The Star Tracker 5000: A High-Precision Star Tracker and Attitude Determination System Jeffrey W Percival ([email protected]) Kurt P Jaehnig ([email protected]) Department of Astronomy University of Wisconsin - Madison The ST5000 is a low-cost star tracker and attitude determination system that has flown on 33 NASA Sounding Rocket flights (most recently on 21-Feb-2016, 36.297, PI France, CU), several flights on the WASP platform, and one night-time flight on a Near Space Corporation high-altitude balloon, during which it successfully performed many attitude determinations in the presence of a torsional oscillation. It performs its autonomous attitude determination quickly (last flight 0.7 seconds) and tracks with sub-arcsecond RMS error in each axis (last flight 0.7” in yaw and 0.8” in pitch). It routinely provides the sounding rocket program with reliable, precise pointing at a wide variety of targets, including lowsurface brightness galaxies, x-ray sources, comets, and even grazing occultations of bright stars by the Earth’s atmosphere. We are currently developing an entirely new hardware host for the flight-proven ST5000 software system. We have selected an Allied Vision Gigabit Ethernet camera with infra-red sensitivity and a small, highly-integrated single board computer. The CPU will be a small (4x5 cm), low-power (2W), fast (1GHz) host for the ST5000 software. The infra-red sensitivity, coupled a with blocking filter to eliminate solar scatted light, will allow daytime tracking on high-altitude balloons. We have performed night-sky testing in Madison with this camera in NIR mode with blocking filters, and have seen promising results in rejecting scattered light.