ESA's Traceable Radiometry Underpinning Terrestrial- and Helio-Studies mission, or TRUTHS for short, will provide traceable International System of Units (SI) measurements of incoming solar radiation and of radiation reflected from Earth back out into space, with which to calibrate data from other satellites. In effect, this new satellite will provide the benchmark reference for radiation measurements to improve our understanding of climate change and help increase the precision of climate models. This will help to monitor the effectiveness of international policy to fight the climate crisis.