Overview of NASA’s Solar Irradiance Science Team #2 (SIST‐2) Program

The Solar Irradiance Science Team (SIST) #2 (SIST‐2) program is a competitively solicited National Aeronautics and Space Administration (NASA) Earth Science Division science research program providing 3‐year awards beginning in July 2018 to quantify and understand the solar irradiance variability and implications for Earth's climate and atmospheric composition. The purpose for the SIST‐2 program is limited to the accurate specification of the incoming solar irradiance into the Earth system considering the 44‐year satellite data record as well as proxies to which the satellite record can be tied. The SIST‐2 program funded eight research grants to study the variability of the total solar irradiance and solar spectral irradiance and to develop improved space‐based data sets, solar proxies, and variability models of the solar irradiance. The SIST‐2 projects are briefly introduced. Plain Language Summary NASA's Earth Science Division has a dedicated research program to understand the solar irradiance (brightness) and how much the solar radiation can vary over time scales of days to years to centuries. This program is called the Solar Irradiance Science Team (SIST), which started in 2015 with a set of 3‐year research grants, and then extended as the SIST‐2 program for 2018–2021. There are eight research grants to quantify and model the solar irradiance for the SIST‐2 program. Satellite observations of the solar radiation are analyzed to understand how much the solar radiation can vary, as well as how those results are combined with solar proxies to develop models of the solar variability for times and wavelengths when satellite observations are not available. Key Points The Solar Irradiance Science Team (SIST) #2 (SIST‐2) program is a research program from July 2018 to July 2021 for NASA’s Earth Science Division The SIST‐2 program has eight projects to study the variability of the total solar irradiance and solar spectral irradiance The SIST‐2 project teams develop improved space‐based data sets, solar proxies, and variability models of the solar irradiance