A GPS-Based Attitude Determination System for Small Satellites

This paper presents a novel, GPS-based attitude determination system (ADS). Carrier-phase differential GPS (CDGPS) accurate to within centimeters enables magnetometer-level pointing accuracy. Employing three GPS antennas allows for the determination of three independent baseline vectors, which can be combined to yield a precise attitude solution. Both simulation data for a satellite in LEO and terrestrial field test data suggest subcentimeter level accuracy, yielding an instantaneous pointing accuracy of approximately 2 degrees. This high precision makes possible numerous navigation-sensitive applications, such as in-orbit inspection, construction, or repair. Such technology offers many advantages to a small satellite system. Most significantly, a GPS-based ADS offers a high performance-to-cost ratio and requires minimal calibration, providing an ideal solution for small satellites. CUSat, an entry into the University Nanosatellite-4 competition, is a technology demonstrator for GPSbased attitude determination and provides a pointing accuracy better than 5 degrees. The CUSat CDGPS‐based ADS provides a complete solution for high precision attitude determination and navigation with a simple interface and modular design