[meteorite-list] Leonids May Short Satellites

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:49:02 2004
Message-ID: <200109241611.JAA14172_at_zagami.jpl.nasa.gov>

http://www.nature.com/nsu/010927/010927-5.html

Leonids may short satellites

November's shooting star shower could cause communications havoc.

Nature Science Update
PHILIP BALL
September 24, 2001

This year's Leonid meteor shower will be so big it poses a threat to the
thousands of satellites orbiting Earth. At least one satellite could be
shorted out when the Earth passes through the dusty trail of the comet
Tempel-Tuttle, astronomers predict.

Between 17 and 19 November there will be almost ten meteors per square
kilometre of sky - that's ten times more than in 1999, the most spectacular
of recent showers. So say Peter Brown of the Los Alamos National Laboratory
and Bill Cooke of NASA's Marshall Space Flight Center in the USA1.

The Leonids are Tempel-Tuttle's debris. The comet sweeps through the inner
Solar System every 33 years. These particles, mostly smaller than a grain of
sand, burn up brightly as they stream through the Earth's atmosphere at
around 150,000 miles an hour.

"A direct impact of even a single grain of dust could be catastrophic for a
satellite," explains Mark Bailey of the Armagh Observatory, Northern
Ireland. "The particle would vaporize when it struck, creating a plasma," he
says. "This cloud of electrically charged gas could short-circuit the
satellite's delicate electronics".

On the trail

The comet's dust trail takes centuries to disperse. Meanwhile the Earth
passes through the dust on its yearly orbit around the Sun. Each return of
the comet leaves a trail in a slightly different position, so our planet can
encounter several streams in different stages of dissolution in close
succession.

We enter the dust streams end-on so the meteors seem to issue from a single
point in the sky, superimposed on the Leo constellation: hence their name.
This year's Leonid shower will have two activity peaks.

At around 12.00 GMT on 18 November the Earth will pass through streams left
behind in 1766 and 1799. About five hours later we will hit streams from
1866, 1833 and three fainter ones from the seventeenth century.

It should be a spectacular show; but it is hard to predict how spectacular.
As the comet trails get older, their exact location becomes more difficult
to estimate. The first accurate Leonid activity prediction was made in 1999:
the shower produced over 3,000 visible meteors per hour.

Brown and Cooke have estimated how the dust streams disperse over time, for
a range of possible initial states. From observations of previous Leonid
showers, they try to determine which of these initial states is the best
guess. They calculate that the dust streams are broader and more dispersed
than older 2001 forecasts predict, so the showers may be longer but less
intense.

[Image][Image]
References

  1. Brown, P. & Cooke, B. Model predictions for the 2001 Leonids and
     implications for Earth-orbiting satellites. Monthly Notices of the
     Royal Astronomical Society, 326, L19 - L22, (2001).
Received on Mon 24 Sep 2001 12:11:39 PM PDT