GREENBELT, Md. — The Compton Gamma Ray Observatory, after nine years of unprecedented studies of the universe, was deliberately slammed into the atmosphere Sunday, where it broke up and fell in a shower of hot metal over a remote stretch of the Pacific Ocean.
In the first planned and controlled crash of a satellite, NASA engineers directed the Compton through a series of suicide rocket firings that dropped it from a high orbit and sent it plunging to Earth.
"We got a positive confirmation," said mission reentry director Tom Quinn. "A job well done."
Compton was launched April 5, 1991. It died after completing 51,658 orbits of the Earth.
The 17-ton spacecraft worked perfectly through a final 30-minute rocket firing and then engineers watched on instruments in mission control as the speeding satellite heated, broke apart and then went silent. The craft started coming apart early Sunday; engineers estimated it took as long as 20 minutes for some of the lighter pieces to hit the ocean.
They said about six tons of superheated metal likely splashed into the Pacific.
Quinn said Air Force personnel aboard an observation plane gave "an extremely good confirmation" that the hail of hot metal showered the ocean where NASA engineers had planned.
"They were looking exactly where we told them to look and they saw it when we told them it would be there," said Quinn.
The target was a corridor starting about 2,500 miles southeast of Hawaii and extending for more than 2,000 miles toward the southeast.
Quinn said tracking signals from the spacecraft's final minutes indicated that its surviving pieces would safely hit the target area, far from any land.
Among the pieces predicted to hit the ocean were six 1,800-pound aluminum I-beams and parts made of titanium, including more than 5,000 bolts.
As the orbiter began breaking apart, Neil Gehrels, the project scientist, said: "This is a painful time for scientists who have used Compton for the last nine years."
A failed gyroscope prompted the space agency to decide in March to dump the $670-million Compton. Its 370-mile orbit would have kept it aloft for another 11 years, but NASA officials were worried that if more equipment failed, engineers would not be able to control the vehicle and it would make a dangerous random return to Earth.
The spacecraft flies over many populated areas, including Mexico City, Bangkok and Miami, and NASA engineers calculated that if Compton was allowed to fall on its own, there was one chance in 1,000 that someone would be killed.
A controlled reentry dropped the odds of a fatality to about one in 29 million.
Ed Weiler, NASA's chief scientist, decided it was too risky to keep the craft in orbit.
NASA endured a nerve-racking natural reentry once and was not anxious to risk it again. Skylab, a 78-ton abandoned U.S. space station, fell from orbit out of control in 1979. Debris dropped harmlessly into the Indian Ocean and across a remote section of western Australia.
Astronomers mourned the decision to destroy the Compton.
"The entire scientific community is disappointed," said Gehrels. "I was profoundly saddened.
"I am not second-guessing the decision," he added. "The people who had to make the decision had to consider safety. But from a scientific point of view it is a great loss."