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Europe Is Launching Sentinel-3A, the Latest in Its All-Seeing Satellite Network

The Earth observation satellite will focus its gaze on the oceans.

On Tuesday, the European Space Agency will launch the Sentinel-3A satellite: a new eye in its ambitious Earth observation constellation that will focus its gaze primarily on the oceans.

The Copernicus programme, headed by ESA and the European Commission, aims to keep tabs on the "health" of our planet; it encompasses six different types of Sentinel satellite that host different Earth observation instruments, with data fed into six main "services," from security to climate change.


"It's a huge programme; it's not just a single mission," said Sentinel-3 Mission Manager Susanne Mecklenburg in a phone call.

"The idea of Copernicus is to provide continuity to data sources we have had before—for example with Envisat," she explained. Envisat was a satellite launched by ESA in 2002 that housed a whole host of Earth-observing instruments but which became space junk after ESA lost contact with it in 2012.

Sentinel-3A on the way to the launch pad at Pletsesk. Image: ESA–Stephane Corvaja, 2016

The Sentinel satellites pick up where some of Envisat's instruments left off, with Copernicus also making use of other data to offer a single comprehensive Earth monitoring system. Sentinel-3A will be of most relevance to the programme's marine monitoring service.

Unlike the previous two Sentinels, Sentinel-3 has not one but three main instruments. The Ocean and Land Colour Instrument (OLCI) is an imaging spectrometer that can help "see" things like vegetation on land and algal blooms in the ocean; the Sea and Land Surface Temperature Radiometer (SLSTR) will measure the surface temperature of land and sea; and an altimeter instrument will measure the height of oceans, rivers, and sea ice.

"These are very distinct, different instruments but you can also use them in good synergy with each other, and that's also a very important thing," said Mecklenburg. "For instance, over oceans you would have sea surface height, you would have sea surface temperature, and you would have, let's say, algal bloom information of marine biology. If you combine those things there's a much bigger variety of applications you can cover."


The measurements could be useful for myriad applications, from monitoring the effects of climate change and forecasting the weather to guiding more efficient water management. The data from Copernicus will also be freely available so scientists, government bodies, and other individuals and institutions can find new uses for it.

Sentinel-3A is set to launch at 17:57 GMT from Russia's Plesetsk cosmodrome. After it's completed a commissioning phase of around five months, it will be routinely operated by Europe's meteorological satellite organisation Eumetsat.

All being well, it will be joined by its sister satellite Sentinel-3B in 2017 to provide greater coverage, with further Sentinels poised to launch in 2021.

Mecklenburg emphasised that on top of the satellites, Copernicus comprises data from other complementary missions and brings together consortia of users to turn the information collected into the different services offered. "In parallel to developing a space segment, the Commission also developed a user base that will use these data," she said. "So it all comes together in some way—it's several orders of magnitude larger than just designing for one mission."