This timelapse video shows the Total and Spectral Solar Irradiance Sensor (TSIS-1) experiment being removed from the SpaceX's Dragon CRS-13 trunk. It flew up as external cargo in the Dragon on a Falcon 9 rocket launch on December 15th 2017. The TSIS-1 was then installed on the International Space Station's ExPRESS logistics carrier (ELC)-3.
TSIS-1 makes measurements of total and spectral solar irradiance (TSI and SSI, respectively). TSI is required for establishing Earth’s total energy input while SSI is needed to understand how the atmosphere responds to changes in the sun’s output. Solar irradiance is one of the longest and most fundamental of all climate data records derived from space-based observations.