The goal of this proposal is the improvement of the solar UV irradiance dataset as originally measured by the NASA-supported SUSIM UARS experiment

The solar ultraviolet spectral irradiance monitor (SUSIM) aboard the upper atmosphere research satellite (UARS) gathered solar UV irradiances on nearly a daily basis for nearly 14 years (1991-2005). As has been typical of NASA experiments operating on extended missions the SUSIM program funding was ended abruptly providing for only marginal postmission data processing. Accordingly although the resulting SUSIM dataset has proved to be a valuable addition to the overall set of solar irradiance measurements gathered over the past 3 decades the SUSIM observations can be substantially improved via a modest effort. The SUSIM data consists of absolutely calibrated UV solar spectral irradiances and integrated UV irradiances for wavelengths 115-410 NM at 1.1 NM resolution. These data were calibrated through sophisticated and complex algorithms based on coincident solar and onboard lamp measurements by redundant optical channels. More specific scientific data improvements provided through this proposal include: 1) reduction in the noise in the solar UV irradiance time series 2) removal of artifacts that represent uncorrectable errors or problems in the underlying measurement data 3) recalculation of calibration data where these had been adversely affected by data errors and artifacts and improved metadata which for example describes how the irradiances are calculated. The data products resulting from this work will be a new version ("23") of the solar UV integrated and spectral irradiances reprocessed with an updated calibration. These data comprise 1) level 3 irradiances integrated into 1 NM bins level 2 spectral irradiances presented on (VARYING) instrumental wavelengths 3) integrated irradiances onto irregular 5-10 NM regions optimized for noise reduction and 4) solar indices e.g. LY-a line irradiance and a mgii index. These data products will have more specific and accurate error estimates specifically associated with them. Documentation will include (for the first time) a detailed description of how the data were processed from the raw telemetry to final product. Each of the irradiance data products will be made available in several forms thus providing users with data access options. Specifically the irradiance data will be provided in the forms of CDF netcdf and ascii files. Documentation will be embedded into the data when practical and we will aggressively take advantage of self documentation features and opportunities. These files will be submitted to the sdac for general data access and archival storage. We also will work with hdmc and NASA HQ as well to develop an acceptable SUSIM data plan. The SUSIM data has seen wide usage both in the US and abroad and continues to do so today. Notably IT overlaps with similar data from the sorce mission providing a basis for intercomparisons and validation. Currently NASA sponsors an effort to calibrate solar UV irradiances from the NOAA-16 and -17 satellite SBUV2 instruments both of which gathered UV irradiance data for 10+ years. The PI of this proposal participates in the current solar irradiance science team (SIST) that has met in 2016 and 2017. The SUSIM calibration data is playing an important role in this effort especially in intercomparisons among the sorce NOAA and SUSIM instruments. This proposed work provides important support of NASA'a heliophysics science goals. Among these is to understand the sun and its variability. IT also supports our understanding of the impact of solar activity on the earth and solar system. Third IT enables research on the connections among the sun earth and solar system supporting both our scientific knowledge and human exploration. The improved and more accessible solar UV irradiance record resulting from this work supports these listed goals.