DETECTION OF EARTH-APPROACHING ASTEROIDS IN NEAR REAL-TIME

This paper describes a computer program which is detecting Earth-approaching asteroids in near real time. The detection software runs on a Solbourne workstation computer at the site of the 0.91 m Spacewatch Telescope of the Steward Observatory on Kitt Peak. During the dark half of the month a Tektronix TK2048 CCD is mounted at one of the two Newtonian ports and operated in drift-scanning mode. Asteroids are detected by making three successive scans of the same field of view. During the first and second passes, the software can recognize fast moving objects by the trails they leave in the image. During the third pass, a moving object is detected by the displacement of its position in the first two passes relative to its position in the third. During 2 months of trial observing with this system (19 nights in May and June of 1990, covering 150 square degrees) 304 asteroids were detected down to a limiting apparent magnitude for untrailed images of V = 20.5. A comparison of the observed angular rates of motion with predicted rates for known orbit types shows that these are mostly main-belt asteroids, but also include some Hungarias, Phocaeas, Hildas, and one probable Mars crosser. The system also detected Earth approachers 1990 HA and 1990 MF. A study of the Earth-approaching asteroid distribution shows that this CCD system will be able to detect these objects and identify them based on their rate of motion before they approach the Earth, when they are moving less than 0.4-degrees/d. The analysis also shows that the discovery rate of the fast-moving Earth approachers can be enhanced by moving the telescope rapidly across the sky. An approximately 2 m telescope designed for this purpose might discover Earth approachers at a rate 10 times greater than conventional techniques.