SATELLITE IMPACT PROBABILITIES: ANNUAL SHOWERS AND THE 1965 AND 1966 LEONID STORMS

Abstract—The stream meteoroid impact probability for space platforms is reviewed and found to be very low under normal circumstances. While the literature contains numerous accounts of spacecraft apparently suering damage and/or interference during meteoroid stream encounters, we find that there is, in fact, very little evidence to support such claims. This conclusion may not be valid, however, during meteor storms, when the flux of visual meteors can increase by factors in excess of 103 to 104 of that from the sporadic background. Special attention is directed towards the Leonid meteor storms of 1965 and 1966—the only meteor storms since the dawn of the space age. The space platform impact probabilities during the 1966 storm were small but none negligible, being of order 1 % for an exposed surface area of 2 m2 at a limiting meteoroid mass of 10ÿ7 g (and assuming a stream mass index s = 2.0). The circumstances surrounding the possible encounters of the Pegasus II and III, and Mariner 4 spacecraft with Leonid stream meteoroids are discussed in some detail. While the 1966 Leonid meteor storm is the strongest on record (in the sense of the highest visual meteor rates) no apparent meteoroid inflicted damage to a spacecraft can be unambiguously linked to it. This result is mostly a consequence of the small number and small size of spacecraft in Earth-orbit at the time of the 1966 storm. # 199