Meteoroid morphology and densities: Decoding satellite impact data

The densities of interplanetary micrometeoroids have been inferred by various techniques in the past; a valuable (albeit indirect) technique has been the study of the deceleration profile of radar meteor trails, for example. Impacts on the thin foils of the Micro-Abrasion Package on NASA's LDEF satellite and the Timeband Capture Cell Experiment on ESA's Eureca satellite now provide direct in situ measurement of the cross-sections diameters of impacting micrometeoroids and also of space debris particles. Combining these data with impact data from thick-target impact craters, where the damage is mass-dependent, and where such targets have experienced a statistically identical flux, leads to a measure of the impactor density which is only weakly affected by the assumed impact velocity. Comparing the space result with those from simulations shows that the density distribution of interplanetary particles in space has a more significant low density component than the distributions obtained by most other recent methods and that the mean density is in the range 2.0 to 2.4 g cm(-3) for masses of 10(-15) to 10(-9) kg. The characteristic density - namely, the single value which would characterize the impact behavior of the distribution-is 1.58 cm(-3). Perforation profiles reveal that a large fraction of the largest particles impacting the satellites are nonspherical but that typical aspect ratios are mostly in the range 1.0-1.5. Flux distributions of the meteoroid population incident on the Earth at satellite altitudes are derived in terms of mass and mean diameter. (C) 1998 Academic Press.