CRYOGENIC SOLAR ABSOLUTE RADIMETER CSAR

The Cryogenic Solar Absolute Radiometer (CSAR) is a new primary radiom etric standard for use in space traceable to the international. System of Units (SI) . CSAR will have the potential to measure the total irr adiance of the Sun with an uncertainty of 0.01% and a resolution of 0. 001%, more than a factor ten improvement over existing instruments. Si nce CSAR will be cooled by a mechanical cooler based upon the Stirling cycle its working lifetime is projected to be in excess Of 10 years.