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Saturday, September 24, 2011

NASA Says Satellite Fell in Pacific - WSJ.com

SEPTEMBER 24, 2011, 4:40 P.M. ET

NASA Says Satellite Debris Fell in Pacific

Reuters

The Upper Atmosphere Research Satellite is deployed by the Space Shuttle Discovery in this NASA handout photo dated September 1991. The six-ton NASA science satellite plunged to earth early Saturday.

By ANDY PASZTOR

NASA said all debris from a decommissioned research satellite appears to have dropped in a remote section of the Pacific Ocean well "away from the western coast of the U.S," but the precise spot may never be pinpointed.

Nick Johnson, chief scientist for orbital debris at the National Aeronautics and Space Administration, told reporters the fiery trajectory of the 13,000-pound satellite ended as it crossed eastward over portions of the Indian Ocean and Africa for the final time. It then most likely disintegrated and scattered debris over a roughly 500-mile stretch across the northern portion of the Pacific.

About 11 hours after the splashdown, Mr. Johnson said there weren't any credible reports about debris falling on land or anyone recovering satellite parts—contrary to widespread Internet speculation about purported remnants of the satellite falling to the ground in Canada or elsewhere. But "we may never know" precisely where the debris ended up, he told reporters, as ground-based sensors and other tracking devices provide only approximate locations of where the satellite started breaking up, and debris began falling vertically. NASA also said it hadn't received any reports of debris sightings from aircraft or vessels.

The descent of the 20-year-old satellite, which stopped collecting climate data about six years ago, was the largest object NASA has tracked in an uncontrolled re-entry for more than three decades. But about once a year, similar-size space objects plummet back to Earth amid commands from the ground.

No reports of space junk or debris causing injuries on the ground have been substantiated since the Space Age began more than five decades ago.

The satellite's descent path crossed over portions of Africa and inhabited sections of northern Canada. But in its latest update Saturday, NASA said that the best simulations of Pentagon trackers, as well as those developed separately by a government-wide team of experts, strongly indicate "all that debris dropped in the Pacific Ocean."

In the past, NASA and the Pentagon have failed to precisely map the re-entry of some defunct satellites, or verify where debris fell.

As "practically the entire re-entry path" during the final phase was over water, Mr, Johnson said, all the evidence so far points to pieces ending up in the Pacific. But he added "we don't exactly know where the debris field is."

The U.S. largely relies on ground-based sensors and sophisticated computer systems to keep track of more than 20,000 pieces of orbiting debris, and the same system is used to follow satellites or other objects that fall back to Earth.

More recent satellites are designed so that operators can bring them out of orbit and control their trajectory as they take the final plunge through the atmosphere.

The risks posed by collisions between two pieces of orbiting debris, a topic that increasingly preoccupies some military and aerospace experts, are significantly greater. The debris is essentially the residue of hundreds of rocket launches, decommissioned satellites, exploration missions and other man-made objects left circling Earth.

With an estimated 750 or more satellites now in orbit—and many more nations now seeking to launch satellites than ever before—overall collision hazards are expected to increase. Experts worry the threats are particularly significant around some widely used orbital locations. Astronauts aboard the international space station periodically are forced to take emergency steps to deal with threats.

Two years ago, a drifting and powerless Russian satellite smashed into and destroyed a commercial satellite operated by Iridium Communications Inc., a provider of phone and data services based in McLean, Va. The collision happened because Pentagon radar sites on the ground and U.S. government assets in space weren't closely tracking the merging courses of the two satellites. At the time, top Air Force officials said the U.S. could closely track and issue collision warnings for only a couple of hundred pieces of orbiting debris.

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http://online.wsj.com/article/SB10001424053111903703604576590114049454164.html

Heads Up! The Sky is Falling!!!:O...

Don