A CRYOGENIC ABSOLUTE RADIOMETER FOR EARTH RADIATION SENSING

THE PURPOSE OF OUR RESEARCH PROGRAM IS TO DEVELOP A HELIUM-COOLED ABSOLUTE RADIOMETER SUITABLE FOR WIDE-BAND MEASUREMENTS OF THE EARTH'S RADIATION AT AN ANGULAR RESOLUTION TWO ORDERS OF MAGNITUDE BETTER THAN ACHIEVED WITHTHE EXISTING ERBE RADIOMETERS. WE HAVE CONSTRUCTED AND CHARACTERIZED A HELIUM-COOLED RADIOMETER OVER THE PAST FOUR YEARS. THIS SUCCESSFUL INSTRUMENT IS OPTIMIZED FOR LABORATORY STANDARDS APPLICATIONS AND IS PRESENTLY BEING USED FOR STUDIES OF PHOTODIODE YIELD UNDER LASER ILLUMINATION. THE AIM OF THIS PHASE I STUDY IS TO DESIGN AND CONSTRUCT AN ULTRA LOW-MASS RECEIVER FOR THIS RADIOMETER AND TEST ITS PERFORMANCE AGAINST A NUMERCIAL HEAT FLOW MODEL. THIS COMPARISON WILL ENABLE US TO DETERMINE WHETHER THE DRAMATIC ADVANTAGES IN SENSITIVITY ANDTIME CONSTANT THAT A HELIUM-COOLED RADIOMETER SEEMS TO OFFERIN SUCH A MEASUREMENT CAN BE REALIZED IN PRACTICE. IF THE PHASE I RESULTS ARE FABORABLE, WE WILL REQUEST PHASE II SUPPORT TO CONSTRUCT A PROTOTYPE HELIUM-COOLED RADIOMETER OPTIMIZED FOR EARTH RADIATION MEASUREMENTS FROM THE SHUTTLE AND THE SPACE STATION.