Digital Sun Sensor Design for Nanosatellite Applications

In this research a novel, semi-custom design of a Sun sensor, based on the orthogonal photodiode array design approach, applicable for nanosatellites and other small spacecraft is proposed. A common and well-known strategy of application of a geometrical aperture mask on the light detectors is improved upon and utilised in a non-conventional fashion in the design presented in this thesis. The main characteristic of this design, that is investigated in this work, is the inclusion of a chirped pattern of slits, while using a digital readout of the photodiode arrays. This pattern is expected to allow greater angle detection accuracy while digital photodiode readout decreases complexity and power consumption. The array based design approach is chosen due to lower power requirements, mass savings and simpler readout interface and signal processing in comparison to the matrix based approach. The Sun sensor design presented maximises the accuracy, while keeping the cost, development and implementation time and complexity to minimum. The design will be demonstrated on DESCENT mission CubeSat as a part of the Moth-Eye Anti-Reflective solar cell coating payload. The characterisation of the non-calibrated manufactured part shows that the sensor is capable of 1 degree accuracy, which is expected to improve to under 0.5 degrees with calibration and sensor data processing.