The vectorial photoelectric effect under solar irradiance and its application to sun sensing

TL;DR

This paper explores using the vectorial photoelectric effect in metal cathode detectors to improve sun sensor sensitivity for spacecraft attitude control, offering advantages like durability and reduced error from earth albedo.

Contribution

It introduces a novel sun sensing scheme leveraging the vectorial photoelectric effect, enhancing sensitivity and robustness over traditional cosine detectors.

Findings

Metal cathode detectors show high durability and minimal degradation.

The proposed design reduces errors caused by earth albedo.

Sensitivity optimization balances detection currents and measurement accuracy.

Abstract

Sun sensors are an integral part of the attitude and orbit control system onboard almost any spacecraft. While the majority of standard analogue sun sensors is based on photo-detectors which produce photo-currents proportional to the cosine of the incidence angle (cosine detectors), we propose an alternative scheme where the vectorial photoelectric effect is exploited to achieve a higher sensitivity of the sensed photo-current to the incidence angle. The vectorial photo-effect is investigated in detail for metal cathode detectors in a space environment. Besides long operational lifetimes without significant degradation, metal cathode detectors are insensitive to earth albedo, which may significantly reduce the errors affecting attitude measurements in low earth orbits. Sensitivity curves are calculated and trade-offs performed with the aim of optimizing the sensitivity whilst also providing currents sufficient for detection. Simple applications and detector configurations are also discussed and compared to existing designs.