| Institution: | (1) Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Greenbelt, MD, 20771;(2) National Research Council, 2101 Constitution Avenue, NW, Washington, DC, 20418;(3) Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM, 87545;(4) Department of Astronomy, University of Maryland, College Park, MD, 20742-2421;(5) Universities Space Research Association, 10227 Wincopin Circle, Suite 212, Columbia, MD, 21044;(6) Institute of Space and Astrononautical Science, 3-1-1, Yoshinodai, Sagamihara, 229-8510 Kanagawa, Japan;(7) Department of Physics, University of Tokyo, Hongo 7-3-1, Bunkyo-ku, 113, Tokyo, Japan |
| Abstract: | he burst alert telescope (BAT) is one of three instruments on the
Swift MIDEX spacecraft to study gamma-ray bursts (GRBs). The BAT first detects the GRB and localizes the burst direction to an
accuracy of 1–4 arcmin within 20 s after the start of the event. The GRB trigger initiates an autonomous spacecraft slew to
point the two narrow field-of-view (FOV) instruments at the burst location within 20–70 s so to make follow-up X-ray and optical
observations. The BAT is a wide-FOV, coded-aperture instrument with a CdZnTe detector plane. The detector plane is composed
of 32,768 pieces of CdZnTe (4×4×2 mm), and the coded-aperture mask is composed of ∼52,000 pieces of lead (5×5×1 mm) with a
1-m separation between mask and detector plane. The BAT operates over the 15–150 keV energy range with ∼7 keV resolution,
a sensitivity of ∼10−8 erg s−1 cm−2, and a 1.4 sr (half-coded) FOV. We expect to detect > 100 GRBs/year for a 2-year mission. The BAT also performs an all-sky
hard X-ray survey with a sensitivity of ∼2 m Crab (systematic limit) and it serves as a hard X-ray transient monitor. |
