NASA Unfazed by Speeding Object Headed Past Earth : Space: Officials say they are more concerned about small debris that can harm satellites or shuttles.

Astronomers reported breathlessly this week that they had discovered a speeding object in space that will pass within 290,000 miles of Earth, but to the National Aeronautics and Space Administration, it was all much ado about nothing.

There are 100 million objects that pass through the Earth’s orbit around the sun every year, and about five a day pass within 290,000 miles of the Earth, said Don Kessler, chief scientist on NASA’s program to reduce the amount of debris in Earth orbit.

Asked if he was alarmed by the discovery of the latest object, Kessler said: “Not in the least.”

Kessler is far more concerned about the 7,000 objects of at least four inches in diameter that orbit within a few hundred miles of the Earth, because any of them could spell disaster for astronauts. The numbers are much higher for smaller pieces of debris. NASA has recently found that there are about 100,000 objects in near-Earth orbit that are at least half an inch in diameter.

It is these objects that pose the greatest threat, and Kessler said real progress is being made toward minimizing the danger.

The urgency of the problem of near-Earth debris was demonstrated dramatically in 1983 after the shuttle Challenger completed a mission. Ground crews found that a window on the spacecraft had been chipped during the flight. It could have been disastrous for the crew if the window in the pressurized craft had failed.

Engineers examined the damage and made a startling discovery. It was caused by a tiny fleck of paint, less than a hundredth of an inch in diameter, from some other man-made object.

Virtually every launch of any spacecraft leaves something in space, including satellites, spent rockets and debris from catastrophic failures. The U.S. Space Surveillance Network, which is part of the North American Air Defense Command, tracks all near-Earth objects that are greater than four inches in diameter.

Only about 5% of those 7,000 objects are functioning satellites. The rest of the items, which total more than 2,200 tons, consist of orbiting debris. Some of them have been there since the dawn of the Space Age.

Even objects too tiny to be tracked could damage a working satellite or endanger an orbiting crew, and NASA has been evaluating that hazard by using a sophisticated radar system that counts particles that pass through a radar beam.

Kessler, who is at the Johnson Space Center in Houston, said that study will be used to determine how much shielding will be required to protect the crew of the Space Station Freedom, which is scheduled to be completed toward the end of this decade. The station is to be permanently manned, so it will have to be shielded because it will almost certainly be hit from time to time by small pieces of debris.

Shielding adds considerable weight to the station, “so you don’t want to add more shielding than you have to,” Kessler said.

The current study suggests that 2,000 pounds of shielding will have to be provided for each habitable module aboard the station. The shielding consists of a thin sheet of aluminum about four inches from the wall of the pressurized capsule.

“That first sheet breaks the particle (of debris) up and spreads the energy” over the side of the module, he said.

If further studies indicate that is not enough protection, another protective sheet could be added to break up the debris even more, he said.

Future launches will generate less debris, Kessler believes, because of recent international agreements that require spacecraft to either burn or eject all their fuel by the time they reach orbit, thus reducing the chances of an explosion later.

Those latent detonations can spread debris over a wide area many years after the launch.

“One blew up on May 1 that had been up there for 16 years,” Kessler said. He said no one knows why the residual fuel exploded, but Kessler speculated that it could have been caused by collision with a small piece of debris.

With all that to worry about, NASA scientists were not particularly concerned over news reports that some object, possibly an asteroid or perhaps a piece of debris left over from the Apollo era, had been seen by a University of Arizona scientist Nov. 6.

The object measures less than 33 feet wide, and about 2 a.m. on Dec. 5 it will pass within 290,000 miles of Earth.

That is even farther away than the moon.