We recently submitted a design paper on the attitude determination subsystem of the RAX-1 and RAX-2 satellites to the journal Acta Astronautica. This subsystem was custom developed by MXL, and it utilizes magnetometers, photodiodes, rate gyroscopes, and an extended Kalman filter to achieve better than 5 degree angular accuracy. The paper covers the complete design of the subsystem and will be helpful for other satellite development teams. The paper will now undergo a peer-review process before being published.
The abstract to the paper is as follows:
The Radio Aurora Explorer (RAX) is a triple CubeSat that launched on November 19, 2010. RAX was designed to study plasma irregularities in the polar lower ionosphere (80-300 km), and is the first satellite mission funded by the United States National Science Foundation. The scientific mission requires attitude knowledge within 5 degree (1-σ), and a custom attitude determination subsystem was developed for the mission. The subsystem utilizes rate gyros, magnetometers, coarse sun sensors, and an extended Kalman filter. In this paper, we describe the design, implementation, and testing of the RAX attitude determination subsystem, including derivation of the determination requirements, sensor selection, the integrated hardware design, pre-flight sensor calibration, and attitude estimation algorithms. The paper is meant to serve as a resource for others in the small satellite and nanosatellite communities, as well as a critical reference for those analyzing RAX data. Lessons learned from the design and performance of the RAX determination subsystem will be used in future designs of attitude determination systems for small satellites and similar platforms, such as high altitude balloons and autonomous aerial vehicles.