Swift Gamma-Ray Burst Mission
The Swift Gamma-Ray Burst Mission consists of an unmanned spacecraft called Swift, which was launched into orbit on November 20, 2004, at 17:16:00 UTC (12:16 PM, EST) on top of a Delta 2 rocket. It is managed by NASA's Goddard Space Flight Center.
Overview
Swift is a multi-wavelength space-based observatory dedicated to the study of gamma-ray burst (GRB) science. Its three instruments will work together to observe GRBs and afterglows in the gamma-ray, X-ray, ultraviolet, and optical wavebands. This mission is part of NASA's "Medium Explorer program" and the satellite was developed by an international consortium from the United States, United Kingdom, and Italy.
During its nominal mission of two years about 200 GRBs should be observed, and as with many other NASA missions, once the two years are conluded successfully the mission will probably be extended. A dedicated telescope will be used to locate the position of each event with an accuracy of 1 to 4 arc-minutes within 15 seconds. The satellite is then able to reorient itself automatically in about 20 to 75 seconds to point all of its instruments at the burst location. This ability is the reason for the mission's name "Swift." In order to achieve this fast slew rate, the observatory is equipped with momentum wheels as part of its reaction control system. These wheels are more massive than any used on past known spacecraft, and are therefore more effective at reorienting the spacecraft when they spin.
In the time between GRB events the instruments on board will conduct an all sky survey in the hard X-ray. After its successful completion, it is anticipated to yield new black hole candidates in the sky.
Instruments
There are three observing instruments on board:
- Burst Alert Telescope (BAT), 15 - 150 keV energy range. It initially detects a new GRB event and computes its coordinates in the sky.
- X-Ray Telescope (XRT), 0.3 - 3 keV energy range. It can take images and perform spectral analyses of the GRB afterglow. This data will provide a more precise location of the GRB and the red-shift of the source.
- UV/Optical Teslescope (UVOT), 170 - 650 nm wavelength range. This instrument will also provide images and spectra. It will be used for follow-up observation of the GRB.
Science goals
This mission has multiple science goals:
- Determine the origin of GRBs. There seem to be at least two types of GRBs, only one of them can be explained with the a hypernova, creating a gamma-ray beam. More data is needed to explore other explanations.
- GRBs seem to take place at "cosmological distances," which means they can be used to probe the distant, and therefore young, universe.
- The all-sky survey is more sensitive than any previous one, and will add significantly to our knowlegde of astronomical X-ray sources. Thus, it could also yield unexpected results.
Mission Progress
- Swift was launched on November 20, 2004, and reached its design orbit at 584x601 km.
External links
- NASA's Swift site (http://swift.gsfc.nasa.gov)
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