"We're interested in listening to the stories gamma rays are telling us," said Steve Ritz, mission project scientist at NASA's Goddard Space Flight Center.
Gamma rays are ancient mariners, carrying tales at light speed from the farthest reaches and earliest days of our universe. They are the progeny of wild and violent events, of particles that have been accelerated to fantastic energies, and of dark matter annihilations.
Among the discoveries made by previous satellites was that the universe is dotted with powerful gamma ray bursts lasting only a few seconds and never reappearing. Searching out these bursts, which have been linked in some cases to the implosions of very massive stars into black holes, has become a current priority of space astronomy.
The GLAST team is searching for the deadliest detonations ever - gamma ray burst explosions. Nobody knows exactly what causes these short but indescribably energetic explosions, but a leading suspect is the collision of two neutron stars or black holes (and when you're talking about those kind of energies, it's the biggest bang you can have without creating a new universe). Another possibility is a super-supernova, which isn't the usual boring business of a star exploding, but the nuclear devastation of an incredibly large star that would make Zeus battling Odin look like two kids fighting in a sandpit.
These events are so mind-bogglingly intense that they can be detected from billions of light years away (and so billions of years in the past). Which is good, because you really don't want one to get any closer than that. One popular "sudden extinction" theory is that such a burst has happened within range of our own galaxy, but because the lethal gamma radiation moves at the speed of light, the first evidence we could 'detect' would be everybody and everything dropping dead. The only people who could investigate it are those who evolve from particularly hardy bacteria hidden deep in a rock somewhere, evolving for billions of years then looking at fossils full of iPhones and saying "Hmm, I wonder why everybody fell over all of a sudden".
GLAST will take high-resolution pictures of the invisible gamma-ray sky. Together, the Large Area Telescope (LAT) and the GLAST Burst Monitor (GBM) instruments will investigate the 10 keV to 300 GeV energy range, which includes some x-rays. The observatory will be launched into space to escape Earth's atmosphere, which blocks intense gamma radiation from reaching Earth's surface. The observatory will complete an orbit every 95 minutes, and can view the entire sky in two orbits.
The large area telescope is set to detect high energy gamma blasts accompanied by a "Burst Monitor" to detect lower energy gamma bursts - the phrase "lower energy burst" occupying the same levels of irony as "shallower ocean", "cooler blowtorches" and "less painful pokes in the eye with a pitchfork".
"If you put on gamma-ray glasses, you will see bright point sources, and you will also see a diffuse glow in our galaxy," says Rob Cameron, manager of a group at Stanford Linear Accelerator Center that will operate LAT and process its raw data.
A survey of the sky in the 1990s by the Compton Gamma Ray Observatory, no longer in operation, found 271 more-permanent sources of celestial gamma radiation, which turned out to be quasars and pulsars, but more than two-thirds of them have never been identified.
Gamma-ray radiation is the most energetic form of radiation, billions of times more energetic than the type of light visible to our eyes. What is happening to produce this much energy? What happens to the surrounding environment near these phenomena?
The Glast team hopes that the learning period will begin in about two months, after the satellite has been thoroughly checked out. In the meantime, and in keeping with American space-faring tradition concerning orbiting observatories, the craft will also be renamed.
According to the space agency, more than 12,000 names were submitted through a suggestion box on the Glast Web site, , before the box closed in March.