Prototype Optical Sensor for CubeSat Attitude Determination with Air Bearing Validation

Abstract

State of the art CubeSats such as ExoplanetSat require pointing precision for the science payload on the order of arcseconds. ExoplanetSat uses dual stage control to achieve the pointing requirement. Reaction wheels provide coarse satellite attitude control while a high bandwidth piezoelectric stage performs fine optical stabilization. This paper discusses the development of ExoplanetSat's prototype optical system which serves dual roles as the payload and attitude determination sensor. A new fast star centroiding algorithm is developed based on centroid window tracking. The tracking algorithm utilizes centroid data from previous image frames to estimate the spacecraft slew rate which provides a prediction of the current centroid locations. An image window is centered at each predicted star location. A center of mass calculation is performed on the image window to determine the centroid location. This proposed algorithm is shown to reduce the computation time by a factor of 10 with a novel air bearing hardware testbed. This paper also develops a high fidelity optical imager model in MATLAB ® Simulink®. The air bearing testbed data provides confidence in the model results so that it can be used to complete future hardware trade studies.Downloaded by PURDUE UNIVERSITY on July 30, 2015 | http://arc.aiaa.org |