Astronomy and Astrophysics – Astronomy
Scientific paper
Sep 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995metic..30..602w&link_type=abstract
Meteoritics, vol. 30, no. 5, page 602
Astronomy and Astrophysics
Astronomy
Eureca, Micrometeorites, Space Debris
Scientific paper
The European Retrievable Satellite (EURECA) was in orbit at an altitude of 500km for 11 months. After recovery, the multi-layer thermal insulation blankets (MLI) covering the craft were removed and scanned for signs of micrometeoroid impacts. A total of ~29m^2 of the blankets was surveyed, (~37% of the surface) [1]. Further examination indicated that there were 59 penetration features, ranging in diameter from ~1200 micrometers down to ~60 micrometers [2]; holes of smaller dimensions cannot be detected in MLI, due to the structure of the topmost surface (beta-cloth, made from woven fibres of Teflon-coated glass fibre. a Si-, Al- and Ca-rich material). We have now completed EDAX-SEM analysis of residual material associated with the impacts, and have attempted to classify the residues and thus ascertain the relative proportions of holes produced by natural micrometeoroids and space debris. The multi-layered nature of the blankets allowed impacting particles to decelerate progressively and thus be captured. Particles were readily detected within most blankets, and individual penetration features often contained many particles, frequently with differing compositions, and at various levels within the blanket structure. Particles were not always close to an impact feature. In Type 6 MLI, (the most common blanket-type on EURECA, with 22 layers), there is a positive correlation between the diameter of the impact hole in the beta-cloth and the number of layers subsequently penetrated (mainly Al foil). This observation is consistent with the largest holes being made by the particles with the highest energy. The criteria used to assess the possible origins of the residual material were those of Zolensky et al. [3]. Analysis (see table) indicated that 7% of the particles were natural micrometeoroids, and 43% were pieces of beta-cloth carried into the intenor of the blankets as a result of impacts. The remainder was space debris. Normalizing the analyses to a "per hole" basis, S impacts were produced by natural micrometeoroids and 20 by space debris. The remaining 34 holes could not be assigned a specific origin. Space debris occurred as paint flakes, rocket propellant, fragments of electronic components and spacecraft materials, in addition to inorganic salts, possibly from astronaut waste. The search for residues of natural origin was hampered by the presence of shattered fragments and melted pieces of beta-cloth. The material believed to be of possible natural origin was present as Mg-silicate (at 2 sites), and one occurrence each of Fe, Mg-silicate, Ti, Al-silicate and Fe, Ni metal. It is clear from the results of this study that beta-cloth is not an ideal surface for the recovery of natural micrometeoroid debris for further investigation. References: [1] Aceti R. et al. (1994) ESA Bulletin, 80, 21-26. [2] Grady M. M. et al. (1995) LPS XXVI, 485-486. [3] Zolensky M. E. et al. (1993) LDEF--69 Months in Space, Second Post-Retrieval Symposium, 277-302.
Grady Michael
Sexton Adam
Wright Ian P.
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