"We couldn't be happier," said NASA project scientist Steven Ritz.
The $690 million telescope, supported by six countries, will pick up where NASA's Compton Gamma Ray Observatory left off before its deliberate destruction in 2000, but in a bigger and better way.
With superior new technology and insight gained from Compton and other telescopes, Glast will be able to do in three hours, or two orbits of Earth - survey the entire sky - what Compton took 15 months to do. What's more, Glast and its particle detectors are much more sensitive and precise, and should provide an unprecedented view into the high-energy universe.
"In a sense what Glast is doing is giving us a chance to peek behind the curtain or look under the hood for how things are working, and it's only by doing this sort of exploration that we're able to learn these things. It's a form of scientific enlightenment," Ritz said earlier in the week.
Gamma rays - at the extreme end of high energy - go "splat" when they encounter Earth's upper atmosphere, so scientists must look to space observatories to uncover the secrets of gamma radiation.
Physicists want to know more about the huge jets of particles and radiation shooting out of black holes at nearly light speed, and the gamma ray bursts, or explosions, that take place in the universe every day. They also want to see what else might be out there shining in gamma radiation, possibly shedding light on the mysterious dark matter making up so much of the universe.
Glast will convert incoming gamma rays into pairs of electrons and positrons - in other words, matter and antimatter - and figure out where they came from in the cosmos. Researchers then will be able to pinpoint the source.
Ritz expects 100,000 charged particles to stream through the telescope for every gamma ray, with about two gamma rays a second.
"We really have to find that needle in a haystack," he said.
With the National Academy of Sciences pushing gamma ray observations as a high priority for NASA, work on the nearly 5-ton telescope began in 2000, after eight years of planning. It originally was scheduled for a late 2006 launch, but extra time was needed to work on the spacecraft. More recently, rocket issues led to delays.
In addition to the United States, participating countries include Italy, France, Germany, Sweden and Japan.
NASA plans to drop Glast's awkward acronym name in another month or two; the winning name will come from 12,000 entries submitted via the Internet.
Science operations are expected to begin in earnest in August. The control center is at Goddard Space Flight Center in Greenbelt, Md.
"We can't wait," Ritz said.
