MERIS is a passive imaging sensor flying on Envisat which was launched in 2002. Similar to other sensors such as MODIS and AVHRR, it is designed to image the earth at a global and regional scale. The primary mission of MERIS is to monitor oceans and coastal areas, but has many land applications as well. Its land mission is to study the role of terrestrial surfaces in climate dynamics and biogeochemical cycles for climate change.
MERIS has 15 spectral bands within the visible and near infrared range, each capable of gathering data at a resolution of 260m across track x 300m along track. The narrow bands of MERIS make it possible to derive more accurate land cover and vegetation indices than other systems such as AVHRR.
The standard products available through MERIS include: radiance, reflectance, and two vegetation indices known as the MERIS Global Vegetation Index (MGVI) and the MERIS Terrestrial Chlorophyll Index (MTCI). Products at a reduced resolution (1040m x 1160m) can usually be obtained free of charge over the internet, while full resolution products (260m x 300m) usually have to be requested and carry a fee.