NASA telescope to scan extreme forces of space

Goddard scientists will examine gamma rays

June 09, 2008|By Dennis O'Brien | Dennis O'Brien,Sun reporter

If you think of the heavens as a peaceful place, with planets revolving around stars in timeless, predictable patterns, NASA plans to launch a $690 million space telescope next week could change your mind.

Managed by scientists at the Goddard Space Flight Center in Greenbelt, the Gamma-ray Large Area Space Telescope (GLAST) will spend five to 10 years probing things that blow up and crash into each other: gamma rays that explode, cosmic rays that bombard us and jets of energy that shoot out of black holes and speed through space in mystifying patterns.

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.

Nine feet high and 8 feet in diameter, GLAST will orbit 350 miles above the Earth, surveying the entire sky every three hours as it examines objects - invisible to the naked eye - that generate gamma ray emissions, the form of light with the highest energy.

"We're covering an energy range that almost hasn't been explored," said David J. Thompson, deputy project scientist and an astrophysicist at NASA Goddard. "We say we're working on the extremes of the universe. Gamma rays are the extreme."

Being in orbit will minimize the effects of the charged particles that surround Earth and would create unwanted static for GLAST's instruments: a monitor to detect gamma ray bursts and a large-area telescope to study them.

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

GLAST's flight operations and mission control center will be based at Goddard, where about 50 engineers and technicians will oversee the launch and initial operations. All but about a dozen staff members will eventually be assigned to other NASA projects once the instruments are fully operating, Grady said.

"We control the satellite here," he said.

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

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