution (90 eV and 150 eV at 1 and 6 keV, respectively), 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. It was not flown again on the Astro-2 mission.

The BBXRT consists of a pair of coaligned thin foil conical X-ray mirrors, with a cryogenically-cooled, Si(Li) spectrometer at the focus of each. The X-ray mirrors have a focal length of 3.8 m and a diameter of 40 cm. Each mirror consists of 118 nested pairs of reflectors. Each reflector consists of 0.017 mm thick aluminum shaped into a cone, coated with an acrylic lacquer to form a microscopically smooth surface, which is overcoated with gold to enhance X-ray reflectivity. The spatial resolution of the telescope is 1.3 arcmin (half power radius) and the plate scale is 0.91 arcmin per cm. The detectors are segmented into five discrete Si(Li) detection elements, each with 512 energy channels. The circular central element has a diameter (field of view) of 4.0 arc minutes. The outer ring extends the field of view to 17 arcminutes, and is divided into four 90 degree segments. Each is located in a cryogenically-cooled vacuum cryostat. Attached to each cryostat is a solid argon cooler with a 90 lb capacity.

BBXRT's observing efficiency was reduced due to problems in the spacecraft's pointing systems. However, BBXRT still achieved a total of 157 observations of 82 X-ray sources.

Lifetime: December 2 1990 - December 11 1990
Energy Range: 0.3 - 12 keV
Launch Information
Launch Date: 1990-12-02 at 06:49:01 UTC
Launch Vehicle: Shuttle
Launch Site: Cape Canaveral, United States
Decay Date: 1990-12-10

Trajectory Description
Type: Orbiter
Central Body: Earth
Epoch start: 1990-12-02 06:49:01 UTC
Orbital Parameters
Periapsis 500.0 km
Apoapsis 500.0 km
Period 94.0 minutes
Inclination 28.0°
Eccentricity 0.0

Instrumentation

Payload:

Two Co-Aligned Telescopes each with a segmented Si(Li) solid state spectrometer (detector A and B) composite of five pixels.
Total FOV 17.4 ´ diameter, Central pixel FOV 4 ´ diameter
Total area 765 cm2 at 1.5 keV, and 300 cm2 at 7 keV

Science

• Resolved iron K line in the binaries Cen X-3 and Cyg X-2
• Detect evidence of line broadening in NGC 4151
• Study of cooling flow in clusters

Summary