The Spacewatch Project:  Unveiling the Origins of Near Earth Objects

Robert Jedicke
University of Arizona

In the past 20 years the Spacewatch Project at the University of
Arizona's Lunar and Planetary Laboratory has discovered over 235 Near
Earth Objects (NEOs).  We have modelled the observational selection
effects for the survey, and performed a 4-dimensional $(a,e,i,H)$
maximum-likelihood fit to the observed distribution for a linear
combination of expected orbit distributions of NEOs from each of five
possible sources ($\nu_6$ and 3:1 resonances, outer main belt,
Mars-crossing asteroids and Jupiter Family Comets).  The bias-corrected
model of the orbit distribution of NEOs thus obtained provides a wealth
of information on their population including injection rates into each
source region, their steady-state populations, number of NEOs in the
current population from each source.  This is the first
4-dimensional orbit distribution of the NEOs and it enables studies of
their albedo distribution, the expected number of Earth trojans and the
efficiency of existing and proposed NEO surveys.  I will discuss
our method of obtaining the model NEO orbit distribution and then
present the results of simulations of asteroid surveys