Recently, officials at the European Space Agency have announced that they will pull the plug on the Envisat mission. While the satellite's failure left them no choice, they are now in a very uncomfortable position in terms of capabilities, which requires them to begin launching the Sentinel satellite constellation.
The loss of ESA's flagship Earth observatory – which, in all fairness, did manage to survive for more than a decade in Earth's orbit – is affecting the agency's ability to supply data to its partners through the Global Monitoring for Environment and Security (GMES) program.
Some of the gaps left by Envisat's yet-unexplained demise can be filled by various collaborations ESA has with other space agencies. However, not all data from the spacecraft are replaceable from other sources, scientists explain, since the vehicle was unique.
The purpose of GMES, “to support European policies and provide decision-makers with key information services,” cannot be fulfilled without the launch of the upcoming Sentinel constellation.
Satellites in this family will be able to provide uninterrupted streams of data for the program, just like Envisat did. At least three Sentinels are scheduled to launch by the end of the decade, with the first one bound to take off in early 2013.
“The quality of MyOcean products, derived exclusively from Envisat’s Advanced Synthetic Aperture Radar and MERIS sensors such as those for monitoring sea ice and ocean water quality, has obviously been affected and the corresponding services have ceased,” expert Joël Dorandeu says.
He works for MyOcean, an organization that provides marine services for GMES. “The quality of monitoring and forecasting model products based on multiple sensors has also been impacted. The situation is particularly critical for the altimetry constellation,” Dorandeu adds.
The Monitoring Atmospheric Composition and Climate (MACC) project, which used Envisat as a main source of data as well, is currently out of commission. Its role was to provide authorities and scientists with an atmospheric methane and ozone concentration monitoring tool.
“Observations of ozone from Envisat’s Sciamachy and MIPAS instruments were routinely used in MACC near-realtime monitoring and forecasting services,” European Centre for Medium-Range Weather Forecasts investigator, Richard Engelen, explains.
“They were used with other instruments, but they were the only ones covering the morning orbit, which allowed the diurnal cycle to be captured better,” he concludes.