Development of a Compact and Cost Efficient Observational Strategy for the Long-term Measurements of Solar Spectral Irradiance

Accurate and continuous long-term measurements of solar spectral irradiance (SSI) are directly aligned with NASA Earth Science priorities to obtain data records to advance our understanding of the solar influence on Earth’s climate. A continuous SSI dataset is required to provide a climate quality record for validating climate model sensitivity to temporally and spectrally varying solar forcing and to quantify the wavelength dependent processes of climate variability. Recent advancements in spectral irradiance calibration facilities and techniques make it now possible to improve significantly the accuracy and traceability (<1% absolute uncertainty relative to SI standards) of future SSI observations and assure quantification of uncertainties as input to increasingly more sophisticated climate models. The Compact Spectral Irradiance Monitor (CSIM), developed under NASA ESTO IIP and ACT programs, represents a new approach to acquiring SSI measurements to meet future needs for compact, robust measurement systems at reduced overall costs. CSIM covers a continuous wavelength range of 200-2400 nm and meets the required SI-traceable accuracy and on-orbit stability for climate quality data records. We describe the development of a new 6U CubeSat integrated platform for obtaining high priority measurements of SSI and reduce the risk to the continuity of the long-term record. The complete effort takes advantage of new, emerging technologies in both instrument and small spacecraft developments demonstrating a cost efficient small satellite concept for long-term mission implementation. An emphasis on smaller platforms also potentially reduces access-to-space costs and delays through the use of smaller single launch vehicles or using excess capacity on larger launch vehicles. Ultimately, implementing this lower cost approach based on redundancy, with overlapping measurements, in a small satellite constellation can reduce the overall risk to the long-term SSI data record.