Envisat

Envisat ("Environmental Satellite") is a large Earth-observing satellite which has been inactive since 2012. It was launched on 1 March 2002 aboard an Ariane 5 from the Guyana Space Centre in Kourou, French Guiana, into a Sun synchronous polar orbit at an altitude of 790 ± 10 km.

Operated by the European Space Agency (ESA), it was the world's largest civilian Earth observation satellite. Its objective was to support the continuity of European Remote-Sensing Satellite missions, providing additional observations to improve environmental studies. To accomplish the global and regional objectives of the mission, numerous scientific disciplines used the data acquired from the sensors on the satellite to study atmospheric chemistry, ozone depletion, biological oceanography, ocean temperature and colour, wind waves, hydrology (humidity, floods), agriculture and arboriculture, natural hazards, digital elevation modelling (using interferometry), monitoring of maritime traffic, atmospheric dispersion modelling (pollution), cartography and snow and ice.

Envisat malfunctioned before it could be deorbited, and after losing contact with the satellite on 8 April 2012, ESA formally announced the end of Envisat's mission on 9 May 2012. The defunct satellite is considered space debris and orbits the Earth in about 101 minutes, with a repeat cycle of 35 days. An analysis that determined the 50 "statistically most concerning" debris objects in low Earth orbit ranked Envisat in 21st place.

Envisat was able to operate five years beyond its planned mission lifetime, delivering over a petabyte of data. At the time of its failure, Envisat had cost a total of 2.5 billion euro to develop, launch, and operate. The mission has been replaced by the Sentinel series of satellites. The first of these, Sentinel 1, has taken over the radar duties of Envisat since its launch in 2014.