External Verification of CubeSat Using AprilTag Visual Fiducials and an Extended Kalman Filter

摘要

Very small spacecraft, such as CubeSats, have become very popular due to their low-cost, low-complexity, and of launch platforms (as secondary 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 the ability to verify sensor and actuator performance requirements of CubeSats using an ultra low-cost attitude truth system based on visual fiducials. In this work, a real-time streaming AprilTag attitude truth system is developed that is portable, scalable and easily calibrated based on an AprilTag external conjugate. The attitude truth system is cross-platform and can be used at various CubeSat testing facilities to track CubeSat Euler angles, angular rates and body rates. Accuracy and robustness improvements were made to the AprilTag based attitude truth system to rectify noisy attitude observations during quick maneuvers using an extended Kalman filter based on Euler angular rate differential equations.