Simulated GLAST all-sky survey image (above) vs. a current all-sky image from the Energetic Gamma Ray Experiment Telescope (EGRET) (below) on the Compton Gamma-Ray Observatory. This is an image of the entire gamma-ray sky. With 30-times greater sensitivity, GLAST will be able to distinguish many individual gamma ray sources from the blur of sources now observed by EGRET. Both images show the gamma-ray glow across the galactic plane caused by high-speed particle collisions within the interstellar medium. The EGRET all-sky survey comprises a collection of gamma-ray observations over a five-year period, all with an energy level greater than 100 MeV. (MeV is an energy unit equal to one million eV, or electron volts; the average photon of visible light carries about 2.25 eV.)
Credit: Seth Digel, NASA/USRA
A proposed model of the Gamma-ray Large Area Space Telescope (GLAST), a high-energy gamma-ray mission that is being studied and technology developed for flight in 2005 at a total cost of roughly $400M. GLAST will offer more than a 30x improvement in sensitivity over the Energetic Gamma Ray Experiment Telescope onboard the Compton Gamma Ray Observatory. The scientific mission of GLAST is to study nature's highest energy particle accelerators through observations of active galactic nuclei, pulsars, stellar-mass black holes, supernova remnants, gamma-ray bursts, the diffuse Galactic and extragalactic high-energy gamma-ray backgrounds, unidentified EGRET sources, and solar flares. GLAST will also search for annihilation line radiation from weakly interacting massive particles, or WIMPs, which may account for the dark matter.
Credit: NASA
