Abstract: A spaceborne radiant cooler for cooling multielement infrared detector array in Infrared Multispectra Scanning System （IRMSS） is developed. The infrared remote sensors used in space must be cooled to the low temperature and The radiant coolers are quite suitable to the needs of such an application. The developing process, program design, its fundamental construction, theoretical calculating method, environment simulation experiments and their results are described. The working properties in orbit are also included.