Dust, debris from comet threaten 600 satellites Little can be done to prevent damage from annual meteor shower

November 04, 1998|By NEWSDAY

Tiny chunks of material that constantly boil off Comet Tempel-Tuttle may pose a hazard for hundreds of space satellites when Earth passes through the debris' path in mid-month, scientists report.

As Earth draws nearer to this rain of Leonid meteors, efforts are mounting to protect valuable satellites that relay radio messages, scan the ground and watch the stars.

There is concern that delicate space instruments may be harmed, although the amount of danger, if any, is not known.

The Leonid meteors -- leftovers from the comet's gradual disintegration -- come streaking down through Earth's atmosphere once a year, appearing to radiate from the constellation Leo.

Viewed from the ground, the Leonids sometimes put on a spectacular display, a so-called meteor storm, as Earth slips through the comet's fine leftovers.

Astronomers suspect this month's encounter may be the most intense in 33 years.

So space scientists are a little worried that some of the 600 spacecraft now in Earth orbit might get bumped -- hard.

The concern isn't so much about physical damage from collisions with space dust as about electronic mischief, the researchers said.

Sudden contact with even very tiny dust grains might generate electric pulses strong enough to disrupt electronic equipment aboard a satellite.

It could be bad enough to knock a satellite out of action.

On the ground there is little danger; the dust specks burn quickly once they enter the air.

But satellites orbiting above Earth's atmosphere are essentially unshielded, and not much can be done to make them less vulnerable.

Possible defense tactics include turning the power down during the meteor shower to avoid electrical damage, and rotating the spacecraft so vulnerable parts, such as solar panels, present less surface to the shower.

There are about 600 active satellites in Earth orbit, many of them military, and each has its own set of vulnerabilities.

They also have become increasingly important for numerous ground-based activities, such as the navigation of ships, planes, cars and even people using the 24-satellite GPS, or Global Positioning System.

"In the last 30 years, people have developed a strong dependence on a variety of satellite services," said Peter Brown, a space scientist at the University of Western Ontario, in Canada.

"Unfortunately, if even one satellite was disabled in the storm, it may not only be a multimillion-dollar disaster for its owners, but may disrupt services for millions of clients."

A good example of dependence on satellites was the loss of communication in May with a satellite that handles much of the nation's electronic paging.

In an instant, millions of people were left out of touch with their home offices, some doctors could not be reached and commercial services were disrupted.

In trying to be prepared for the event (which is expected to be at its brightest and most active Nov. 17), Brown and a team of other Canadian scientists, working with the Center for Research in Earth and Space Technology in Toronto, have created an organization devoted to working to reduce the odds that satellites will be damaged.

Efforts are being coordinated with the U.S. Space Command, the European Space Agency and the Canadian Space Agency, plus commercial and military organizations.

According to astronomer Brian Marsden of the International Astronomical Union's central telegram bureau in Cambridge, Mass., there is no way to predict accurately how "strong" the Leonid meteor shower will be.

"It's very chancy whether there will be a 'storm' or just a fair number" of meteors, Marsden said.

"There probably will be some; it would be surprising if there were none at all.

"But is it worth losing sleep over? I'm inclined to say no."

He added that comet Tempel-Tuttle "was discovered in 1865, just a few months before the really great [meteor] display of 1866."

The comet circles the sun once every 33 years, so it is classified as a short-period comet.

"It has really been Old Faithful," Marsden said.

Pub Date: 11/04/98

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