Development of the re-entry spectrometer RESPECT for the ESA capsule EXPERT

Abstract

At IRS the RESPECT sensor system for in-flight emission spectroscopic measurements of re-entry body post-shock regimes is currently under development. Design solutions for this sensor system based on the basic conditions of ESA's EXPERT program are presented. The sensor head design is described with emphasis on the optical access to the plasma in the stagnation area. To justify the presented design the thermal and mechanical tests already performed are described. The present tests include thermal tests of the TPS window assembly and transmittance investigations of the sapphire window at high temperatures using plasma wind tunnel facilities at DLR and IRS. Both test campaigns have been concluded successfully, showing that the window assembly is withstanding the thermal loads of the EXPERT re-entry and that no substantial changes in the sapphire transmittance properties could be detected up to temperatures of 700 ∘ C . Mechanical testing has been limited so far to the spectrometer unit and has been performed using shaker facilities. The tests demonstrate that the chosen OceanOptics S2000 spectrometer can withstand the EXPERT-Volna vibrational launch environment and the EXPERT ballistic re-entry. In addition, the functionality of the sensor system in the harsh environment imposed by plasma wind tunnel tests has been approved. Summarizing all the tests performed to support the development of the sensor system it can be concluded that the presented sensor design can be fully applied for atmospheric (re-)entry mission such as EXPERT.