The investigators are using an existing instrument, the Absolute Solar Transmission Interferometer (ASTI), to determine the exoatmospheric solar spectral radiance in the 1.0 to 5 micron region. The ASTI, originally developed to measure the solar spectral radiance at ground level for studying radiation budget, has a very large dynamic range, and a spectral resolution of 2 wave numbers. The measurements and their subsequent analysis determine the exoatmospheric solar radiance to a 2 - 3% uncertainty.
