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

A number of different 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 Solar Constant (SOLCON) experiment and the Solar Variability-1 (SOVA 1) experiment, as well as the SOVA 2 and Active Cavity Radiometer (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.