The Sun is the predominant source of energy input to Earth. Solar radiation ensures the maintenance of the appropriate range of temperatures for the sustenance of life on Earth, by driving land surface heating, plant productivity, and oceanic and atmospheric circulations. Because of the Sun’s dominant influence on Earth’s function, it is important to accurately measure the solar input to Earth or solar irradiance. Measurement of the total solar irradiance (TSI) is essential for quantifying Earth’s energy budget.

NASA's Total and Spectral Solar Irradiance Sensor, or TSIS-1, is a mission to measure the Sun's energy input to Earth. Various satellites have captured a continuous record of this solar energy input since 1978. TSIS-1 sensors advance previous measurements, enabling scientists to study the Sun’s natural influence on Earth’s ozone layer, atmospheric circulation, clouds and ecosystems. These observations are essential for a scientific understanding of the effects of solar variability on the Earth system. TSIS-1 launched Dec. 15, 2017, the International Space Station on a SpaceX Falcon 9.