Breadboarding of optical attitude sensor for space application

The aerospace industry is currently trying to improve the performance of telecommunications satellites and one of the ways to do this is to increase the size of the reflectors, which are expected to be up to 5m in diameter. This increase, however, involves the use of large structures to connect the antenna to the main body of the satellite and, since the rods undergo deformations due to temperature gradients in space, a metrological system is required to know the attitude of the reflector. In this sense, INRiM (Istituto Nazionale di Ricerca Metrologica - National Institute of Metrological Research) proposes the use of optical metrology based on the exchange of information between the spacecraft and the antenna through light beams. This methodology makes it possible to obtain information through non-contact measurements using small and highly accurate instruments. The instrument designed by INRiM is called ATOM (ATtitude Optical Monitor) and is composed of an Active Unit (AU), which represents the reference system (in this case the main body of the satellite), and a Passive Unit (PU) attached to the target to be monitored (i.e. the reflector). The main purpose of ATOM is to relate the reference system of the antenna to the reference system of the satellite such that it is possible to know the yaw, pitch and roll angles assumed by the reflector. The purpose of this study is to create an ATOM prototype and to evaluate its effectiveness in terms of maximum detectable angles. For simplicity’s sake, two different models were created, the first for evaluating yaw and pitch angles and the second for evaluating roll angle. The tests carried out show that it was possible to detect a maximum angular variation in pitch and yaw of the target equal to ±0.116°, while there is no limitation on the roll angle, thus meeting the expectations set by INRiM and requested by ESA.