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 to 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 re-entry director Tom Quinn. "A job well done."
Compton was launched April 5, 1991. It died after completing 51,658 orbits of the Earth.
Scientists want to know why NASA has issued a death sentence to a functioning and, they say, extremely useful satellite.
CBS News Correspondent Eric Engberg reports the reason NASA sent the $760 million Observatory (GRO) into an irreversible suicide dive may have to do with Russia's failing MIR orbiter.
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 about 2:14 a.m. and pieces began falling into the water five minutes later. Engineers estimated it took as long as 20 minutes for some of the lighter pieces finally to hit the ocean.
They said some six tons of superheated metal likely survived the scorching re-entry and splashed into the Pacific.
Quinn said Air Force personnel aboard an observation plane gave an "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 some 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, far from any land.
Among the pieces predicted to survive re-entry and 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 plunged toward silence and 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 overflies many populated areas, including Mexico City, Bangkok and Miami, and NASA engineers calculated that if Compton was allowed to fall on its own, there wa one chance in 1,000 that someone would be killed.
A controlled re-entry dropped the odds of a fatality to about one in 29 million.
Hundreds of scientists who had been using the Compton's world-class research over the years had petitioned NASA and Congress to keep the telescope in the air, and explore the option of fixing the gyroscope problems that are necessitating its demise.
"Sending it the last command and watching the plug pulled on it is sort of like you're watching your dog get shot," says James Ryan, a Physics professor at the University of New Hampshire, and one of the scientists working on the Compton project. He says he's mystified by what he calls NASA's rush to deep-six the telescope rather than fix it.
"Things fail on spacecraft. They have for years. They'll always fail on spacecraft," says Ryan. "If something fails, what you do is call up some backup piece of hardware or backup operating mode and you institute it and if its safe you just keep operating it. Scientists around the country have been scratching their heads trying to figure out what is behind this action on NASA's part given that we have what we believe is a conceivable way of extending the mission."
But Edward Weiler, NASA's chief scientist, claimed the safety concerns must be paramount. "I dont want to explain to a little lady in Calcutta, India, 'Hey, I know you child was killed by a piece of GRO, but we published seven more papers,'" he said.
But another reason NASA turned to the "ultimate solution" may lie with the Russian space station MIR. CBS News Correspondent Sharyl Attkisson has learned NASA recently briefed the White House about the very real possibility that MIR could soon plunge wildly to earth.
The briefing document was titled: "MIR Reentry USG Observation Implementation Plan" and was dated March 15, 2000. It said:
- The U.S. government cannot predict where surviving MIR hardware will impact the ground.
- Components of MIR will survive reentry.
- Damage could be significant if the entry is uncontrolled and it impacts a populated area.
To prevent a horrific scenario, NASA is urging Russia to send MIR into a controlled kamikaze dive in the coming months. Russia hasn't agreed. Which gets back to one of the reasons why NASA may have been so quick to accept the demise of the Compton Telescope.
"NASA can't very well lecture the Russians about deorbiting the MIR space station if they are reluctant to deorbit their own satellite, which is known to be unhealthy at this moment," says CBS News Space Consultant Bill Harwood.
The world faced the threat of a haphazard landing back in 1979 when Skylab crashed to earth. It broke up at a much lower altitude than NASA had predicted, raining debris over Australia. Nobody was hurt.
Still astronomers mourned the deision 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."
When Compton took its last bit of data - an observation of the sun on May 26 - it was still functioning smoothly, except for the failure of one of its three gyroscopes. The craft exceeded its expected mission lifetime by more than four years.
Compton was the first major space observatory to make a systematic survey of natural sources of gamma rays - an invisible ray that is the most energetic part of the electromagnetic spectrum.
In nine years of observations, said Gehrels, Compton has changed the way astronomers view the universe.
The craft detected more than 2,600 gamma ray bursts and showed that they are occurring throughout the universe.
"We discovered they came from everywhere, and from huge distances," said Gehrels. "We know now they are the biggest explosions in the universe because they are so far away and we see them so brightly."
What causes gamma ray bursts is still a puzzle.
Compton discovered hundreds of previously unknown sources of gamma rays, including 30 new and exotic objects that are still not completely understood. It detected gamma rays streaming from black holes, from exploding stars and from the sun. The data has helped astronomers, for the first time, begin to understand how black holes can trigger jets of X-rays and gamma rays that streak outward at near the speed of light.
Astronomers have written about 2,000 papers based on data from Compton and more than 100 astronomers annually used the spacecraft to make observations, said Gehrels.
Compton was the second of NASA's great, orbiting observatories, spacecraft that get a clear view of the universe above the obscuring effect of the atmosphere.
The other two, the Hubble Space Telescope and the Chandra X-ray Observatory, are still in orbit, working smoothly.