Single antenna attitude algorithm for non-uniform antenna gain patterns

摘要

The objective of this research is to investigate a new method for improving the accuracy of single antenna attitude systems based on GPS signal strength measurements. To achieve this objective, a predictive GPS signal strength model is proposed and developed. The model consists of a precisely measured three dimensional receiving antenna gain pattern (as fitted to the spacecraft), the distance dependent path loss, the effects of the ionosphere, the GPS satellite transmitting antenna gain, and the variation in GPS satellite transmission power. Furthermore, an algorithm is developed to provide an estimate of single-axis attitude solution based on this predictive GPS signal strength model. The performance of this new algorithm is evaluated and compared against two other single antenna attitude approaches using ground data and flight data. Results show that the new single antenna attitude algorithm is capable of providing attitude accuracy of 10 deg rms for static terrestrial platforms with a zenith pointing antenna. Furthermore, 15 deg rms from the FedSat satellite negative velocity pointing antenna configuration has been achieved.