Gamma-ray Large Area Space Telescope

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This article or section contains information regarding a future spaceflight.
Due to the nature of the content, details may change dramatically as the launch date approaches and/or more information becomes available.

The Gamma-ray Large Area Space Telescope, or GLAST, is a future space-based gamma-ray telescope, designed to explore the high-energy Universe. It will study astrophysical and cosmological phenomena such as active galactic nuclei, pulsars, other high-energy sources, and dark matter.

GLAST is a joint venture of NASA and the United States Department of Energy, which also includes strong international support. It is currently scheduled to launch on October 7, 2007^[1] on a Delta-7920H-10C rocket.

GLAST will carry two scientific instruments, the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM). The LAT is an imaging gamma-ray detector which will be sensitive to photons with energy from about 30 million electron volts (MeV) to 300 billion electron volts (GeV). The GBM consists of 14 scintillation detectors which will detect bursts of photons from 5 thousand electron volts (keV) to 25 MeV.

The instruments will be carried by a spacecraft made by General Dynamics Advanced Information Systems (formerly Spectrum Astro) in Gilbert, Arizona. It will travel in a low, circular orbit with a period of about 95 minutes. Its normal mode of operation will maintain its orientation so that the instruments are always looking away from the earth, with a "rocking" motion to equalize the coverage of the sky. Thus their view will sweep out across most of the sky about 16 times per day. It will also be possible to maintain an orientation that points to a chosen target which deserves extra attention.

Artist's conception of the GLAST satellite

The LAT detects individual gamma rays using technology similar to that used in terrestrial particle accelerators. Photons hit thin metal sheets, converting to electron-positron pairs. These charged particles pass through interleaved layers of silicon microstrips, causing ionization which can be detected as tiny pulses of electric charge. Information from several layers of this tracker can be combined to determine the path of the particles. After passing through the tracker, the particles enter the calorimeter, which consists of a stack of cesium iodide scintillator crystals to measure the total energy of the particles. The LAT's field of view is large, about 20% of the sky. The resolution of its images is modest by astronomical standards, a few arc minutes for the highest-energy photons and about 3 degrees at 100 MeV. The LAT may be considered a bigger and better successor to the EGRET instrument on NASA's Compton Gamma Ray Observatory satellite in the 1990's. The components of the LAT were produced in by several institutions in several countries, then assembled at the Stanford Linear Accelerator Center (SLAC).

The GBM detects sudden flares of gamma rays produced by gamma ray bursts and solar flares. Its scintillators are positioned on the sides of the spacecraft to view all of the sky which is not blocked by the earth. The design is optimized for good resolution in time and photon energy. The GBM is a cooperative project of NASA's Marshall Space Flight Center and Germany's Max Planck Institut für Extraterrestrische Physik.

Both instruments have finished their construction and have undergone environmental testing, being subjected to vibration, vacuum, and high and low temperatures to ensure that they can withstand the stresses of launch and continue to operate in space. They are currently integrated with the spacecraft at the General Dynamics facility in Gilbert, Arizona. The complete observatory will shortly begin environmental testing.

Data from the instruments will be available to the public. It will be provided through the GLAST Science Support Center web site. Software for analyzing the data will also be available. Scientists with plans for research will be able to apply to the Guest Investigator program.

Education and Public Outreach are vital components of the GLAST project. A web site at Sonoma State University is the gateway to resources for students, educators, scientists, and the public.