Successful launching of the booster Ariane 5.

The satellite travels in polar orbit, 800 kms above the surface of the Earth. Envisat weighed 8200 kg when launched. This comprises 300 kg engine fuel which is necessary in order to secure that antennas and instruments are adjusted correctly when it travels in orbit. In addition the instruments weigh 2100 kg.

The 70 m² solar panel has been constructed to produce 6600 W electricity.
For continuous operation the instruments need access to 1700W. The satellite is designed to circle in orbit for a period of 5 years.

The satellite will among other things survey shipping traffic, fishing, the ice conditions of arctic areas, oil fields, algae, ocean currents and the height of waves. In addition, the instruments on board the satellite will give information about greenhouse gases and the dynamics of the atmosphere.

Envisat will give the member countries of ESA a better possibility for observations of the atmosphere, oceans, shore and ice during a 5 year period.

The observations will provide further knowledge about the Earth, and also possibilities for surveillance of the environment and climatic changes.

The illustration shows an example of the application of data from the Envisat (ESA).

The following is taken from ESA's Envisat programme:
- to secure continuity of the observations that started with the satellites ERS-1 and ERS-2, especially the radar based observations
- try to improve these observations, especially ocean and ice observations
- increase the number of observation parameters, in order to increase in this way knowledge of the factors that are decisive for the environment.
- to give a considerable contribution to environmental research, especially within the chemistry of the atmosphere, ocean studies (including marine biology) and the physics of the solid Earth
- to search for more effective surveillance and control of the resources of the Earth, both renewable and non-renewable

The Envisat programme consists of four main elements: the ground segment (two control stations), the booster (Ariane 5), the space segment (the satellite itself), and the relay satellite system named Artemis.

Read more on ESA's web site, http://envisat.esa.int/

GOMOS: Global Ozone Monitoring by Occultation of Stars.

Illustration of the instruments on board the Envisat (ESA).

GOSMOS is a new Ozone instrument. The measurements are based on studying the spectrum of the stars outside and through the atmosphere of the Earth.

As a result, it is possible to build up vertical profiles of water and ozone through the atmosphere at altitudes between 20-100 kms. The collection of data is so enormous that the data being produced equals 360 separate ground stations.

MIPAS: Michelson Interferometer for Passive Atmospheric Sounding
Mipas observes the atmosphere in the average infrared field of the spectrum. MIPAS measures atmospheric pressure, temperature, spreading of aerosol, tropospheric cirrus clouds and stratospheric ice clouds and also the concentration of tracer gases. MIPAS may carry out parallel measurements of more than 20 tracer gases.

The data from MIPAS make it easier to understand the ozone problems and climatic warming. Measurements from MIPAS provide data with a unique global coverage, independent of seasons and light conditions. The MIPAS instrument may also observe vertically in relation to the path of orbit.

SCIAMACHY: Scanning Imaging Absorption SpectroMeter for Amospheric Chartography.
SCIAMACHY measures atmospheric tracer gases and concentrations of aerosol by observing solar light that is reflected and spread (a very wide range of wavelengths).

SCIAMACHY gives the total quantity of gases and profiles of the atmosphere. SCIAMACHY is an all-round instrument that enables investigations of the effects of forest fires, dust clouds, industrial pollution and volcanic activity.

AATSR: AdvancedAlong-Track Radiometer
AATSR scans the surface of the sea at several infrared and visible frequencies in order to give an accurate registration of the temperature on the surface of the sea. The instrument registers the surface of the sea from two angles, thus practically removing the effect of atmospheric disturbances and gives an accuracy of 0.3oC.
Registrations from AATSR may discover warm spots from forest fires. AATSR may be suitable for surveying the extensiveness of vegetation in different regions.

ASAR: The advanced Synthetic Aperture Radar
The ASAR instrument is a good aid in studying ocean phenomena. Active radar produces images that are equally clear day and night and it may also penetrate the cloud cover.

The ASAR images give information about fronts and whirls on the surface currents. The radar images from ASAR may also be used for deciding size, position and the speed of ships and in this way become part of the security service at sea.
The ASAR images will secure information about ice conditions in the Arctic and Antarctic.
The ice surveillance services in the Nordic countries intend to use data from Envisat. ASAR is also an important instrument of observation on shore. The most important tasks are surveillance of forest, Earth humidity and changes in the landscape. ASAR data are also to be used in geological exploitation and mapping.

MERIS: Medium Resolution Imaging Spectrometer
MERIS takes pictures of the surface and the clouds in solar light catching visible light and some of the infrared part of the spectrum. The instrument is able to decide the exact "colour" of the ocean and the coastal areas.

These observations tell something about biological activity and other processes, surveillance of clouds, discovery of invisible water vapour in the atmosphere, and identification of plants at different levels of growth. Information from MERIS about the "colour" of the water makes it possible to measure the concentration of algae of large areas.
MERIS is also a tool for studying and supervising the flourishing of algae along the coast. Data from MERIS will also be used in the evaluation and surveillance of water quality along the coast.

RA-2: Radar Altimeter
RA-2 measures the altitude of the satellites above the surface of the sea with a precision of 4.5 cm. Combined with exact data of orbital motion from DORIS, RA-2 measurements will give a profile of the ocean or the ice surface below. RA-2 gives weekly measurements of the level of the surface of the sea, the heights of waves and wind speed. In addition, altitude of the terrain and the level of lakes.

RA-2 carries out measurements of deviations from an even surface of the sea. All oceanic currents create gradients on the surface. Measurements of these gradients may reveal characteristics, positions and strength of the oceanic currents. Above shore the RA-2 instrument will be used among other things for providing better survey of topography and geological structure.

MWR: Microwave Radiometer
The data from the microwave radiometer MWR are useful for deciding surface radiation on the ground and for measuring the total amount of water vapour and water contents of the clouds. This is used in order to adjust RA-2 radar signals.

DORIS: Doppler Orbitography and Radiopositioning Integrated by Satellite
Doris is a system that may decide the precise position of the satellite. This may be done with a precision of 4.5 cm. Path speed may be decided with a precision of 0.4 mm/s. This is done by the instrument receiving signals from a close network of stations on the ground.

The system gives a possibility not only of being able to determine the satellite orbit, but also of providing data that may ease the understanding of the dynamics of the Earth's crust, supervise glaciers, landslides and volcanoes. DORIS may also secure better models of the gravitation field of the Earth and of the ionosphere.

LRR: Laser Retro-reflector

The LRR instrument on board the ERS-1 satellite. This satellite is similar to the one on board the Envisat.

A laser retroreflector is mounted on a pillar attached to the nadir panel close to the RA-2 antenna. It has two functions: support-to-satellite ranging; and RA-2 altitude calibration.
The LRR is a passive device which is used as a reflector by ground-based SLR stations using high-power pulsed lasers.

For more information, visit Envisat site.