Total solar irradiance has been measured from space since 1978, providing the best data record of the net radiative inputs driving the Earth’s climate system. Offsets and drifts due to calibration differences between the instruments contributing to this record have made estimating the time-dependent uncertainties associated with solar irradiance composites difficult, particularly for external data users; yet such composites and uncertainties are required for accurately assessing solar influences on Earth’s climate.

With modern improvements in ground calibration capabilities, recent tests of instruments representing those acquiring measurements over the last four decades, the launch of new solar irradiance instruments benefitting from those modern calibrations, and the current availability of investigators responsible for the historical and the newer flight instruments, now is an opportune time to assess this important record’s accuracies. ISSI provides a good forum and location to focus the international members representing the current and prior irradiance instruments with the intent of

1. Assessing instrumental accuracies and uncertainties, and
2. Producing and publishing an irradiance composite record having time-dependent uncertainties based on discoveries from recent tests.