Huge NASA telescope headed for fiery descent in June

The observatory was launched in 1991

March 23, 2000
Web posted at: 8:10 p.m. EST (0110 GMT)

From Space Correspondent Miles O'Brien

GREENBELT, Maryland (CNN) -- After nearly nine years in space, a 35,000-pound NASA observatory in low-Earth orbit is destined for a fiery descent this June into the Pacific Ocean southeast of Hawaii.

Sources tell CNN that during a meeting Thursday morning at NASA headquarters in Washington, senior managers at the space agency made the decision to send the $600 million Compton Gamma-Ray Observatory to a watery grave in the Pacific on June 3.

NASA confirmed the decision at a Friday news conference.

"It has been a terrific mission; We have certainly gotten everything -- and more -- that we expected out of GRO," said Preston Burch, deputy program manager for space science operations at NASA's Goddard Space Flight Center. "Now is the time to bring it back safely."

In early December, the observatory lost one of its gyroscope systems, leaving it with the minimum of two required to conduct scientific observations.

Engineers believe they cannot safely de-orbit the satellite unless both gyros remain operative, leaving the observatory with only one failure away from becoming a possible space-debris hazard. Scientists say they are also concerned about the operability of other critical systems on the satellite.

"It is an old satellite and some systems are failing," Burch said. "A major failure in a critical subsystem could hinder our ability to bring it down in a controlled way."

According to estimates, the debris field will be 26 kilometers (16 miles) wide by 1,552 kilometers (962 miles) long, putting 40,000 square kilometers of ocean in harm's way.

Engineers generated the estimate based on computer modeling of other controlled re-entries -- such as the space shuttle's external fuel tank -- which routinely fall harmlessly into the Indian Ocean following launches.

"We're very concerned about hitting any land areas that are populated," Burch said. "We are being extremely conservative in our planning. There is plenty of margin of safety."

Launched from the space shuttle Atlantis on April 5, 1991, the Compton Gamma-Ray Observatory was designed to orbit for at least two years and gather information on electromagnetic radiation, providing insight into the origins of the universe. While the scientific observations have continued -- a recent set of results was released this week -- the staff and the funding are currently very lean.

Compton is the heaviest unclassified satellite ever deployed by a space shuttle. The Hubble Space Telescope, launched in April of 1990, weighs about 4,500 kilograms (10,000 pounds) less than Compton, but is larger.

Unlike Hubble, Compton was not designed to be serviced by astronauts in its 270-mile orbit.

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NASA Homepage
  • Compton Gamma Ray Observatory
  • NASA Goddard Space Flight Center Homepage
  • An Overview of the Compton Gamma Ray Observatory

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