Satellite ‘to fall to Earth this week’

A 7,000lb science satellite will fall from the sky this week, and Nasa says a few pieces of metal could hit the Earth, although probably not in a populated area.

The US space agency announced today that the Extreme Ultraviolet Explorer is falling at the rate of 15 miles a day from an orbit of about 124 miles and should make a final plunge to Earth between 0300 Irish time and 1200 Irish time on Thursday.

Officials said the satellite would start breaking apart when it hit the upper edge of the atmosphere, about 50 miles high. It is expected to complete four or five more 90-minute orbits before its final descent.

Most of the spacecraft is expected to come apart and burn up in the atmosphere during its high-speed fall. Nasa engineers, however, said it was possible that up to nine stainless steel and titanium pieces, weighing up to 100lb, will reach the Earth’s surface.

The satellite pieces, if they survive the fall, are expected to land in a debris field stretching some 625 miles under the orbital path. The re-entry point is expected to be determined about 12 hours before the final fall, Nasa said, but would probably not be in populated areas.

In 2000, NASA engineers successfully directed a safe de-orbit of the 17-ton Compton Gamma Ray Observatory, using rockets aboard the satellite to bring it down in a remote part of the Pacific Ocean.

The Extreme Ultraviolet Explorer, however, does not have the on-board rockets needed to direct the re-entry. As a result, it will fall uncontrolled within a belt around the middle of the Earth stretching as far north as Orlando, Florida and as far south as Brisbane, Australia. This belt includes such highly populated areas as Mexico City, Bangkok and Miami.

The largest uncontrolled re-entry by a Nasa spacecraft was Skylab, a 78-ton abandoned space station that fell from orbit in 1979. Its debris dropped harmlessly into the Indian Ocean and across a remote section of western Australia.

Launched in 1992, the Extreme Ultraviolet Explorer collected images of more than 1,000 celestial objects detected in the extreme ultraviolet part of the spectrum. The craft was designed to work for three years, but it was operational for eight. The observation programme ended last year.