The spacecraft, built by General Dynamics in Phoenix, is expected to launch from Cape Canaveral on Wednesday or soon after, depending on when tests are completed on the Delta II rocket that will send it into orbit.
NASA expects to release the first images - a picture of the sky in the gamma ray portion of the spectrum - by the end of the month, Thompson said. But don't expect the kind of breathtaking images created by the Hubble Space Telescope. Images from gamma ray radiation just aren't as striking as stars and galaxies captured in the visual portion of the spectrum, Thompson said.
"The physics just isn't right for it," he said.
The mission is intended to study a wide range of phenomena, including cosmic rays, gamma rays and active galactic nuclei (AGNs) - galaxies with luminous cores that produce powerful jets.
GLAST is designed to see thousands of AGNs and resolve questions about how the jets form, and how they speed through space in relatively long, thin columns. In laboratory experiments, scientists have tried to re-create such superheated, high-energy columns with thermonuclear reactions, but have yet to succeed, experts say.
"Plasma instabilities occur that break up any streaming, and yet here we have objects in space that travel hundreds, if not thousands, of light years in these very collimated streams," said Richard E. Lingenfelter, an astrophysicist at the University of California, San Diego. "The fact that they seem to be so narrowly collimated over such long distances is fascinating."
Gamma rays are believed to originate from exploding stars, called supernovas, which create black holes and release huge amounts of energy. GLAST may confirm these origins and find new ones, experts say.
"A lot is known about gamma rays, but there's always the likelihood that we've missed something," Lingenfelter said. "To me, the most interesting thing is being able to identify all the individual sources, both galactic and extragalactic."
Cosmic rays are a major source of energy in the universe, but much about them remains a mystery, including what accelerates them to nearly the speed of light.
GLAST will test the leading theory - that acceleration is generated by shock waves formed in the remnants of supernovas - by measuring the spectra of gamma rays emanating from supernova remnants.
GLAST is an international mission. Researchers from Germany, France, Italy, Japan and Sweden helped design and construct parts of the spacecraft. The United States is paying $600 million of the mission costs, and foreign contributions totaled $90 million, NASA said.
NASA has agreed to fund the mission for five years and could extend it another five years if discoveries generate sufficient interest, Thompson said. He's optimistic about the potential.
"Any of the things we see with this gamma ray telescope are going to be big," he said. "They have to be: Gamma rays are the biggest forces in nature."
dennis.obrien@baltsun.com
