Orbit estimation for late warning asteroid impacts: The case of 2014 AA

We describe a computational technique to assess the near-term Earth impact hazard posed by newly discovered asteroids. In these late warning cases the observational data sets will often include only an hour or so of tracking, leading to a severe degeneracy in the orbit estimation. The systematic ranging approach attacks this problem by exploring the poorly-constrained space of geocentric range and range rate, while the plane of sky position and motion is readily derived from the recorded observations. A raster scan in the two-dimensional range-range rate space allows us to identify regions corresponding to collision solutions, from which we derive rigorous impact probabilities, as well as potential impact times and locations. As an example, we shall consider the case of 2014 AA, a small asteroid that was discovered from Arizona by the Catalina Sky Survey early on January 1, 2014, and-as evidenced by infrasound monitoring-impacted the Atlantic Ocean less than a day later.