A close-up view of TSIS-1 as deployed on the International Space Station ExPRESS logistics carrier (ELC)-3. The TSIS-1 Thermal Pointing System (TPS) is deployed above the ELC after installation in order to provide sufficient clearance to track the sun each orbit with a two-axis gimbal. Courtesy NASA/LASP

In terms of climate change research, scientists need to understand the balance between energy coming in from the Sun and energy radiating out from Earth, as modulated by Earth’s surface and atmosphere. That’s why NASA launched the TSIS, the Total and Spectral Solar Irradiance Sensor.

The TSIS acquire measurements of total and spectral solar irradiance (TSI and SSI, respectively). It is used to establish Earth’s total energy input and how the atmosphere responds to changes in the sun’s output.