NASA has announced the selection of an investigation to be flown on the Gamma Ray Large Area Space Telescope (GLAST) mission, planned for launch in 2005. In addition to the flight investigation, NASA selected four interdisciplinary scientist investigations to broaden the scientific expertise available to the project.
GLAST will explore the most energetic and violent events in a quest for the ultimate sources of energy in the Universe. Objects explored will include distant galaxies fueled by super massive black holes at the center, neutron stars and individual black holes, remnants of stars that have ended their life with an explosion (supernova), and many others at the extremes of mass and energy.
Almost 300 objects have been observed to emit high-energy gamma rays and yet less than half of these have been identified with objects seen at other wavelengths. What mysteries are lurking in these illusive objects? The GLAST mission will also explore the very high-energy component of gamma-ray bursts, still one of the greatest mysteries of astrophysics.
Even the dimmest of these bursts is as bright as the brightest of the steady high-energy gamma-ray sources. The discovery of high-energy gamma rays from these mostly low-energy gamma-ray events constrains the models for the gamma-ray "flash bulbs." The major improvement in sensitivity and precision of the observations will provide an opportunity for new discoveries. One possibility is the search for evidence for some of the most exotic particles predicted by physicists to be candidates for the dark matter of the Universe.
The GLAST mission's primary scientific objectives require an instrument with large collecting area, imaging capability over a very large field of view, the ability to measure the energy of the gamma rays over an unprecedented range of energies, and time precision to study transient phenomena characteristic of gamma-ray sources. The instrument must be carefully designed in order to weed out the rare gamma rays from the much more abundant cosmic rays, and other backgrounds such as gamma rays produced by these cosmic rays slamming into the molecules in the Earth's atmosphere.
The investigation selected by NASA is the "GLAST Large Area Telescope Flight Investigation: A Particle-Astrophysics Partnership to Explore the High-Energy Universe." The Principal Investigator is Professor Peter F. Michelson of Stanford University. The investigation is a collaborative international effort involving a major contribution from the U.S. Department of Energy, and contributions from France, Italy, Japan and Sweden. The instrument covers the energy range from 10 million to 1 trillion electron volts. It has about 50 times the sensitivity of any previous gamma-ray investigation and covers a much broader energy range with high angular precision.
NASA's cost to develop the GLAST mission is approximately $200 million, which includes approximately $70 million for the primary instrument.
The four interdisciplinary scientists selected and their investigations are:
* Stephen Thorsett of the University of California at Santa Cruz, "Observations of Rotation Powered Pulsars in Support of GLAST." This work will provide important information to allow the study of gamma rays from pulsars by the primary instrument.
* Professor Brenda Dingus of the University of Wisconsin, Madison, "GLAST: A GeV All-Sky Monitor of Transient Phenomena." The purpose of this investigation is to alert other space- and ground-based observers of the occurrence of a transient phenomenon, such as a gamma-ray burst or gamma-ray flaring quasar, so that the object may be observed at many wavelengths simultaneously to obtain the most information possible.
* Dr. Charles D. Dermer of the U.S. Naval Research Laboratory, Washington, D.C., "Exploring the Nonthermal Universe: Analysis and Modeling to Maximize the Scientific Impact of GLAST." This investigation will provide a theoretical framework for the GLAST studies.
* Dr. Martin Pohl , Ruhr University, Bochum, Germany, "Modeling the diffuse galactic gamma-ray emission." The model provided in this work is essential to the analysis of GLAST data.
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