Hardware-in-the-Loop Simulations with Umbra Conditions for Spacecraft Rendezvous with PMD Visual Sensors

This paper addresses the validation of a robust vision-based pose estimation technique using a Photonic Mixer Device (PMD) sensor as a single visual sensor in the close-range phase of spacecraft rendezvous. First, it was necessary to integrate the developed hybrid navigation technique for the PMD sensor into the hardware-in-the-loop (HIL) rendezvous system developed by the German Aerospace Center (DLR). Thereafter, HIL tests were conducted using the European Proximity Operation Simulator (EPOS) with sun simulation and in total darkness. For the future missions with an active sensor, e.g., a PMD camera, it could be useful to use only its own illumination during the rendezvous phase in penumbra or umbra, instead of additional flash light. In some tests, the rotational rate of the target object was also tuned. Unlike the rendezvous tests in other works, here we present for the first time closed-loop approaches with only depth and amplitude images of a PMD sensor. For the rendezvous tests in the EPOS laboratory, the Argos3D camera was used at the range of 8 to 5.5 m; the performance showed promising results.