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(meteorobs) The Leonid Meteoroid Storm: INTELSAT's Risk Mitigation Strategy
[Extracted from INTELSAT website. Images supporting this article are
available at http://www.intelsat.int/cmc/info/leonids.htm]
INTELSAT
3400 International Drive, NW
Washington, DC 20008-3098
USA
The Leonid Meteoroid Storm: INTELSAT's Risk Mitigation Strategy
The Leonid meteoroid stream is one of the most famous streams in history.
To date the most severe Leonid meteoroid storm occurred in 1966 where the meteor
Zenith Hourly Rate (ZHR) was close to 100,000 per hour. The perigee return of
parent comet Tempel-Tuttle to the sun in early 1998, close to Earth's orbit,
raises the possibility of strong meteor displays. The Leonid activity started
in 1997 and is expected to increase dramatically in 1998 and 1999. The storm
activity is expected on 17 November 1998 and 18 November 1999. Based on
geometric similarity to 1866 and 1932 meteoroid storms, the ZHR is expected
to be between 200 to 10,000 per hour. The storm is expected to last about two
hours with several hours of build-up and decline. The meteoroid storm will
be in a direction that is nearly a 90=B0 angle to the sun-line.
Potential Risks
Given the high velocity of the Leonid meteoroids, their impact is an order of
magnitude larger when compared with typical background sporadic meteoroids.
The impact on orbiting satellites could be both mechanical and electrical:
* Mechanical in that the Leonids could cause damage to the satellite
structures or components. However, based on available technical information,
INTELSAT estimates that the probability of such an event on any satellite is
very small (less than 0.02%).
* Electrical in that meteoroids disintegrating upon impact with the spacecraft
could generate a plasma cloud as a result of ionization. This could lead to
electro-static discharge (ESD) on adjacent surfaces.
Mitigation Strategy
INTELSAT is planning to take prudent precautions to safeguard its satellite
fleet from the meteoroid storm without interrupting any operational traffic.
INTELSAT's strategy in mitigating the risks posed by Leonids are fourfold,
and will be entirely transparent to customers:
1. Satellite solar arrays will be slewed (angled edge-on in the direction of
the oncoming meteoroids) to minimize the net impingement area. Fortunately,
as the storm direction will be almost at a right angle to the sun line, this
will entail slewing the arrays by only 10=B0 to 12=B0 for two to three hours.
INTELSAT estimates that this strategy alone will reduce the probability of
impingement by significantly decreasing exposed satellite surfaces.
2. All ESD safety precautions will be implemented and critical satellite
modes will be turned off or "safed" during this period to eliminate
uncommanded events or activations.
3. Satellite controllers and on-call engineers will be on full alert during
the height of the storm to address any contingencies. While the INTELSAT
satellite control center is always staffed 24 hours per day, INTELSAT will
have an increased number of staff on-site, who will be fully briefed on
procedures to follow in the unlikely event of an emergency.
4. INTELSAT will continue to maintain the close dialogue which it has been
entertaining with other owner/operators of satellite systems and academic
institutions, and will remain fully informed of possible protective measu
res.
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