Modeling collision probability for Earth-impactor 2008 TC3

Abstract We study the evolution of the Earth collision probability of asteroid 2008 TC 3 using a short observational arc and small numbers of observations. To assess impact probability, we use techniques that rely on the orbital-element probability density function characterized using both Markov-chain Monte-Carlo orbitalranging and Monte-Carlo ranging. First, we evaluate the orbitaluncertainties for the object from the night of discovery onwards and examine the collapse of the orbital-element distributions in time. Second, we examine the sensitivity of the results to the assumed astrometric noise. Each of the orbitsobtained from the MCMC ranging method is propagated into the future (within chosen time bounds of the expected impact), and the collision probability is calculated as a weighted fraction of the orbitsleading to a collision from the Earth. We compare the results obtained with both methods.