Washington
—
Standing 10-meters and weighing 8,200-kilograms at launch, the European Space Agency
(ESA) says its
Envisat satellite is by far the largest European Earth observation spacecraft ever built. And it will be the last of ESA’s behemoth Earth watchers.
An Ariane 5 rocket launched Envisat March 1, 2002, from Kourou, French Guiana, into sun-synchronous polar orbit at an altitude of 800 kilometers.
Envisat, which stands for environmental satellite, was designed to succeed
the space agency’s ERS-1 and ERS-2 satellites. But with ERS-2’s extended operational life, Envisat sometimes works in concert with ERS-2.
Envisat
acts as an Earth-science observatory, monitoring the land, atmosphere, oceans and icecaps, and
tracks environmental and climatic changes.
“This satellite was conceived when we had all kinds of programs scheduled for in-orbit servicing as part of the international space station,” an ESA official
said in a February 1996 Space News article.
Though conceived in the 1980s, d
evelopment of Envisat began
in 1990, the ESA Web site said. The satellite was designed by
ESA’sNoordwijk, Netherlands-based Estec, the agency’s
scientific and technical center.
Matra Marconi Space, the French-British company that
merged with Daimler Chrysler Aerospace’s
space sector
to form
Astrium in May 2000,
was prime contractor on the project.
In addition to
its current climate-monitoring functions, the satellite also was
designed to carry out meteorological operations. Envisat was originally called the
Polar Observation Earth Mission, or POEM-1,
but the meteorological mission was shunted into the Metop-1 satellite in mid-1993, the ESA Web site said.
Still,
with 10 optical and radar instruments, Envisat
was a large platform at a time when the industry trended toward
smaller, more specialized spacecraft –
earning
the satellite a fair amount of criticism during its development.
“Now everything has been cut back and transformed, except Envisat,” the ESA official said in
February 1996.
“Envisat is what you get when you say ‘yes’ to experimenters and equipment suppliers everywhere,” a French space agency CNES official, who did not want to be identified, said in an Oct. 1995 Space News article.
Today, Envisat sends science data through ESA’s Artemis relay satellite at a rate of more than 280 gigabytes a day, according to the ESA Web site
. The relay system enables Envisat’s instruments to continuously gather science data.
The
data collected by Envisat has been used to better model climate change. “The global sea temperature has been changing over the years. In fact, it has been changing ever since records began but there is now evidence there is a distinctive upward trend in global sea temperature, and this we can now see from measurements made from Envisat,” David Llewellyn-Jones, a professor with the Earth Observation Science Group at the University of Leicester in Britain, said in a February 2006 article on the Physorg.com Web site.
The satellite also helped
determine that the Greenland glaciers are melting at twice the rate than previously
thought, the Physorg.com article said.
Envisat
instruments have been utilized in approximately 1,400 different scientific projects, according to a presentation in late November at the Fringe 2007 Workshop in Frascati, Italy.
Scheduled to retire in 2010, Envisat will not get a one-for-one
replacement. ESA made the decision to scale down its Earth-observing satellites. Sentinel-1,
a 2,280-kilogram
radar observation satellite, is
slated to launch in 2011, and
will perform only some of Envisat’s duties.
