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.

Contents

1 Overview 1.1 Instruments 1.2 Science goals 2 Mission Progress 3 External links

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 concluded 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 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.
• On December 4 the power up of the on-board devices hit a snag, when the Thermo-Electric Cooler (TEC) for the X-ray CCD did not turn on as expected. Mission members are evaluating in what way the science data is influenced, if the TEC is off for the rest of the mission.
• December 17 at 7:28:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located on-board an apparent gamma-ray burst. The spacecraft did not autonomously slew to the burst since automated slewing is not yet enabled.
• Swift had its first GRB trigger during a period when the automatic slew as allowed. On January 17, 2005, at about 12:55 UT it pointed the XRT telescope to the on-board computed coordinates and observed a bright source in the field of view.
• On February 1, 2005 the mission team releases the "first light" picture of the UVOT instrument and declares Swift operational.
• As of April 7, 2005, Swift has detected about two dozen GRBs and X-ray afterglows for about 15 of them, and optical afterglows for a few. Optical afterglows are important for providing distance estimates.

External links

• NASA's Swift site
• Status page on the same site
• Gamma-ray Burst Real-time Sky Map based on Swift data
• Announcement of first Swift GRB
• GCN entry for first GRB observed with auto-slew
• APOD page with movie of separation from rocket

• New Scientist: Swift measures distance to gamma-ray bursts