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UBC Theses and Dissertations

The orbital distribution of near-Earth objects inside Earth's orbit Greenstreet, Sarah


Canada's Near-Earth Object Surveillance Satellite (NEOSSat), set to launch in early 2012, will search for and track Near-Earth Objects (NEOs), tuning its search to best detect objects with semimajor axis a<1.0 AU. In order to construct an optimal pointing strategy for NEOSSat, we needed more detailed information in the a<1.0 AU region than the best current model (Bottke et al., 2002) provides. We present here the NEOSSat-1.0 NEO orbital distribution model with larger statistics that permit finer resolution and less uncertainty, especially in the a<1.0 AU region. We find that Amors =30.1 ± 0.8%, Apollos =63.3 ± 0.4%, Atens =5.0 ± 0.3%, Atiras (0.718<Q<0.983 AU) =1.38 ± 0.04%, and Vatiras (0.307<Q<0.718 AU) =0.22 ± 0.03% of the steady-state NEO population, where Q is the orbit's aphelion distance. Vatiras are a previously undiscussed NEO population clearly defined in our integrations, whose orbits lie completely interior to that of Venus. Our integrations also uncovered the unexpected production of retrograde orbits from main-belt asteroid sources; this retrograde NEA population makes up ≃0.10% of the steady-state NEO population. The relative NEO impact rate onto Mercury, Venus, and Earth, as well as the normalized distribution of impact speeds, was calculated from the NEOSSat-1.0 orbital model under the assumption of a steady-state. The new model predicts a slightly higher Mercury impact flux.

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