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- 10/05/2012, 10:56 #1
Goodbye Envisat ... and thank you
Comunicado de la ESA.
Dear ESA data users,
Just weeks after celebrating its tenth year in orbit, communication with the Envisat satellite was suddenly lost on 8 April. 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.
The team has been collecting other information to help understand the satellite's condition. These include images from ground radar and the French Pleiades satellite. With this information, the team has gradually elaborated possible failure scenarios. One is the loss of the power regulator, blocking irreversibly telemetry and telecommands. Another scenario is a short circuit, triggering a 'safe mode' - a special mode ensuring Envisat's survival. A subsequent anomaly may have occurred during the transition to safe mode, leaving the satellite in an intermediate and unknown condition. The investigation team's assessment is that the chances of recovering Envisat are extremely low.
Therefore the end of the Envisat satellite operations is being declared. The investigation team will nevertheless 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. Envisat provided crucial Earth observation data not only to scientists, but also to many environmental services, such as monitoring floods and oil spills.
Now with the end of Envisat's 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.
See also Press Release on the ESA Portal at ESA Portal - ESA declares end of mission for Envisat
Envisat’s Advanced Synthetic Aperture Radar (ASAR) captured this image on 8 April 2012 at 11:09 GMT. The image was transmitted in X-band to the Santa Maria station in the Azores, Portugal, operated by Edisoft. It shows Spain’s Canary Islands. It is the last Envisat data transmitted via X-band before the communication anomaly.
This animation shows radar images from the Envisat satellite from 2002 to 2012 of the Larsen B ice shelf in Antarctica. Over the last decade, the ice shelf has disintegrated by 1790 sq km.
Envisat captures Cyclone Nargis making its way across the Bay of Bengal just south of Myanmar on 1 May 2008, with its Medium Resolution Imaging Spectrometer (MERIS) instrument working in Reduced Resolution mode to deliver a spatial resolution of 1200 metres. Pincha aqui para verla en alta resolución.
This Envisat image over the North Sea captures numerous aircraft condensation trails, or 'contrails', as well as parts of the Netherlands (upper right), Belgium (lower right) and England (lower left). This image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on 21 March 2009, working in Full Resolution mode to provide a spatial resolution of 300 m. Pincha aqui para verla en alta resolución.
Última edición por Ce_Zeta; 10/05/2012 a las 11:25 Razón: imagenes
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