The Sentinel missions are developed for the operational needs of the Copernicus programme
Background
The Sentinel missions are developed specifically for the operational needs of the Copernicus programme.
Each Sentinel mission is based on a constellation of satellites to fulfil revisit and coverage requirements, providing robust datasets for Copernicus services.
Sentinel-1 is a polar-orbiting, all-weather, day-and-night radar imaging mission for land, ocean and emergency services.
Sentinel-2 is a polar-orbiting, multispectral high-resolution imaging mission for land monitoring, with imagery of vegetation, soil and water cover, inland waterways and coastal areas.
Sentinel-3 is a multi-instrument mission to measure sea-surface topography, sea- and land-surface temperature, ocean colour and land colour.
Sentinel-5 Precursor provides timely data on trace gases and aerosols affecting air quality and climate; Sentinel-4 delivers data from geostationary orbit and Sentinel-5 from polar orbit.
Sentinel-6 carries a radar altimeter to measure global sea-surface height, primarily for operational oceanography and for climate studies.
In plain words
Copernicus — The European Earth observation programme whose services the Sentinel satellites are built to supply.
Constellation — A group of satellites flown together so that a place on Earth is revisited more often.
Multispectral imaging — Imaging in several separate bands of wavelength at the same time.
Radar altimeter — An instrument that measures height by timing a radar pulse reflected from the surface.