UC Santa Cruz

Very small spacecraft, called SmallSats, CubeSats, and NanoSats, have become very popular due to their low-cost, complexity, and availability of launch platforms (as extra payloads). These small satellites enable a future of low-cost satellite constellations to accomplish various space missions. The Generalized Nanosatellite Avionics Testbed (G-NAT) lab at NASA Ames Research Center in collaboration with UC Santa Cruz has developed a laboratory to verify sensor and actuator performance requirements of CubeSats in a standardized testing facility equipped with an ultra low-cost attitude truth system based on a camera tracking of visual fiducials. This work rst developed ultra low-cost real-time streaming attitude truth system that is self-calibrating, portable and scalable. The attitude truth system is cross-platform and can be used at various CubeSat testing facilities to track to CubeSat attitude (angular and translational position in the inertial reference frame). Attitude truth system accuracy and robustness improvements were made to rectify highly variant attitude observations during quick maneuvers using an extended Kalman filter. The attitude truth system, implemented with the extended Kalman lter, was able to sustain estimation standard deviation values of +/- 1.30 degrees, +/- 1.30 degrees, and +/- 0.61 degrees in roll, pitch and yaw, respectively. The finalized truth system with the extended Kalman lter was used as validation for testing and verification of on-board CubeSat attitude estimation. Two attitude estimation algorithms explored, were TRIAD (Tri-Axial Attitude Determination) and the complementary filter. Both algorithms were implemented using low-cost IMU sensors and solar photodiodes on a CubeSat testbed. The tests verified that the complementary filter algorithm is more accurate than TRIAD using the same sensor suite when measured by the attitude truth system; the complementary filter performed better than TRIAD by 3.3 degrees, 3.3 degrees and 2.6 degrees in roll, pitch and yaw, respectively according to the attitude truth system with extended Kalman filter.