Literally, satellites are celestial objects, natural or artificial, which are periodically moved under the effect of gravity exerted by a body of greater importance. Used for over 50 years, satellites are launched into space in the framework of specific missions that fulfill a wide variety of objectives:
- weather forecasting and climate change studies;
- understanding of how the Earth system works and protecting the environment;
- solar system exploration and knowledge acquisition in astronomy;
- telecommunication for television and / or telephony;
- navigational aids and traffic control;
- surveillance of military operations.
Depending on the mission associated with it, the satellite may include a set of measuring instruments to take pictures, record data, etc. Several satellites have the mission to observe and acquire information on the Earth system and more particularly on the oceans. The parameters observed are varied and range from global observation of the marine geoid to surface measurements, as well as observation of the color of the oceans and sea states. Still in progress, completed, or to come, a whole ensemble of satellite missions allows global observation of the oceans.