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J.S. Stuart, R.P. Binzel (MIT)
Recent estimates of the near-Earth asteroid (NEA) population constrain the size of the population as a function of absolute magnitude [1], [2]. However, the albedo distribution of the NEAs is poorly constrained. Therefore, the size of the NEA population as a function of diameter is poorly constrained. Others are attempting to model the albedo distribution of the NEAs by tracing them back to their origins in the main belt and applying the albedo distributions observed there [3]. Presented here is a complementary approach using direct observation of the NEAs. The shape of the NEA population (as a function of semi-major axis, eccentricity and inclination), as determined by LINEAR data [1] and by Spacewatch data [2], is used as input to a Monte-Carlo simulation to derive the discovery bias that results from the differing physical properties of the NEAs. The Monte-Carlo asteroids are checked against three years of pointing history from the LINEAR system to determine which asteroids would have been detected under various assumptions of size and albedo. This simulation combines a realistic representation of the observational geometry of asteroid detection with the effects of differing physical properties. An observational program to determine spectral types and albedos of NEAs introduces further bias into the observed distribution of spectral types and albedos. A second Monte-Carlo simulation, starting from the results of the first simulation, is used to estimate this additional observational bias. The result is a set of bias correction factors which can be applied to the observed fractions of NEAs of various sizes and spectral classes to obtain an estimate of the debiased fraction of NEA spectral types and a debiased albedo distribution.
[1] J. Stuart (2001) Science 294, 1691. [2] W. Bottke et al. (2000) Science 288, 2190. [3] A. Morbidelli et al. (2002) Icarus, in press.
This work was sponsored by NASA and by the Department of the Air Force under Air Force Contract F19628-00-C-0002. Opinions, interpretations, conclusions, and recommendations are those of the author and are not necessarily endorsed by the United States Air Force. The author obtains financial support from the Lincoln Scholars Program at MIT Lincoln Laboratory.
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Bulletin of the American Astronomical Society, 34, #3< br> © 2002. The American Astronomical Soceity.