The Envisat satellite (envisat.esa.int), launched on 1 March 2002, carries ten instruments. Three of the instruments, MIPAS, GOMOS, SCIAMACHY, are aimed at atmospheric research and two multi-spectral imaging instruments, MERIS and AATSR perform land and marine observations. For geophysical validation, independent observations by a large number of in-situ, remote-sensing and satellite instruments, including those on space-borne platforms, will be used for comparison with the geophysical Envisat data products. For the five aforementioned instruments, the validation activities are performed by two dedicated teams which both use a storage and retrieval facility for correlative data. The validation activities have begun in April and will continue for the entire duration of the mission. In order to extract maximum information from the coincident measurements performed for validation, these correlative data are made accessible to all scientists and engineers performing the validation and calibration. For this purpose, a new data centre was commissioned by the European Space Agency (ESA) at the NADIR database (nadir.nilu.no/calval), hosted by the Norwegian Institute for Air Research (NILU).