Collision orbits and phase transition for 2004 AS$_1$ at discovery

Abstract

Abstract. We evaluate asteroid orbital uncertainties from the discovery night onwards using 6D orbit computation tools based on statistical techniques. In particular, we outline a new nonlinear Monte Carlo technique of phase-space sampling that helps us in assessing the nonlinear phase transition from extended orbital-element distributions to well-constrained ones as the observational arc and number of observations grows. We apply the statistical techniques for near-Earth asteroid 2004 AS 1 to examine the time evolution of the orbital uncertainties and to assess the asteroid impact risk immediately after discovery. We start with the technique of statistical ranging for exiguous data, continue with the phase-space sampling technique for moderate data, and conclude with the standard least-squares fit for extensive data.

Spins, shapes, and orbits for near-Earth objects by Nordic NEON

“…During the course of the program (as of November 2006), four NEOs have been recovered, while improved orbits have been obtained for more than 76 objects. One of the followup objects was the PHO 2004 AS 1 whose drastic discovery-night prediction implied a possibility for a short-term (within 48 hours) Earth impact (Virtanen, Muinonen, Granvik et al (2005), ) but which was quickly ruled out with new observations. The newly developed VoV technique was tested and proved useful in the follow-up work.…”

Discovering Earth’s transient moons with the Large Synoptic Survey Telescope

“…Two of these objects are the aforementioned single-night cases, and five have S geo ą 98%. The sampled Keplerian orbit distribution of these objects is typically best described as being in the so-called orbital phase transition (Virtanen et al, 2005), where the resulting Keplerian orbit distribution is nearly, but not entirely Gaussian. An orbital solution was produced for all but one object with at least three detections within 15 nights.…”

Time evolution of orbital uncertainties for the impactor candidate 2004 AS1

“…is here assessed using two techniques, that of statistical orbital ranging (Ranging; and that of sampling in phase-space volumes of variation (VoV; Muinonen et al, 2006). For a summary of both techniques, we refer also to Virtanen et al (2005).…”

“…We expand the study initiated in Virtanen et al (2005), where we attacked the problem of impact risk assessment at the very moment of discovery. The ill-posedness of this problem stems from the inverse problem of computing the orbit from a small number of observations covering a short observational arc.…”