SOLar-STellar Irradiance Comparison Experiment II (SOLSTICE II): End-of-Mission Validation of the SOLSTICE Technique

The SOLar-STellar Irradiance Comparison Experiment (SOLSTICE: McClintock, Rottman, and Woods, Solar Phys. 230, 225, 2005) onboard the SOlar Radiation and Climate Experiment (SORCE: Rottman, Solar Phys. 230, 7, 2005) observed ultraviolet solar spectral irradiance (SSI) from 2003 - 2020. This article gives an overview of the end-of-mission algorithms and calibration of SOLSTICE. Many of the algorithms were updated after the early mission, either due to an improved understanding of the instrument and the space environment, or due to operational constraints as the spacecraft systems aged. We validate the final official data version (V18) with comparisons to other observations and models. The SOLSTICE observations of the solar-cycle variability in the ultraviolet are compared to model estimates.