Particulate Detection in the Near Earth Space Environment Aboard the Long Duration Exposure Facility Ldef: Cosmic or Terrestrial?

• Published in: International Astronomical Union Colloquium 1991, Vol.126, p.2-10
• Main Authors: McDonnell, J.A.M., Sullivan, K., Stevenson, T.J., Niblett, D.H.
• Format: Article
• Language: English
• ISSN: 0252-9211
• DOI: 10.1017/S0252921100066379

Examination of surfaces exposed for more than five and a half years, from detectors with unique attitude stabilisation relative to the orbital velocity vector, offers scope for examining definitively the sources of hypervelocity space particulates. Surfaces reveal discrete crater morphologies, crater size distributions and incident flux distributions. Discrete crater studies will later also reveal the chemistry of residues which can, especially via the capture cell principle, lead to elemental analysis of micron dimensioned particles. First analyses of the flux data from the thin foil perforation experiments (MAP) involve a study of the statistics of the forward (ram) direction, the rear (trailing) direction and the space pointing direction. Modelling of the dynamics of geocentrically bound and unbound orbits yields evidence that the characteristics of the particles, and hence probably their source, change over the particle size range measured by the experiment. Smaller particles (< 1 μm diameter) have lower velocities which could include geocentrically bound particulates, whereas the larger particles (5-10 μm diameter) can be identified with “cosmic” particles of interplanetary or interstellar origin.