Officials at the National Aeronautics and Space Administration (NASA) said the 17-tonne observatory began its descent shortly after midnight Sunday (0400 GMT) and reentered the Earth's atmosphere "as expected" at 0705 GMT, with debris that survived reentry falling into the ocean about 4,000 kilometers (2,500 miles) southeast of Hawaii.

"Everything indicates that we hit the target," said a NASA spokesman at the Goddard center, based in Laurel, Maryland, adding that more detailed information about the debris that rained down on Earth would be available over the next 24 hours.

NASA officials said the observatory was too large to be destroyed entirely by reentering Earth's atmosphere, and that orchestrating an ocean splashdown was the most prudent course of action.

"This location provides a landing area with a very large margin of safety," the Goddard Space Flight Center, monitored the satellite, said in a statement.

The space agency fired up the satellite's engines on Tuesday and Wednesday to begin the observatory's descent and did so twice again early Sunday which caused the craft to plunge to Earth.

During its 760-million dollar nine-year mission, the observatory allowed scientists to study celestial sources of gamma-rays, which are usually generated by the most violent cataclysms in the universe, emitting huge amounts of energy.

Thanks to the satellite, astronomers were able to identify more than 400 sources of gamma-rays, a tenfold increase from the period before it was placed in orbit.

"New discoveries made by Campton changed our view of the universe in fundamental ways," said NASA program director Alan Bunner.

Initially, NASA had planned to retire the observatory in 1996, but its mission was extended by four more years.

However, one of the three gyroscopes which allow the satellite to maintain its altitude of 511 kilometers (317 miles), broke down several months ago, and the observatory lacked fuel to move into a higher orbit.

According to scientists, a loss of one of the two remaining devices would have rendered the satellite uncontrollable and risked creating a hazard to densely populated areas upon its fall. SPACE SCIENCE
Gamma Ray Scope To Be De-orbited
Greenbelt - March 24, 2000 - NASA's extremely productive and long-lived Compton Gamma-Ray Observatory mission -- which exceeded its mission by four years and completely changed ideas on the most important unsolved puzzles in astrophysics -- has come to end with the failure of one of the satellite's three gyroscopes.