RendezVous Sensor for automatic guidance of transfer vehicles to ISS concept of the operational modes depending on actual optical and geometrical-dynamical conditions

Based on an ATV RendezVous Predevelopment Program initiated by ESTEC, an automatically operating Rendez Vous Sensor (RVS) has been developed. The sensor - a Scanning Tele-Goniometer - shall guide docking and retreat of the European Automatic Transfer Vehicle (ATV) as well as berthing and retreat of the Japanese H-II Transfer Vehicle (HTV). The sensor performance will be strongly connected with the properties of cooperative targets, consisting of an arrangement of retro reflectors mounted on ISS each. The RVS software is not limited to measurement data evaluation tasks but also serves for sensor health supervision, sensor communication with GNC and - in particular - for automatic target acquisition and tracking. The moding concept for automatic acquisition and tracking of the target shall be analysed in this publication. The RVS software moding has been tailored to the conditions resulting from the approach and retreat characteristics of the chasers, considering the physical properties and constraints of sensor and target. Different specifications of the optical and geometrical-dynamical conditions for ARP-RVS, ATV-RVS and HTV-RVS shall be considered, as well as the experiences gathered during two flight missions of the ARP-RVS on Shuttle Atlantis to the MIR Station, for the definition of the sensor operational modes, mode transitions, and scan window sizes. The resulting moding approaches shall be discussed, similarities and differences of software moding definitions for the three sensors shall be identified and justified.