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European Space Agency

Press Release

Envisat MERIS image of the world March 2003

19 June 2003
 
The global reach of the Medium Resolution Imaging Spectrometer
(MERIS) instrument on board ESA's Envisat environmental satellite is
revealed by this image of our planet Earth as it looked in March
2003. 
 
This is a mosaic made up of true colour images using three out of 15
MERIS spectral bands taken from Envisat in polar orbit at an altitude
of 800 km, with data combined from around 500 separate orbital
segments with the intention of minimising cloud cover as much as
possible. The image has a 1.2 km resolution and is made up of 40,000
by 20,000 pixels, equal to 2.5 gigabytes of output data.

MERIS records surface reflectivity, and a wide variety of land
surface coverings can be discerned in this way, from ice to forest,
grassland to desert. This being early spring, much of the Northern
hemisphere remains covered in snow and ice, with snows extending far
down across Russia. Comparatively small geographical features can be
clearly made out, such as the increasingly desiccated Aral Sea in the
lowlands of Central Asia, positioned east of the Caspian Sea.

In addition MERIS shows how the Earth's oceans vary in colour almost
as much as the land. Particularly noticeable is the effect of the
Gulf Stream around the British Isles with greenish sediment and
phytoplankton seeming to flare off the coast, the distinctive water
colour in the shallows of the Bahamas, and the coral reefs off
Australia. Artefacts of Envisat's orbital passes can also be detected
around the equatorial ocean areas of the image, caused by the sun
glinting off the sea surface.

GAEL Consultant, a firm based in Champs-sur-Marne, France, prepared
the image for ESA. It was shown for the first time this week at the
ESA stand at the 2003 Paris Air Show at Le Bourget.

The full-resolution image is available to be zoomed into for close-up
detail by going to ESA's Web Map Server at webmap.esa.int and
following the link at the bottom of the page. Just form a rectangle
with the cursor to select your area of interest.
 

Envisat MERIS Europe mosaic

The cloud-free face of Europe in the summertime is shown by this
mosaic of true-colour land images taken by the Medium Resolution
Imaging Spectrometer (MERIS) instrument on board ESA's Envisat
environmental satellite.

The image is a composite of 85 reduced and full resolution images
acquired by MERIS in the summer of 2002, using three out of 15 MERIS
spectral bands, taken from Envisat in polar orbit at an altitude of
800 km. By representing the arithmetic average reflectivity, it
displays the range of vegetation cover across Europe and North
Africa's land surface - including the striking green triangle of the
Nile Delta, surrounded by arid desert.

Young graduate Ana Silia Calzada, a member of the ESA training
programme New Opportunities for Women, prepared this test of Level 3
product from raw Level 1 top-of-atmosphere data using the Envisat (A)
ATSR and MERIS toolbox software algorithms available to ESA Principal
Investigators (PIs).

"This image is really a demonstration of what can be done with the
software tools that ESA provides," explained Silió. "I basically put
myself in the situation of the user to show how scientifically useful
multi-temporal data can be generated. I think of it as a work in
progress, since more detail can always be added."

The angle of the mosaic is due to the path of Envisat's polar orbit
in relation to the Earth. This image was shown for the first time
this week at the ESA stand at the 2003 Paris Air Show at Le Bourget.

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