An online attitude determination filter is developed for a nano satellite that has no onboard attitude sensors or gyros. Specifically, the attitude of NASA Ames Research Center's O/OREOS, a passively magnetically stabilized 3U CubeSat, is determined using only an estimate of the solar vector obtained from solar panel currents. The filter is based upon the existing multiplicative extended Kalman filter (MEKF) but instead of relying on gyros to drive the motion model, the filter instead incorporates a model of the spacecraft's attitude dynamics in the motion model. An attitude determination accuracy of five degrees is demonstrated, a performance verified using flight data from the University of Michigan's RAX-1. Although the filter was designed for the specific problem of a satellite without gyros or attitude determination it could also be used to provide smoothing of noisy gyro signals or to provide a backup in the event of gyro failures.

No abstract

MIL-STD-499B "Systems Engineering" defines a disciplined design and verification process for developing new systems. It's iterative and balanced approach results in systems that meet all of their intended needs and satisfy all of their intended customers. Mature systems with well defined designs, established specifications. limited requirements traceability, and existing design and manufacturing processes are faced with a dilemma when addressing modifications and upgrades. Full implementation of MIL-STD-499B cannot be cost justified, while the absence of implementation results in stagnation of the program and a weakened competitive position.