The objective of this activity is to develop and manufacture (at EM level) a Heat Switch to be be used in the 30-80K temperature range which is suitable for Operational Earth Observation missions. For such applications, both the thermal performances and reliability are critical parameters.

A number of upcoming or planned Earth Observation missions (e.g. Sentinel 3, MTG, Post-Metop, Premier etc.) require cryogenic cooling between 80 and 50K. To obtain this level of temperature, it is now common to use long life mechanical coolers (e.g. Stirling Coolers for Sentinel 3 and Pulse Tube cooler for MTG) which are most of the time redundant. Operational missions requiring to be Single Point Failure tolerant, the cryogenic system has to be sized taking into account a OFF redundant cooler. This introduces a large parasitic heat load in the order of the actual user load. The resulting system, with cryocoolers significantly oversized for the task, is not optimised.The addition of a reliable and thermally efficient Cryogenic Heat Switch in such system would permit to save >15% of Input Power or to reach lower detector temperatures with the same input power without adapting the technically challenging Cryocoolers.The main characteristics (TBC) of the Cryogenic Heat Switch shall be the following:? High Reliability.? Conductance >0.85W/K@50K? ON/OFF Ratio=1500After a design phase where all possible concepts shall be assessed and trade-offs performed, an Engineering model of the Cryogenic Heat Switch shall be manufactured and shall be submitted to a full comprehensive characterization and test program so as to demonstrate the full performance at a level of TRL 4.