Abstract
Short-arc orbit determination is crucial when an asteroid is first discovered. In these cases usually the observations are so few that the differential correction procedure may not converge. We developed an initial orbit computation method, based on systematic ranging, which is an orbit determination technique that systematically explores a raster in the topocentric range and range-rate space region inside the admissible region. We obtained a fully rigorous computation of the probability for the asteroid that could impact the Earth within a few days from the discovery without any a priori assumption. We tested our method on the two past impactors, 2008 TC3 and 2014 AA, on some very well known cases, and on two particular objects observed by the European Space Agency Gaia mission.
Highlights
Short-arc orbit determination is a very important step when an asteroid is first discovered
We are setting up a service dedicated to scanning the Minor Planet Center NEO Confirmation Page4 (NEOCP)
We denote as nonsignificant cases the objects for which there are less than three observations or the arc length is less than 30 minutes, unless there exists a nominal solution with a geodesic curvature signal-tonoise ratio (S/N) greater than 1
Summary
Short-arc orbit determination is a very important step when an asteroid is first discovered. Muinonen & Bowell (1993) defined a Gaussian probability density on the orbital elements space using the Bayesian inversion theory They determine asteroid orbital elements from optical astrometric observations using both a priori and a posteriori densities; the latter were computed with a Monte Carlo method. Ranging methods have been developed over the years to replace or refine the Monte Carlo approach in the short arc orbit determination. The weights of each set of orbital elements are based on a posteriori probability density value and the MCMC rejection rate These authors have developed this method for the European Space Agency (ESA) Gaia mission, in the framework of Gaia alerts on potentially new discovered objects by Gaia (see Tanga et al 2016).
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