Spin-Axis Attitude Determination from Earth Chord-Angle Variations for Geostationary Satellites

Spin stabilization offers a straightforward and robust concept for spacecraft attitude control. The spin-axis attitude determination is usually accomplished by means of sun- and Earth-sensor measurements. This paper explores techniques for spin-axis attitude determination using only Earth-sensor data. An immediate attitude determination can be achieved by straightforward geometrical arguments based on the extremes of the chord-angle variations over the orbit Furthermore, an effective least-squares approach is presented that employs a number of equidistant chord-angle measurements collected during one orbital revolution. The adopted measurement model is favorable for reducing the adverse effects of systematic errors. Finally, a few explicit approaches are offered for reconstructing the most important biases. The application of these techniques is illustrated by means of actual telemetry data from the METEOSAT second-generation satellite MSG-2.