The Envisat (Environmental Satellite) satellite is an Earth-observing satellite built by the European Space Agency. It was launched on March 1, 2002 aboard an Ariane 5 into a Sun synchronous polar orbit at a height of 790 km (+/- 10 km). It orbits the Earth in about 101 minutes with a repeat cycle of 35 days.

Envisat carries an array of 9 Earth-observation instruments that gather information about the earth (land, water, ice, and atmosphere) using a variety of measurement principles.

Several of the instruments are advanced versions of instruments that were flown on the earlier ERS-1 and ERS-2 missions and other satellites.

• ASAR (Advanced Synthetic Aperture Radar) can detect changes in surface heights with sub-millimeter precision.
• MERIS (MEdium Resolution Imaging Spectrometer) produces 2-dimensional images using a 15-band spectrometer
• AATSR (Advanced Along Track Scanning Radiometer) can measure the temperature of the sea surface
• RA-2 (Radar Altimeter 2) is a dual frequency Nadir pointing Radar operating in the S band and Ku bands, it is used for measuring ocean topography, map/monitor sea ice and measure land heights.
• MWR (Microwave Radiometer) for measuring water vapour in the atmosphere and give corrections for the Altimeter
• DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) for orbit determination to within 10 cm or less
• GOMOS (Global Ozone Monitoring by Occultation of Stars) looks to stars as they descend through the Earth's atmosphere and change color, which also tells a lot about the presence of gases such as O₃ (ozone), and allows for the first time a space-based measurement of the vertical distribution of these trace gases.
• MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is a spectrometer
• SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY) compares light coming from the sun to light reflected by the Earth, which provides information on the atmosphere through which the earth-reflected light has passed.

External links

• Envisat-homepage at ESA http://envisat.esa.int/