Discovering the secrets of our planet

Jason-3 was launched on January 17th, 2016. It took over from Jason-2 in October of that year. The satellite became part of a large Network of NASA satellites, looking at sea Levels and at oceanic and atmospheric currents.

Level recorders installed at shore can't answer that question. However, satellites can recognize continental shift. That's why NASA launched its Ocean Surface Topography Mission (OSTM) using the satellites Topex/Poseidon, Jason-1, -2 and later -3 to solve the mystery. Jason-2 sent us topographical radar images, and its successor Jason-3 has additional tools on board -- a radiometer and a laser.

Without Earth observation satellites, we would not understand our planet as well as we do now. Sentinel-2 took this picture of the northern shore of the Adriatic with the Italian Alps in late June, shortly after its launch. Sentinel-2 is part of the European Space Agency's (ESA) comprehensive Copernicus Earth observation program.

Sentinel-2 uses a spectrometer, which is a special camera that can take pictures at numerous light wavelengths. This enables scientists to see all kinds of details in pictures that you can't detect with the naked eye, including the status of vegetation or the moisture in the soil. Here, engineers are preparing the satellite for its journey.

A view of Northern Italy: The city of Pavia in the upper left corner with the river Ticino flowing into the larger Po. The infrared spectrum of the camera reveals the state of the agriculture: Scientists can even see what is growing on the fields - is it corn, wheat or pumpkins on this one?

Many Earth observation satellites are not alone in their mission; they do their job better as a team. This is also true for Sentinel-1 and -2, which eventually will each get a support satellite. Together they can document every spot on the surface of the planet every five days. The Copernicus Program includes six modules (Sentinel-1 through -6) for all kinds of tasks.

One task is measuring the topography of the land, just as Jason-3 does with the sea. Sentinel-1 is built for that, with its large radar antennas. It can detect hills, mountains and valleys. The data the satellite generates can later be combined with the data from Sentinel-2 or other satellites. This gives farmers, developers and environmental agencies exactly the information they need.

The radar-eye of the satellite took this picture of the Dutch coast. It shows that the country is not as flat as many may believe. Dunes, buildings and levees can be clearly seen.

ESA's SWARM mission is a whole different type of Earth observation: Three satellites are circling the Earth, looking deep into the core of the planet. The SWARM satellites have been recording changes in the magnetic field of the Earth since 2013.

Scientists are interested in the Earth's magnetic field because it is constantly changing. Under the Earth's crust, magma is constantly moving and changing the magnetic makeup. Even the magnetic poles sometimes swap places. Knowing this is extremely important for the sea and air navigation.

Earth magnetism also affects our relationship to the sun. The magnetic field shields us against cosmic and sun rays, which can be particularly strong after sunspot eruptions. If the Earth's magnetism changes, it also changes the way particles from solar rays travel around the Earth's poles. Satellites looking toward Earth can sometimes reveal these secrets from far away.