PTB’s contribution to the mission was funded by ESA’s General Support Technology Programme (GSTP), the agency’s initiative enabling the development of new technologies.

“The spectrometer onboard the FORUM mission will measure Earth’s outgoing radiation with very low uncertainty, meaning its measurements will be very accurate,” explains Christian Monte, head of the Detector Radiometry and Radiation Thermometry department at PTB. “A level of uncertainty this low was at the limit of what was achieved in the best labs, on ground, five years ago. Never in space.”

To operate, the FORUM spectrometer needs a reference source, a device that will be used to calibrate the instrument to make sure its measurements remain as accurate as possible while in space. For a spectrometer of this kind, this reference source is a ‘blackbody’ – a physical object that, in theory, absorbs all electromagnetic radiation and reflects none.