Physical property requirements of a target asteroid for a mitigation demonstration mission

Kurzfassung

As part of the NEOShield project we are carrying out a statistical investigation of the properties of the known NEO population, using the latest published data, with the aim of estimating the most likely mitigation-relevant physical properties of the first threatening NEO to trigger a space-borne mitigation campaign. A major aim of NEOShield is to pave the way for a mitigation demonstration mission, including an appropriate and realistic choice of target NEO. Our investigation focuses on the physical properties of the most frequent serious impactors. We define a serious impactor to be one with the potential to lead to major loss of life and damage to infrastructure. At the low end of the size range our definition includes atmospheric events such as the 1908 Tunguska explosion, caused by a body with a diameter of around 50 m. We consider the upper limit of our diameter range of interest to be around 200 m: for objects above this size the impact frequency drops below 1 per 10 000 years. The small sizes of the NEOs in question present technical difficulties for mitigation planning. The complexity and chances of failure of a mitigation mission increase with decreasing diameter below a few hundred meters due to, e.g., the difficulties of targeting and maneuvering around an optically faint, low-gravity object. Further complications arise due to the fact that rotation rates and shapes tend to be more extreme in the case of such small NEOs. Very little is known about the mitigation-relevant properties of small NEOs. An important aspect of our study is to determine to what extent common assumptions about NEO physical properties are justified for mitigation planning, and identify the most critical areas of ignorance. We present and briefly discuss results obtained to date. Funded under EU FP7 program agreement no. 282703.