The Leonids meteor shower 2002

This are the texts from press releases from the SES-Astra and Eutelsat web sites. Spacecraft are at risk from cosmic debris - the decommissioned, and long out of service Cosmos 539 was damaged on April 21st 2002 after being struck by space junk. Its orbit was altered, and part of the spacecraft broke off....

SES Astra

The Leonids is an annual meteor shower that occurs in November of each year. It is caused by the remnant particles of the comet Temple-Tuttle, whose path is crossed by the Earth on its orbit around the sun. The majority of these particles are expected to be approximately the size of a grain of  sand. The 2002 Leonid meteor shower is predicted to occur between 1:00 and 16:00 UT on Tuesday November 19, 2002, with two intensity peaks at around 4:00 UT and 10:45 UT.

Orbiting spacecraft are exposed throughout the year to micrometeoroids which impinge upon the Earth at all times. During the Leonid shower, however, the density of particles is significantly higher. Additionally, the Leonids move at higher velocities than ordinary micrometeoroids. SES ASTRA estimates that the probability of a particle collision with any of the ASTRA satellites is extremely low at approximately 0.1%. No Leonid-related incident has been reported on any ASTRA satellite in the past. However, SES ASTRA will take all reasonable risk mitigation measures to ensure full operability of the satellites and full transponder service during the event.

Spacecraft maneuvers and other discretionary commanding are scheduled at least one day away from the encounters. Prior, during and after the main Leonids encounter peaks, contacts with observers are monitored to verify that the predictions being worked to are indeed correct. During the main Leonids shower intensity peaks extra technical staff will be on hand at the ASTRA Satellite Control Facility to allow quick response should any spacecraft control state, attitude or power upsets occur. ASTRA satellites feature onboard redundancy and back-up systems for all critical spacecraft functions.

SES ASTRA does not anticipate any unusual activity occurring on the satellites as a result of the Leonid meteors. We will continue to review and analyze any relevant information that becomes available and advise our customers of any major update.

Eutelsat

Background information
In November of each year, the Earth passes through the debris cloud from the comet Temple-Tuttle. This event generally creates a meteor shower as the dust enters the Earth's atmosphere and burns up. Since the debris appears to come from the direction of the constellation Leo, the meteor shower is called the "Leonid shower".
The 2002 Leonid meteor shower is predicted to take place on November 19, beginning shortly after midnight. The activity period of the shower is expected to last into the afternoon, with predicted high levels of activity (varying from around 3,000-10,000 ZHR) at about 04.00 and 11.00 UTC.

Potential risks
The potential effects caused by the Leonid shower could be both mechanical and electrical, although the probability of any physical damage is very low. The electrical effects could be due to the production of charged plasma clouds and induced voltages, leading to electro-static discharges in the satellite. It should be emphasised that satellites are exposed throughout the year to the effects of micrometeoroids (in the form of dust particles), although during the shower the velocity and density of particles is significantly higher.

Eutelsat's strategy to minimise any possible risks to service
Eutelsat is taking several measures in order to protect its satellite fleet from the Leonid meteor shower, while maintaining service continuity and without any impact on operational traffic.
These measures include

• Minimising surface area exposed to the flux of the Leonids by adjusting the angle of the arrays where appropriate taking into account the design of the satellites.
  
• Avoiding any unnecessary spacecraft commanding activity close to and during the expected peaks of the Leonid flux.
  
• Close observation of the actual observed flux density during the passage based on available earth observations.
  
• A reinforcement of the in-orbit support from the operations engineering staff in order to ensure an extensive monitoring of Eutelsat's satellites during the event (in particular with respect to electrical subsystems).
  

These careful measures to reduce the shower's possible impact on Eutelsat's satellites, which have extensive on-board redundancy, have shown their efficiency in the past. The last Leonid meteor showers had no known effects on Eutelsat's fleet.

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