Getting More Performance From INTA NanoSat-1B Truncated Pyramid Sun Sensors

The National Institute for Aerospace Technology NanoSat-1B Earth orbiting satellite uses Sun sensors as part of the attitude determination and control system. The sensors have a truncated pyramidal structure with five solar cells. To simplify the work of the Sun sensors software, a new solar cell model is introduced. This model allows for a 160° field of view, and compared with the usual one is simpler and has a similar accuracy. This paper proposes a calibration procedure that estimates the direction of solar cells, once integrated in the truncated pyramid structure. In addition, this paper proposes a space qualification method, with the satellite in orbit. This method does not need a reference sensor, but instead it uses combinations of groups of solar cells to obtain data bands, so averaged results can be obtained. Combining the calibration and qualification procedures, the precision of the Sun sensor improves from the original ±7.5° to ±1.8°. With this precision, it was possible to extend the operational performance of the satellite.