Editing Neil Gehrels Swift Observatory (section)

=== Burst Alert Telescope (BAT) ===
[[File:Swift's instrument - diagram of Burst Alert Telescope (BAT).jpg|thumb|Diagram of Burst Alert Telescope]]
The BAT detects GRB events and computes its coordinates in the sky. It covers a large fraction of the sky (over one [[steradian]] fully coded, three steradians partially coded; by comparison, the full sky solid angle is [[Solid angle|4π]] or about 12.6 steradians). It locates the position of each event with an accuracy of 1 to 4 [[Minute and second of arc|arcminutes]] within 15 [[second]]s. This crude position is immediately relayed to the ground, and some wide-field, rapid-slew ground-based telescopes can catch the GRB with this information. The BAT uses a [[coded aperture|coded-aperture mask]] of 52,000 randomly placed {{cvt|5|mm}} [[lead]] tiles, {{cvt|1|m}} above a detector plane of 32,768 {{cvt|4|mm}} [[Cadmium zinc telluride]] (CdZnTe) hard X-ray detector tiles; it is purpose-built for Swift. Energy range: 15–150 [[Electronvolt|keV]].<ref>{{cite web|url=http://swift.gsfc.nasa.gov/docs/swift/about_swift/bat_desc.html|title=Swift's Burst Alert Telescope (BAT)|publisher=NASA|date=February 28, 2006|access-date=May 2, 2009}} {{PD-notice}}</ref>