Traceable Radiometry Underpinning Terrestrial and Helio Studies

The Traceable Radiometry Underpinning Terrestrial- and Helio-Studies mission (TRUTHS) is a planned European Space Agency (ESA) satellite.

[3] Alongside communications and navigation equipment, the scientific payload of the satellite would include three instruments: the cryogenic solar absolute radiometer (CSAR), the onboard calibration system (OBCS), and the hyperspectral imaging spectrometer (HIS).

[3] The cryogenic radiometer is the primary standard used by national metrology institutes for radiometric measurements and "recommended as the means to achieve SI traceability".

The mission is led by the UK National Physical Laboratory (NPL) and its lead scientist for EO, Nigel Fox.

[4] In order to obtain both scientific and financial support for the mission, many reports and academic publications were produced by Fox and collaborators over several decades.