PhAst: An IDL Astronomical Image Viewer Optimized for Astrometry of Near Earth Objects

We present PhAst, a new IDL astronomical image viewer, based on the existing ATV application, which has been optimized for astrometry of Near Earth Objects (NEOs). After describing the features of PhAst, we describe how PhAst enabled the recovery of the Virtual Impactor (VI) 2011AX22 and the Potentially Hazardous Asteroid (PHA) 2008OX1. The recovery of 2011AX22 led to a large improvement in the time of perihelion passage and in the semimajor axis and eccentricity of its orbit. The distance of closest approach in May 2055 was moved away from Earth to >1 lunar distance. As a result of the orbital improvement made possible by the successful recovery, NEODyS downgraded 2011AX22 from a VI to a PHA, having ruled out the chance of an Earth impact this century. The recovery of 2008OX1 extended its observational arc to 1303 days—more than 2.5 orbital revolutions. It was confirmed to be a PHA and its orbit was improved sufficiently to permit prediction of its sky position to within 1'' over an interval of 10 years into the future. We discuss the astrometric and photometric performance of PhAst and then conclude by briefly describing future enhancements to the application.