Satellite could have dropped over Egypt

Artist's depiction of the Extreme Ultraviolet Explorer

By Richard Stenger
CNN Sci-Tech

(CNN) -- Most of a falling satellite likely burned up in the atmosphere over Egypt but surviving chunks could have crashed or splashed into the planet, U.S. space officials said Thursday.

Whether or where fragments of the 3.5-ton Extreme Ultraviolet Explorer (EUVE) landed could remain unknown for some time, NASA spokesperson Dolores Beasley said.

NASA revised predictions several times as the defunct satellite took its final 90-minute laps around the world. But based on radar tracking by the U.S. Air Force, the agency concluded Thursday that it re-entered the atmosphere at about 11:15 p.m. EST the night before.

"We expected EUVE could come in at a number of points along the ground track," said NASA engineer Scott Hull. "The actual location of EUVE's re-entry was within the predicted orbit track."

Out of control

Predicting the planetary bulls-eye had proven difficult because the aging NASA satellite had no onboard steering system. Circling the planet in a rapidly decaying orbit, EUVE tumbled from space in an uncontrolled manner.

VIDEO EUVE's final laps in space  (MPEG / 1M) Courtesy: Analytical Graphics, Inc    Mission at a glance Satellite: Extreme Ultraviolet Energy Explorer Weight: 7,000 pounds (3,200 kilograms) Lifetime: Launched in 1992 from Cape Canaveral, EUVE conducted observations until 2000 Instruments: Three scanning telescopes and a deep sky survey spectrometer Highlights: Offered new insights into comets, white dwarfs and the atmospheres of stars

Up to nine stainless steel or titanium pieces could have survived re-entry, ranging from 4 pounds to 100 pounds (1.8 kg to 45 kg), NASA said. The debris trail could have extended up to 625 miles (1,000 km).

Despite the uncertainty, space agency scientists said there was little risk to humans.

"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.

Bovine bomber

Launched in 1992, EUVE was the first space observatory dedicated to studying extreme ultraviolet light.

The $215 million satellite lasted much longer than its intended three years, studying celestial objects first for NASA and later the University of California, Berkeley, until it ceased operations one year ago.

In contrast to EUVE's uncontrolled descent, NASA in 2000 safely guided the Compton Gamma Ray Observatory into the ocean because the 17-ton craft had an onboard steering system.

Likewise, in 2001, Russian ground controllers relied on similar means to coax the 135-ton Mir space station, the heaviest object in Earth orbit besides the moon, into its watery grave without a hitch.

The most massive NASA spacecraft to re-enter the atmosphere in an uncontrolled descent was the 78-ton Skylab space station, which in 1979 scattered debris in the Indian Ocean and an isolated stretch of Western Australia.

Orbital debris has never been known to injure a human, but legend has it a chunk of Skylab brought an untimely end to an Australian cow.