ExoMars PANCAM High Resolution Camera (HRC): Evolution from BB to FM

Kurzfassung

This paper describes the development and testing of a focusing mechanism for the High Resolution Camera (HRC) of the ExoMars 2020 Rover. The mechanism will be used to re-position a lens barrel in order to refocus the camera. ExoMars 2020 is a cooperation between the European Space Agency and Roscosmos with a scientific contribution from NASA. The HRC is part of the PanCam (panoramic camera) which is composed of: -A Wide Angle Camera (WAC) pair, for multi-spectral stereoscopic panoramic imaging, using a miniaturised filter wheel (by TAS/RUAG/Space X and MSSL-UCL) -A High Resolution Camera (HRC) for high resolution colour image (by DLR Berlin & OHB) -PanCam Interface Unit (PIU) to provide a single electronic interface, and a PanCam Optical Bench (OB) for housing the PanCamand to provide planetary as well as dust protection (by MSSL-UCL). The HRC hardware is designed and produced by OHB System AG, Wessling and the DLR Institute for Planetary Research, Berlin. While the mechanism and the optics were developed by OHB, the focal plane and control board is under responsibility of DLR Berlin. One of the main challenges was to develop a mechanism capable of working within operational thermal environment of -55°C to +40°C (qualification level) and to survive a non-operational environment of -130°C to +50°C (qualification level). On top DHMR (dry heat microbial reduction) at +125°C had to be applied wherever possible. Cleanliness and planetary protection rules had highest priority with impact on selection of materials, lubrications, design, assembly, and testing which will be elaborated in the paper. The focus of the paper will be on the design and its evolution through the different stages from Bread Board to FM. Special attention is given to the improvements of the mechanism functionality after the breadboarding activities. In particular the QM design has been modified using a different lubrication concept (dry lubrication with gold) in order to cope with the large temperature range and high cleanliness requirements due to optics in close proximity. Additionally it will provide a detailed summary of the testing results from the BB and QM phases.