NASA’s new gamma ray telescope all set to be launched

Within a few hours from now, the latest weapon in NASA's arsenal to probe into the secrets of interstellar space, the Gamma Ray Large Area Telescope (GLAST) is scheduled to blast off from Cape Canaveral Air Force Station in Florida aboard an unmanned Delta rocket.

The space laboratory, built by General Dynamics, is 2.8m (9.2ft) high and 2.4m (8.2ft) in diameter, and will orbit at an altitude of 565km (350 miles) above the earth's surface. 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.

Managed by scientists at the Goddard Space Flight Center in Greenbelt, GLAST will spend five to ten years probing explosive phenomena like cosmic rays that bombard the earth, jets of energy that shoot out of black holes and speed through space in mystifying patterns and dense neutron stars with powerful magnetic fields whose one teaspoonful can weigh several million tons.

Astronomers hope to shed light on some of the most powerful forces in the universe - and shatter stereotypes in the process, NASA officials say.

"We look out into space and see stars shining and think of the universe as a static place, but it isn't. In this gamma ray region, things are going off and exploding and just speeding away, all in seconds," said Kevin Grady, GLAST's Goddard-based project manager.

This telescope will study, apart from other things, some of the most destructive phenomena in the known universe – gamma ray bursts (GRB). GRBs typically release more energy in one second that our sun will emit in its entire 10 billion years of existence.

"We've only scratched the surface of the how and why of these gamma-ray phenomena," said Dave Thompson, a deputy project scientist from NASA. "We have a lot to learn about how they work, and, more importantly, how these objects and phenomena affect the Universe. This is where GLAST comes in."

Explaining the importance of gamma rays, Thompson added, ''We're covering an energy range that almost hasn't been explored. We say we're working on the extremes of the universe. Gamma rays are the extreme.''

Gamma radiation is light's most energetic form, millions to hundreds of billions of times more powerful than visible light. The energies are so high that Albert Einstein's famous E=mc2 equation, which captures the relationship between matter and energy, provides the framework for designing how the telescope works.

Gamma rays, which are pure energy, slam into a layer of tungsten in the detector and split into pairs of subatomic particles, an electron and its antimatter partner, a positron. Layers of silicon can then trace the direction of the incoming gamma rays. Another detector, called a calorimeter, absorbs and measures the particles' energy.

Many more particles besides gamma rays will bombard GLAST's detectors, so the telescope wears what engineers call a "hat" to sort out cosmic ray hits and other unwanted visitors.

The main instrument aboard the spacecraft is the Large Area Telescope, or LAT. Gamma-rays carry far to much energy to capture in the conventional way, so this is a telescope without lenses or mirrors. Instead, the LAT uses silicon detectors and layers of metal foil to track the energetic radiation from outer space.

Once GLAT reaches orbit, about 14 days will be spent checking out the spacecraft. In the third week after launch, the spacecraft's instruments will be turned on for tuning and calibration.

Every three hours, a solid-state recorder will transmit data to Goddard by way of a satellite and a terminal in White Sands, New Mexico. Data from the monitor will be processed at NASA's Marshall Space Flight Center in Huntsville, while telescope readings will be processed at the Stanford Linear Accelerator Center in Menlo Park, California.

GLAST will also try to find answers to one of the most daunting problems of modern physics – the prevalence and constitution of ''dark matter''. Scientists are of the opinion that matter of known origins comprises only 20 per cent of the universe, with the rest of the mass contributed by matter about which not much is known, and hence named ''dark matter''.

According to scientists, putting telescopes in orbit, beyond the filter of Earth's atmosphere, has opened new windows for exploring the universe.

"Throughout all of human existence, there's been a shared experience of looking up at the night sky at the stars … but it's only very recently that we have come to understand that all that light is only secondary byproducts of high-energy physical properties," said Steve Ritz, the lead scientist for GLAST.

"What we see when we look in other parts of the electromagnetic spectrum is very different than what we see with our natural eyesight," Ritz added. "GLAST is giving us a chance to peak behind the curtain or under the hood to see how things are working."