First realisation of the Space Absolute Radiometric Reference (SARR) during the ATLAS 2 flight period

Abstract A number of differnet solar constant observations all made from space during the ATLAS 2 mission have been gathered and compared to each other. The Sun did not have a single sunspot during several days. As eight of the radiometric channels were all within 0.1 %, the mean of the observations has been used to determine a set of adjustment factors providing de facto the definition of the Space Absolute Radiometric Reference (SARR). The differential absolute radiometers of SOLCON and SOVA 1, as well as the SOVA 2 and ACR radiometers that have been brought back to the Earth may, if used in the same conditions, reproduce and maintain the SARR for the future.