Statistical and numerical study of asteroid orbital uncertainty

Abstract

Context. The knowledge of the orbit or the ephemeris uncertainty of asteroids presents a particular interest for various purposes. These quantities are, for instance, useful for recovering asteroids, for identifying lost asteroids, or for planning stellar occultation campaigns. They are also needed for estimating the close approach of near-Earth asteroids, and the subsequent risk of collision. Ephemeris accuracy can also be used for instrument calibration or for scientific applications. Aims. Asteroid databases provide information about the uncertainty of the orbits and allow the measure of the quality of an orbit. This paper analyses these different uncertainty parameters and estimates the impact of the different measurements on the uncertainty of orbits. Methods. We dealt with two main databases, astorb and mpcorb, that provide uncertainty parameters for asteroid orbits. Statistical methods were used to estimate orbital uncertainty and to compare them with parameters from the databases. Simulations were also generated to deal with specific measurements such as the future Gaia mission or present radar measurements. Results. Relations between the uncertainty parameter and the characteristics of the asteroid (orbital arc, absolute magnitude, etc.) are highlighted. Moreover, a review of the different measuments are compiled and their impact on the accuracy of the orbit is also estimated.

The Effect of Parallax and Cadence on Asteroid Impact Probabilities and Warning Times

“…These impact warning systems are based on a geometric sampling technique, for which the identification of the virtual impactors (VI) is performed on the line of variation (LOV; Milani et al 2005b), thus avoiding the poor efficiency inherent to the Monte Carlo methods, especially when the collision probability is small. Impact predictions are extremely sensitive to the orbit accuracy, which depends on many factors, but the primary drivers are the length of the observational arc and the astrometric accuracy of the detections (e.g., Desmars et al 2013). The longer the arc, and the better the astrometry, the more accurate the orbit.…”

Astrometric asteroid masses: a simultaneous determination

“…This will enable the determination of the masses of about 150 individual asteroids from close encounters, ∼100 with an accuracy of ≤ 50% and ∼50 with an accuracy of ≤ 10% (Mouret et al 2008). The Gaia star catalogue will enable the reduction of future, and the re-reduction of old observations with a very high level of accuracy (about 10 mas, see Desmars et al 2013), thus considerably increasing the accuracy of simultaneous asteroid mass determinations.…”

Post mitigation impact risk analysis for asteroid deflection demonstration missions

“…The lower limit is due to current GNC targeting capabilities. Taking into account the aforementioned criteria, a list of potential targets was constructed yielding rendez-vous delta-v < 6 km/s, absolute magnitude (H) derived sizes between 100-350 m and current ephemeris uncertainties (CEU) < 30 00 (Bowell, 2014;Desmars et al, 2013). Out of this set, 5 potential targets were selected.…”