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Envisat was launched
on 1st March 2002 by Ariane 5 and cost around €2bn. Its
planned mission length is 5 years and is designed to monitor
Earth’s land, oceans and atmosphere. Envisat carries
instruments to collect information that will improve understanding
of each part of the Earth system and to predict how changes
in one part will affect others. Many of Envisat’s instruments
are a development of those that flew on the European Space
Agency’s Earth-Observing missions of the 1990s (ERS-1
and -2). It will be possible, therefore, to make comparisons
between conditions observed during Envisat’s lifetime
and those recorded during the past 10 years.
Envisat’s orbit takes 101 minutes at an altitude of
800km. It is sun synchronous and has an angle of inclination
of 98 degrees. Although it has a 35 day repeat cycle, many
of Envisat’s instruments observe a wide swath of Earth
and so observe the whole planet every few days.
Applications of Envisat data include ice mapping, siting of
wind farms at sea, land use monitoring, potential forecasting
of ocean circulation and UV forecasting. Envisat ASAR products
are €300 with discounts for volume purchases.
Envisat's
instruments
| Instrument |
Main purpose |
| Global ozone
monitoring by occultation of stars (GOMOS) |
To observe the concentration
of ozone in the stratosphere. |
| Scanning Imaging Absorption Spectrometer
for Atmospheric Cartography (SCIAMACHY) |
To measure trace gases and aerosol concentrations
in the atmosphere. |
| Michelson interferometer
for passive atmospheric sounding (MIPAS) |
To collect information about chemical
and physical processes in the stratosphere, such as those
that will affect ozone concentration in future. |
| Medium resolution imaging
Spectrometer (MERIS) |
Measures radiation in 15 frequency bands
that give information about ocean biology, marine water
quality, vegetation on land, cloud and water vapour. |
| Advanced synthetic aperture
Radar (ASAR) |
All weather, day or night radar imaging. |
| Advanced along track scanning
radiometer (AATSR) |
To measure sea-surface temperature, a
key parameter in determining the existence and/or extent
of global warming. |
| Radar Altimeter (RA-2)
|
Measures distance from satellite to Earth.
So can measure sea-surface height, an important measurement
for monitoring El Nino, for example. |
| Microwave radiometer (MWR)
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Allows corrections to be made to radar
altimeter data. |
| Doppler Orbitography and
Radio positioning integrated by satellite (DORIS) |
Gives the position of Envisat in its
orbit to within a few centimetres. This is crucial to
understanding the measurements all the instruments make. |
| Laser retro-reflector (LRR) |
Reflects pulsed laser to ground stations
to help determine the satellite’s exact position
in its orbit. |
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