Watching Over Us

Nothing escapes their gaze: The new Sentinel satellites are set to explore our home planet more comprehensively than ever before, saving thousands of human lives in the process. The big difference between them and their predecessors: For the first time, a

Sentinel satellites will show us the world in whole new ways

On June 23, 2015, at exactly 10:51 P.M. local time, the countdown is concluded. Spellbound researchers at the European Space Agency (ESA) stare at the screens in the control center as a harsh arrow of light rises through the clouds in the night sky. After seven years of preparations, they finally achieved their objective: A Vega rocket has blasted off from a spaceport at the tip of French Guiana. This launch marks the beginning of phase II of the most ambitious Earth research program in human history. That’s because aboard this rocket is a satellite that will forever alter our view of our own planet. Its name is Sentinel-2a, and its groundbreaking innovation compared to all previous satellite missions is that for the first time anyone can download its data from the Internet—so anyone can be a guardian of the Earth…

HOW DO YOU SEE THE INVISIBLE?

“We are standing on the verge of a new era of terrestrial observation,” says Helmut Staudenrausch of the German Aerospace Center. In 2014 the first representative of this new generation of satellites, Sentinel-1a, was shot into space, and this past February 16 saw the launch of the Sentinel-3a—and more will follow. In 2021 a family of these guardians will be circling Earth, its members functioning like interlocking gears, which will enable them to precisely monitor our planet’s land surface, oceans, and atmosphere as well as how these natural systems interact. The Sentinels are part of the ESA’S $7 billion Earth Observation Program known as Copernicus.

With the help of high-tech radar, the 2.5-ton Sentinel-1a satellite can scan Earth’s surface in all weather conditions—and around the clock. The primary focus of the watchman: For seven years it will orbit Earth at a distance of 430 miles and chart the amount of sea ice at the poles. Scientists are hoping that the data will help them provide more precise predictions about rising sea levels. In addition, the ice maps can reveal the thickness of the sea ice, which can make navigation easier for ships and thereby help prevent accidents. In 2016 a structurally identical twin of the satellite will start to circle the Earth in a 180° staggered orbit so as to double the recording capacity.

Unlike Sentinel-1, which observes the oceans, Sentinel-2a, which was launched last June, specializes in land surface. But this more recent unit has a key advantage when compared with its predecessor: As 2A flies around Earth at a speed of 4.3 miles per second, it is utilizing high-resolution spectral images rather than radar to scan the globe. As a result, the satellite sees both the spectrum that’s visible to us, which encompasses red, green, and blue wavelengths, as well as the infrared spectrum that’s invisible to the human eye. Sentinel-2a can therefore deliver information about Earth’s surface that would remain hidden from radar waves. This gives rise to a host of new possibilities, especially with regard to improving harvest forecast accuracy, because: “The infrared range is particularly sensitive to changes in vegetation, for example, the growth of forests, ” explains Michael Rast of the ESA’S Earth Observation Program.

CAN A SATELLITE HELP CONVICT ENVIRONMENTAL TERRORISTS?

The guardian takes 100 minutes to orbit Earth once. This year it will be getting some backup from its twin, Sentinel-2b, and at that point the flyover time for each point on the planet will become halved, from 10 days to five.

The unique aspect of ESA’S Copernicus program is its open data concept: Unlike satellites for military reconnaissance that supply secret data, information collected by the Sentinels will be freely available on the Internet. Anyone can take part in this project—a milestone that’s comparable to the dawn of the World Wide Web in 1991. “This will surely trigger a small revolution,” declares Heinz Sontag, a project manager at the company Airbus Defence and Space, which partnered with the ESA to build the new satellite. The research is sure to benefit from such “crowdsourcing”; every day Sentinel-1a alone sends 8,000 gigabits to Earth—a flood of data that a single institution would hardly be able to process on its own. But a multitude of voluntary users

“Using radar, the satellite can see when a ship emits oil residues into the sea.”

Volker Liebig, ESA director of EOP

could actively support scientists in analyzing data, and individual users could possibly even make their own discoveries, as amateur astronomers have already been doing for years. The numbers seem to be adding up: Around 7,700 users have registered so far and a total of 1.4 petabytes of data was downloaded. No surprise: By evaluating these images anyone can inspect Earth’s surface for signs of climate change right from home, for example, or scour the oceans for aircraft wreckage or oil spills.

Thanks to imagery from satellites, any Coast Guard can already react swiftly in the event of a ship breaking down or an accident at sea, and satellite images also facilitate detection of a ship that’s illegally releasing pollutants into the sea. But the eyes in the sky can do more than watch Earth and track down criminals—they can also lend a hand in disaster-relief work.

HOW FAST CAN SENTINEL SUPPLY LIFE- SAVING INFORMATION?

Last April when Nepal was hit by a devastating earthquake, governments and aid organizations were able to rely on satellite images to assess the terrain and figure out logistics such as how workers could access the crisis zones and where helicopters would be able to land. Whereas previously it took 30 hours for experts to compile the data into a meaningful satellite image, in the future it should be possible to predict disasters much more precisely and to react to them much more quickly. Image data could be available within 20 minutes. And through the use of infrared transmission, it should also be possible to send data to Earth in real time. In fact, Sentinel-2a already has the appropriate laser terminal. Beyond the time that’s being saved, the high resolution of the images also opens up entirely new possibilities: “We’ll be able to say, this part of the city is flooded out but that ball field over there isn’t,” says meteorologist Javier García-pintado. Still, many experts sense danger in Sentinel’s versatility… What if the satellites were to be utilized for secret military purposes— for instance, spying on troop movements or even monitoring the flow of refugees? Michael Rast of the ESA refutes the idea: “You’d need a higher ground resolution to be able to track the journey of refugees. For this purpose spy satellites are much more appropriate.” Volker Liebig, director of the ESA’S Earth Observation Program, thinks Sentinels could actually help save lives by discovering refugee boats more quickly—in which case they’d be living up to their name yet again. After all, the Sentinels’ mission is to guard the Earth and its inhabitants, rather than to surveil them…

“We seek to observe Earth continuously and in real time so we can react to catastrophes right away.”

Michael Rast, ESA scientist