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ESA declares end of mission for Envisat (Forwarded)

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Old May 9th 12, 04:51 PM posted to sci.space.news
Andrew Yee[_1_]
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Default ESA declares end of mission for Envisat (Forwarded)

European Space Agency
Paris, France

Press Release No. 15-2012 9 May 2012

ESA declares end of mission for Envisat

Just weeks after celebrating its tenth year in orbit, communication with the
Envisat satellite was suddenly lost on 8 April. Following rigorous attempts
to re-establish contact and the investigation of failure scenarios, the end
of the mission is being declared.

A team of engineers has spent the last month attempting to regain control of
Envisat, investigating possible reasons for the problem.

Despite continuous commands sent from a widespread network of ground
stations, there has been no reaction yet from the satellite.

As there were no signs of degradation before the loss of contact, the team
has been collecting other information to help understand the satellite's
condition. These include images from ground radar and the French Pleiades

With this information, the team has gradually elaborated possible failure
scenarios. One is the loss of the power regulator, blocking telemetry and

Another scenario is a short circuit, triggering a 'safe mode' -- a special
mode ensuring Envisat's survival. A second anomaly may have occurred during
the transition to safe mode, leaving the satellite in an intermediate and
unknown condition.

Although chances of recovering Envisat are extremely low, the investigation
team will continue attempts to re-establish contact while considering
failure scenarios for the next two months.

The outstanding performance of Envisat over the last decade led many to
believe that it would be active for years to come, at least until the launch
of the follow-on Sentinel missions.

However, Envisat had already operated for double its planned lifetime,
making it well overdue for retirement.

With ten sophisticated sensors, Envisat has observed and monitored Earth's
land, atmosphere, oceans and ice caps during its ten-year lifetime,
delivering over a thousand terabytes of data.

An estimated 2500 scientific publications so far have been based on this
information, furthering our knowledge of the planet.

During those ten years, Envisat witnessed the gradual shrinking of Arctic
sea ice and the regular opening of the polar shipping routes during summer

Together with other satellites, it monitored the global sea-level height and
regional variations, as well as global sea-surface temperatures with a
precision of a few tenths of a degree.

Years of Envisat data have led to a better understanding of ocean currents
and chlorophyll concentrations.

In the atmosphere, the satellite observed air pollution increase in Asia and
its stability in Europe and North America, and measured carbon dioxide and
methane concentrations. Envisat also monitored the Antarctica ozone hole

Over land, it mapped the speed of ice streams in Antarctica and Greenland.
Its images were used regularly to update the global maps of land use,
including the effects of deforestation.

Using its imaging radar, Envisat mapped ground displacements triggered by
earthquakes and volcanic eruptions, improving understanding of tectonics and
volcanic mechanisms.

Envisat provided crucial Earth observation data not only to scientists, but
also to many operational services, such as monitoring floods and oil spills.
Its data were used for supporting civil protection authorities in managing
natural and man-made disasters.

Envisat has also contributed valuable information to the services within
Europe's Global Monitoring for Environmental Security (GMES) programme,
paving the way for the next generation of satellites.

Now with the end of the mission, the launch of the upcoming GMES Sentinel
satellites has become even more urgent to ensure the continuity of data to
users, improve the management of the environment, understand and mitigate
the effects of climate change and ensure civil security.

For further information, please contact:

ESA Media Relations Office
Communication Department
Tel: +33 1 53 69 72 99
Fax: +33 1 53 69 76 90

[NOTE: Images and weblinks supporting this release are available at
http://www.esa.int/export/esaCP/SEM1...H_index_1.html ]


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