Systematic ranging and late warning asteroid impacts

TL;DR

This paper introduces a systematic ranging technique for rapid orbit determination of newly discovered asteroids, especially useful for short observation windows, to assess impact risk with Earth.

Contribution

The paper presents a novel orbit determination method that efficiently assesses impact probability from limited observational data by scanning poorly-constrained parameters.

Findings

Effective in identifying impact solutions for recent asteroid cases

Provides probabilistic impact assessment from short observation arcs

Demonstrated success with 2008 TC3 and 2014 AA impactors

Abstract

We describe systematic ranging, an orbit determination technique especially suitable to assess the near-term Earth impact hazard posed by newly discovered asteroids. For these late warning cases, the time interval covered by the observations is generally short, perhaps a few hours or even less, which leads to severe degeneracies in the orbit estimation process. The systematic ranging approach gets around these degeneracies by performing a raster scan in the poorly-constrained space of topocentric range and range rate, while the plane of sky position and motion are directly tied to the recorded observations. This scan allows us to identify regions corresponding to collision solutions, as well as potential impact times and locations. From the probability distribution of the observation errors, we obtain a probability distribution in the orbital space and then estimate the probability of an Earth impact. We show how this technique is effective for a number of examples, including 2008 TC3 and 2014 AA, the only two asteroids to date discovered prior to impact.