FINDING VERY SMALL NEAR-EARTH ASTEROIDS USING SYNTHETIC TRACKING

Abstract

We present an approach that significantly increases the sensitivity for\nfinding and tracking small and fast near Earth asteroids (NEA's). This approach\nrelies on a combined use of a new generation of high-speed cameras which allow\nshort, high frame-rate exposures of moving objects, effectively "freezing"\ntheir motion, and a computationally enhanced implementation of the\n"shift-and-add" data processing technique that helps to improve the signal to\nnoise ratio (SNR) for detection of NEA's. The SNR of a single short exposure of\na dim NEA is insufficient to detect it in one frame, but by computationally\nsearching for an appropriate velocity vector, shifting successive frames\nrelative to each other and then co-adding the shifted frames in\npost-processing, we synthetically create a long-exposure image as if the\ntelescope were tracking the object. This approach, which we call "synthetic\ntracking," enhances the familiar shift-and-add technique with the ability to do\na wide blind search, detect, and track dim and fast-moving NEA's in near real\ntime. We discuss also how synthetic tracking improves the astrometry of fast\nmoving NEA's. We apply this technique to observations of two known asteroids\nconducted on the Palomar 200-inch telescope and demonstrate improved SNR and\n10-fold improvement of astrometric precision over the traditional long exposure\napproach. In the past 5 years, about 150 NEA's with absolute magnitudes H=28\n(~10 m in size) or fainter have been discovered. With an upgraded version of\nour camera and a field of view of (28 arcmin)^2 on the Palomar 200-inch\ntelescope, synthetic tracking could allow detecting up to 180 such objects per\nnight, including very small NEAs with sizes down to 7 m.\n