SOLAR-STELLAR IRRADIANCE COMPARISON EXPERIMENT-1 .2. INSTRUMENT CALIBRATIONS

The science objective for the Solar-Stellar Irradiance Comparison Expe riment (SOLSTICE) is to accurately measure the full disk solar spectra l irradiance in the ultraviolet (UV) spectral region over a long time period. The SOLSTICE design was driven by the requirement for long-ter m, precise solar photometry conducted from space. The SOLSTICE 1 is on the Upper Atmosphere Research Satellite (UARS), launched in September 1991 with the possibility for a 10-year operational mission. The in-f light calibration for SOLSTICE to meet its primary objective is the ro utine measurements of the UV radiation from a set of early-type stars, using the identical optical elements employed for the solar observati ons. The extensive preflight calibrations of the instrument have yield ed a precise characterization of the three SOLSTICE channels. Details of the preflight and in-flight SOLSTICE calibrations are discussed in this paper.