Application of Cryogenic Electrical Substitution Radiometers in the Calibration of Solar-Terrestrial Remote Sensing Instruments

Abstract

We describe two recent applications of cryogenic Electrical Substitution Radiometers (ESRs), which can provide significantly improved accuracy and sensitivity in the calibration of solar-terrestrial remote sensing instruments. In the first, a portable UV filter radiometer was calibrated at 257 nm using a cryogenic ESR and an intensity-stabilized laser. This filter radiometer was then used to measure the UV irradiance at 257 nm of deuterium lamps and of the SURF II synchrotron. Our results indicate that the accuracy of these measurements is three to eight times better than presently achieved with calibrations of these source standards, at this wavelength. Improvement of UV calibrations is critical to the success of NASA remote sensing of ozone, and of related solar UV irradiance variations. In the second application, a fast cryogenic ESR was developed for use at TRW as a spectrally flat transfer standard, to provide radiometric calibrations of the CERES spectroradiometer with accuracies of better than 1% in the short-wave band and 0,5% in the long-wave and total bands. The CERES instrument is designed to provide improved measurements of the Earth's radiation budget for climate studies.