The Envisat geophysical validation programme

Envisat is ESA´s advanced Earth observing satellite designed to provide measurements of the atmosphere, ocean, land and ice over a five year period. As the successor to the highly successful ERS-1 and ERS-2 satellites it will provide direct continuity of measurement with most ERS instruments. The payload includes three new atmospheric sounding instruments designed primarily for atmospheric chemistry, including measurement of ozone in the stratosphere. There is an advanced SAR which can collect high resolution images with a variable viewing geometry, together with new wide swath and selectable dual-polarisation capabilities. A new imaging spectrometer is included for ocean colour and vegetation monitoring, and there are improved versions of the ERS radar altimeter, microwave radiometer and visible/near infra-red radiometers, together with a new very precise orbit measurement system. An essential preparation of the Envisat data exploitation is the validation of the geophysical data products which, according to the international CEOS standard is defined as the assessment by independent means of the quality of the data products derived from the system output. The geophysical validation programme is a collaborative effort coordinated by the ESA and consists of a number of validation activities proposed under the Announcement of Opportunity for Envisat data exploitation (AO) and of additional activities by investigators under contract. In a number of instrument and discipline-specific working groups correlative observations are planned to compare Envisat measurements with independent measurements