Space Debris: Quantifying and Mitigating the Impact Hazard
Australian Centre for Astrobiology, University of NSW
Last modified: July 29, 2011
Techniques are described that enable formal assessments or quantifications to be made of the collision probabilities between small debris items and operational satellites in different characteristic orbits (i.e. various altitudes, inclinations, and eccentricities). Further, particularly hazardous orbit types for future planned payloads are highlighted; specific dangerous classes of debris identified; and the extremely low debris collision probabilities for some orbit types (e.g. geostationary orbits) calculated, indicating that for these the natural meteoroid flux dominates the overall impact probability. Such results have a wide range of implications, from informed choices of operational orbits, the case for debris limitation and mitigation, and also the availability of a strategy of plausible deniability in the case of anti-satellite warfare.
Results are also given for calculations resolved in terms of impact speed (scalar) but also impact velocity (vector), such that it is feasible to obtain assessments of the comparative likelihoods of impacts of differing energies upon different sides of a satellite. For example, if a satellite has a fixed ‘leading’ (ram) face and similarly ‘up’, ‘down’, ‘spaceward’, ‘earthward’ and ‘trailing’ faces, then probabilities of impacts and distributions of impact speeds (or impact energies) onto each face by the population of anthropomorphic debris can be derived. With such information in hand informed decisions may be made by satellite designers with regard to the amount of shielding that is appropriate, the positioning of susceptible components on and within the spacecraft, and so on.
Finally it is shown that not only is the Jindalee surveillance radar system operated by the Australian Defence Organisation the most powerful detector of meteors ever employed, but also it has properties that made it especially suitable for the identification of artificial meteors produced by infalling small (sub-millimetre) debris particles.