ISRO is taking precautionary measures to safeguard its satellites during the Leonid Meteoroids shower which is expected to reach its peak between 2.30 pm and 3.30 pm and again between 10.30 pm and 11.30 pm on November 18, 2001. For the Indian Remote Sensing Satellites, the precautionary measures include suspending the camera operations, arresting the camera steering mechanism and switching off the solid state recorders for about 10 hours during the peak of Meteoroids shower. In the case of INSAT satellites, the solar arrays will be oriented in such a way that they offer minimum surface area to the Meteoroids shower. The Gyros on board these satellites will be kept continuously on to detect any disturbances due to Meteoroids impact and in case of any disturbances, the satellites will be brought back to their proper orientation using reaction control thrusters on board.
Designers of the various satellite subsystems will be on the alert to help in taking contingency measures in case of any impact of meteoroids on any of the satellites.
It may be noted, however, that the probability of meteoroids hit on the IRS satellites, which are in the near earth polar orbits, is only about 0.013 percent and for INSATs which are in the geo-stationary orbit, it is around 0.035 percent. At present, ISRO has five satellites in operation (IRS-1C, IRS-1D, IRS-P3, IRS-P4 and TES) in the Polar sun-synchronous orbits and five satellites (INSAT-2C, INSAT-2DT, INSAT-2E, INSAT-3B and GSAT-1) in the geo-stationary orbit.
Every 33 years, the Leonid Tempel Tuttle makes its closest approach to the sun and, when in proximity to the Sun, the sublimation of its ice and dust content results in the spewing of low density debris. These tiny particles seem to emanate from the constellation of Leo and hence the name Leonid Meteoroids. What makes Leonid shower unique is its hyper velocity motion. The Earth, while orbiting the sun, invariably crosses this stream every year and the meteoroids can cause damage to the satellites like pitting of solar cells, optical surfaces and mirrors or even causing ruptures. They can also cause electrical damages induced due to the plasma cloud created by the hyper-velocity impact of meteoroids disturbing the highly sensitive microprocessors of satellites.
Space agencies all over the world take precautions to safeguard their spacecraft. Even though the Leonids shower has affected none of its satellites so far, ISRO has planned to take all possible precautions for protecting its satellites from the ensuing Leonids shower on November 18, 2001.
