The Committee on Earth Observation Satellites (CEOS) has recently established RadCalNet, a network of primarily desert-like sites which are equipped with autonomous instrumentation to allow top of the atmosphere reflectance values to be determined every 30 minutes. These are provided on an open access web portal to any satellite operator so they can check the consistency of their satellite's measurements.
NPL has played a central role in the development of RadCalNet, with responsibility for developing the guidelines on how to establish traceability and uncertainty for all the member sites. In addition, it has established and operates one of the member sites, Gobabeb in Namibia, on behalf of the European Space Agency.
RadCalNet not only supports the major space agencies, but is also providing a valuable resource for new commercial satellite operators and, in particular, constellations of microsats which are too small to have any on-board calibration capabilities.