The Foresail-2 mission demands an enhanced radiation-tolerant sun sensor to withstand the high-radiation environment encountered in its Geostationary Transfer Orbit (GTO). The Analog Sun Sensor Array (ASSA) is developed to fulfill this requirement, providing attitude determination with an accuracy better than 1°. Traditional analog sun sensors, reliant on position-sensitive diodes (PSDs), encounter challenges such as distinguishing Albedo and celestial bodies like the Moon from the Sun, resulting in an in-orbit accuracy limitation of approximately 5°. ASSA utilizes four individual PSDs, each housed in a separate chamber equipped with its own pinhole to expand the field of view, thereby overcoming previous limitations. This design has built in triple hot redundancy. By using a STM32 controller and sufficient shielding the sensor can be used in high radiation environments.
Anger et al. (2025) studied this question.