Concept Development for the Thermal Management of the Russian American Observational Satellites (RAMOS)

University of Utah

For the past several years, cryogenically cooled sensors have become an increasingly popular method of observation and study for both space-based and ground-based operations. Accordingly, various cooling techniques have been developed to accommodate this group of sensors. Because of rising performance standards and escalating cost limitations, cryocoolers have become an impressive cooling technique to consider. This report focuses on the use of a mechanical cryocooler in conjunction with the Russian American Observational Satellites (RAMOS), a future pair of earth-imaging satellites which will fly infrared radiometers.

The RAMOS program consists of mapping the earth's surface in stereo using two co-orbital satellites. The American Observational Satellite (AOS) will utilize an infrared radiometer with the telescope focal plane assembly (FPA) operating at approximately 60 K. The FPA will be cooled using a multiple cryocooler configuration. The use of multiple coolers introduces redundancy into the cooling system-a redundancy which has been absent from many previously flown satellites. In addition, the cooling system will incorporate various other new technologies, such as thermal disconnects, a thermal storage unit, low-resistance flexible thermal links, etc., to meet the overall system objectives and requirements. Thermal storage units are discussed as a means of eliminating cryocooler self-induced vibration and passively controlling FP A temperatures. Incorporating thermal switches and thermal storage units into a cooling system design can alleviate the concerns of cryocooler vibration and parasitic heat loads. An understanding of these concepts and configurations will assist in the design of similar optical instruments for both space-based and ground-based exploration campaigns.