Comet may soon harm satellites

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-November, 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.

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 year's encounter may be the most intense in 33 years.

So space scientists are a little worried some of the 600 spacecraft now in Earth's 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, conceivably, 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.

At present, there are about 600 active satellites in Earth's orbit, many of them military, many civilian, and each with its own set of vulnerabilities.

11-04-98