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Seeing Triple
Swift in processingAfter more than three decades, scientists are still baffled by the violent, cosmic explosions of gamma rays that flash almost daily from random areas of the sky. Known as gamma-ray bursts, these brief yet brilliant events have long eluded scientific study. With its trio of scientific instruments, NASA's upcoming Swift mission promises to change all that.

Image to left: At Cape Canaveral Air Force Station in Florida, the Swift spacecraft waits for final removal of the protective cover (at top). See below for a description of each of Swift's three instruments. Credit: NASA/KSC

The Swift satellite's three telescopes work together to quickly pinpoint gamma-ray bursts and observe their afterglows. These telescopes cover a wide swath of the electromagnetic spectrum, targeting the bursts in the gamma-ray, X-ray, ultraviolet, and optical wavebands. Just 20 to 75 seconds after Swift's large field-of-view telescope detects one of these powerful explosions, the satellite will automatically turn, aiming its two narrow field-of-view telescopes at the burst. The afterglows will be monitored while they last. Mission data will be available to the public via the Internet as soon as they are processed.

Burst Alert Telescope (BAT):

With its large field-of-view and high sensitivity, the BAT will detect about 100 gamma-ray bursts per year. Once a burst is discovered, the BAT quickly calculates its position. The BAT also has a secondary science objective: an all-sky hard X-ray survey. As it watches the sky for a gamma-ray burst, it accumulates X-ray maps every five minutes. Over the telescope's lifetime, these images will result in an all-sky survey 20 times more sensitive than the last such survey, conducted in the late 1970s.

Artist concept of Swift instrumentsImage to right: Together, Swift's three scientific instruments will answer many questions about gamma-ray bursts and their afterglow. Credit: NASA/GSFC

X-ray Telescope (XRT):

The XRT will take images and measure light energy (spectra) during targeted observations of the afterglows that follow gamma-ray bursts. The images will be used to determine the burst's location with higher accuracy than initially found by the BAT. Scientists will use the spectral data to study the chemical elements that are produced in the explosion and to learn more about the environment in between us and the source of the burst.

Ultraviolet/Optical Telescope (UVOT):

Like the XRT, the UVOT will follow up on gamma-ray bursts by taking images and obtaining spectra of afterglows. The UVOT will also produce images of the explosions in visible and ultraviolet light, giving scientists more insight on the physics of the phenomena. The high-resolution UVOT images will also improve on the accuracy of the burst location measurements. The UVOT will also produce spectra that can be used to determine the distance to the source of this tremendous explosion.

For further information and technical details about each of the Swift science instruments, visit:
+ The Swift Instruments
+ Swift: Catching Gamma Ray Bursts on the Fly
Anna Heiney
NASA's John F. Kennedy Space Center