Cryogenic qualification testing of dichroic filters 1-5 for ESA’s ARIEL mission

ARIEL, the Atmospheric Remote‐sensing Infrared Exoplanet Large‐survey mission, is ESA’s Cosmic Vision M4 mission and will study the atmospheres of up to 1000 exoplanets. It uses a set of five dichroic filters (D1 to D5) to split the incoming bandwidth of 0.5 to 7.8 μm and will operate between 40 K and 60 K. We will present ongoing efforts of qualification testing of the D1 - D5 dichroics. Our Tests are performed at ambient and cryogenic temperatures and include transmission and reflectivity spectra, the cryogenic shift of the dichroic’s transition wavelength, wave-front error measurements, humidity testing and cryogenic cycling between 37 K and 323 K. We will give a progress report and will elaborate on achieved results, experimental setups and encountered challenges. We will also discuss steps to establish an instrumentation clean room, suitable for flight acceptance testing for in-space instrumentation.