Big satellite to drop from space soon

(CNN) -- A defunct 3.5-ton satellite could tumble from the sky in an uncontrolled descent and scatter debris over a swath of the planet within hours, NASA warned. <br><br>The aging spacecraft could re-enter

Wednesday, January 30th 2002, 12:00 am

By: News On 6

(CNN) -- A defunct 3.5-ton satellite could tumble from the sky in an uncontrolled descent and scatter debris over a swath of the planet within hours, NASA warned.

The aging spacecraft could re-enter the atmosphere as early as 10 p.m. EST Wednesday or as late as 7 a.m. EST Thursday, engineers with the space agency predicted.

Fragments from the Extreme Ultraviolet Explorer could scatter along a trail extending up to 625 miles (1,000 km), NASA said, but no one yet knows where.

Unlike the retired Compton Gamma Ray Observatory, which NASA safely guided from the sky into the ocean in 2000, the Extreme Ultraviolet Explorer (EUVE) has no onboard steering system.

Yet NASA scientists said there is little risk because most of the doomed satellite will burn up in the atmosphere.

"The probability of the few EUVE surviving pieces falling into a populated area and hurting someone is very small," said Ronald Mahmot of NASA's Goddard Space Flight Center in Greenbelt, Maryland, which originally managed the EUVE mission. "It is more likely that the small pieces will fall into the ocean or fall harmlessly to the ground."

Nevertheless, an estimated nine steel or titanium pieces could survive re-entry, ranging from four pounds to 100 pounds (1.8 kg to 45 kg).

As of Tuesday, EUVE was about 124 miles (200 km) above Earth, but loses about 15.5 miles (25 km) of altitude each day.

It is expected to begin disintegrating when it descends to within 50 miles (80 km) of the surface, then re-enter the atmosphere approximately seven hours later.

The re-entry window ranges from as far north as Orlando, Florida, and as far south as Brisbane, Australia. Scientists monitoring EUVE will not know the re-entry point until about 12 hours before impact.

Launched in 1992, the satellite lasted much longer than its intended three years. It studied the extreme ultraviolet spectrum for NASA and later the University of California, Berkeley, until it ceased operations a year ago.