A fiery goodbye to Compton Gamma Ray Observatory
BY JUSTIN RAY
Posted: June 4, 2000
The 17-ton telescope plummeted into the atmosphere just after 2 a.m. EDT (0600 GMT) after a week-long process of lowering its orbit through a course of lengthy thruster firings. Contact was lost at 2:10 a.m. EDT (0610 GMT) as controllers saw temperatures skyrocketing and indications the craft was tumbling.
"At this point, the spacecraft is probably breaking up," said Thomas Quinn, the reentry coordinator.
"We did expect to lose the solar arrays fairly early, they're going to pop off, some of the loose elements of the spacecraft are going to start to fall apart. As things heat up, the primary structure's going to start to melt and larger components are going to start to break off the spacecraft."
"This is a painful time for the scientists who have used the Compton Observatory for the last nine years as the spacecraft plunges into the atmosphere and flies apart," said project scientist Neil Gehrels.
Read our Mission Status Center for reports filed throughout the final hours of CGRO's life and the reentry.
Experts said six 1,800 pound aluminum I-beams, titanium parts and more than 5,000 bolts from CGRO would survive the reentry.
Observers aboard an Air Force surveillance aircraft in the area confirmed seeing the satellite breaking up and landing in the planned safety zone.
Officials said it would take a couple of days to determine the exact location and dimensions of the debris field.
CGRO's demise ends one of NASA's most successful science missions, which began when the observatory was launched into space aboard shuttle Atlantis on April 5, 1991.
Compton made 51,658 orbits around Earth.
Built by TRW, the $671 million craft was the second of NASA's Great Observatory family, along with sisters Hubble Space Telescope, Chandra X-ray Observatory and the future Space Infared Telescope Facility.
NASA ordered the controlled reentry in March after one of CGRO's three stabilizing gyroscopes failed. The space agency decided to deorbit the craft to protect public safety because an additional failure could have meant a dangerous crash like Skylab in 1979.
Officials calculated there was a 1-in-1,000 chance a person could be killed by CGRO if it reentered uncontrollably. The craft's orbital track ranged from 28.5 degrees to either side of the Equator.
"Our goal for the science community was a five-year mission to open the gamma ray universe to observation for the first time," Ed Weiler, NASA's associate administrator for space science, told reporters Sunday morning. "We certainly have met our commitment to the science community. Compton has greatly exceeded its expectations with a 9-year mission."
During its tenure in space, CGRO studied violent and invisible gamma ray bursts, antimatter fountains and particle jets streaming millions of miles per hour away from black holes. The telescope detected more than 400 gamma ray sources, 10 times more than were previously known, and recorded over 2500 gamma ray bursts when only 300 had been detected before.
MISSION STATUS CENTER