The Mission

The

GLAST Mission is part of NASA's Office of Space and Science Strategic Plan, with launch anticipated in 2006. GLAST is a next generation high-energy gamma-ray observatory designed for making observations of celestial gamma-ray sources in the energy band extending from 10 MeV to more than 100 GeV. It follows in the footsteps of the CGRO-EGRET experiment, which was operational between 1991 and 1999.

The key scientific objectives of the GLAST mission are:

1. To understand the mechanisms of particle acceleration in AGNs, pulsars, and SNRs. This understanding is a key to solving the mysteries of the formation of jets, the extraction of rotational energy from spinning neutron stars, and the dynamics of shocks in SNRs.
2. Resolve the gamma-ray sky: unidentified sources and diffuse emission.Interstellar emission from the Milky Way and a large number of unidentified sources are prominent features of the gamma-ray sky.
3. Determine the high-energy behavior of gamma-ray bursts and transients. Variability has long been a powerful method to decipher the workings of objects in the Universe on all scales. Variability is a central feature of the gamma-ray sky.
4. Probe dark matter and early Universe. Observations of gamma-ray AGN serve to probe supermassive black holes through jet formation and evolution studies, and provide constraints on the star-formation rate at early epochs through photon-photon absorption over extragalactic distances. There are also the possibilities of observing monoenergetic gamma-ray "lines" above 30 GeV from supersymmetric dark matter interaction; detecting decays of relics from the very early Universe, such as cosmic strings or evaporating primordial black holes; or even using gamma-ray bursts to detect quantum gravity effects.

The GLAST LAT has a field of view about twice as wide (more than 2.5 steradians), and sensitivity about 50 times that of EGRET at 100 MeV and even more at higher energies. Its two year limit for source detection in an all-sky survey is 1.6 x 10^-9 photons cm^-2 s^-1 (at energies> 100 MeV). It will be able to locate sources to positional accuracies of 30 arc seconds to 5 arc minutes. Yet, it is a relatively small and inexpensive mission, which will be able to be launched on a Delta II rocket.