The Medium Resolution Imaging Spectrometer (MERIS) was a programmable spectrometer on the Envisat mission, operating in the solar reflective spectral range. Although primarily dedicated to ocean colour observations, MERIS broadened its scope of objectives to atmospheric and land surface related studies. MERIS had a high spectral and radiometric resolution and a dual spatial resolution, within a global mission covering open ocean and coastal zone waters and a regional mission covering land surfaces.
One of the most outstanding features of MERIS was the programmability of its spectral bands in their width and position. MERIS was developed under the leadership of ALCATEL Space Industries. MERIS was operational throughout the Envisat mission lifetime, from 2002 to 2012, and the first data from the instrument was available from May 2002.