NASA’s newest gamma-ray observatory soared on Wednesday into orbit, where it will search for the most energetic events the universe has to offer. The Gamma-ray Large Area Space Telescope (GLAST) tore through the cloudy skies of Florida atop a Delta II Heavy rocket from Cape Canaveral.

The $690-million mission succeeds the Compton Gamma Ray Observatory, which, in the 1990s, was the first instrument to study in detail the short-lived gamma-ray bursts thought to emanate from dying stars as they collapse into black holes or neutron stars. GLAST will also complement work being performed now by the Swift telescope, which looks for bursts in a lower-energy, mostly X-ray part of the electromagnetic spectrum.

GLAST “represents a huge increase in capability for gamma-ray astrophysics,” says project scientist Steve Ritz, of the Goddard Space Flight Center in Greenbelt, Maryland. “It’s a kind of leap you don’t get to make very often in a career.”

The satellite rode atop the fire of nine solid-fuel boosters and the liquid-fuel main engines. Deputy project scientist Julie McEnery, also of Goddard, watched from a beach and listened to launch commentary on a hand-held radio. “It’s a great day,” she said.

Flying high
Just 75 minutes after launch, the 4,300-kilogram satellite was 560 kilometres up, in low-Earth orbit. It detached from its second rocket stage and stretched out its solar arrays. In the next two weeks, Ritz says, the mission team will slowly test out its communication and mechanical abilities before turning on its two main science instruments.

One, a gamma-ray monitor, will look for low-energy gamma rays anywhere in the sky. When it detects one, a second instrument, a wide-view telescope, will automatically swing toward the event. This telescope sees 20% of the sky and scans the entire heavens once every three hours.
GLAST isn’t limited just to the study of gamma-ray bursts; it has a whole list of scientific subjects ranging from dark matter to blazars, the variable energy sources associated with supermassive black holes at the centres of galaxies. Ritz says that, outside of gamma-ray bursts, the most fruitful terrain for GLAST may be the study of so-called active galactic nuclei, where black holes seem to accelerate jets of particles and shine beams of light toward Earth.

GLAST’s sensitivity ranges across seven orders of magnitude, from 20 mega-electronvolts to 300 giga-electronvolts. That will be a boon for astronomers not only working in space but also on the ground, where they can build larger collecting areas to catch the light but must deal with lower fluxes and more atmospheric noise. GLAST will fill an important and hitherto-unexplored gap in the electromagnetic spectrum, says Frank Krennrich, an astrophysicist at Iowa State University in Ames.

“I think GLAST is going to really open up the gamma-ray sky,” says Krennrich, who is Iowa State’s principal investigator on an Arizona telescope that looks for the light showers caused when gamma rays collide with the atmosphere. “They can tell us where to point our telescopes.”