Particle lifetime studies in LEO for aerocaptured interplanetary dust

Space impacts retrieved to Earth, such as those on LDEF and EuReCa, have led to an unprecedentedly high definition of the impact environment in Earth orbit. This leads to (1) a penetration flux distribution (2) angular dependence of the flux (3) physical signatures of the penetration through thin films and (4) chemical evidence of impact residues. (C) 1997 COSPAR. Published by Elsevier Science Ltd. At micron dimensions, space retrieved surfaces show an "excess" flux, mainly when exposed to the leading (ram) direction, attributable to space debris or to micrometeoroids captured in Earth orbit. We present results of studies to determine the capture efficiency of the Earth to interplanetary dust and the dwell time of microparticles in eccentric orbits. Effects of the solar hour angle of the initial argument of perigee at capture are critical and, especially, the increase or decrease of atmospheric density at subsequent perigee passages due to solar heating cycles. Results will be presented of interest to the relative importance of space debris and of astrophysical sources.