SENPAI: Sidereal Enriched Rate-track Astrometry in Deep Imagery of Solar System Bodies

Abstract Rate-track imagery−in which a telescope tracks an object’s proper motion instead of the stellar background−has long been used to enhance the signal-to-noise ratio of faint solar system bodies such as asteroids, comets, and artificial satellites. Images from such observations are characterized by point source targets and streaked stars. While astrometric plate solving−matching ubiquitous and unique star fields to a world coordinate system−is a mature field of research, the complexities of detecting and measuring the centroid of star streaks in rate track imagery decreases astrometric accuracy. This is unfortunate, given that defining and refining orbits of bodies of the solar system require accurate astrometric positions. In this work, we propose a novel observing methodology for experiments requiring the enhanced signal-to-noise ratio of rate track imagery and the astrometrics of orbiting solar system bodies by capping rate track sequences with a sidereal observation at the tracked object’s position. The resulting data provide high-precision astrometry and a natural filter for detecting star streaks in the rate-track imagery. We demonstrate astrometric uncertainties in right ascension and declination of ≤1 . ″ 38 and ≤0 . ″ 96, respectively, on observations of calibration satellites using telescopes with pixel scales (instantaneous field’s of view) of 0 . ″ 90–1 . ″ 68. This technique−Sidereal ENriched Precision Astrometric Intelligence (SENPAI)—is designed to run automatically, requires no tuning or calibration frames on a per sensor basis, and throughput exceeds 85% on most sensors tested. SENPAI far exceeds the threshold requirement of ≤3 . ″ 0 of uncertainty in object positioning for initial determination of—and state updates to—the orbits of artificial satellites.