Microparticle Populations at LEO Altitudes: Recent Spacecraft Measurements

Abstract

Data from satellite impact experiments and the scanning of recovered spacecraft surfaces and solar cells offer an extended time base for examining, using a consistent methodology, microparticle fluxes at low Earth orbital (LEO) altitudes. Revised estimates of the ratio of natural micrometeorites to space debris at micrometer dimensions at ∼500 km altitude show that the debris population is not as dominant as previously believed. New data show that, despite a predicted growth in the debris population, the particle flux has not changed appreciably in this size regime over the period 1980–1994. Of penetrations of spacecraft surfaces of a 4 to 5 μm thickness 18 +9/ −6% are due to interplanetary meteoroids, whereas above ∼30 μm thickness the interplanetary component dominates. Results of studies of atmospheric drag depletion of orbital components, confirmed by flux data at differing altitudes, show that at altitudes of ∼240 km the meteoroid population dominates even at micrometer sizes due to the extremely short lifetimes of orbital particles. Exposure of detectors in such low orbits represents an opportunity to sample the interplanetary meteoroid population without contamination from space debris.