Aeolus, the first satellite that observes the winds from space

Aeolus, le premier satellite qui observe les vents depuis l'espace

Aeolus, le premier satellite qui observe les vents depuis l'espace

By Jeremy Wilks
& Stephanie Lafourcatère

In this edition of Space, our reporter Jeremy Wilks is located on the northern coast of Norway, at the space Centre of Andøya. He meets scientists who are working on a new satellite, called Aeolus. Its mission : to measure for the first time, the winds around our planet. Currently, the team is trying to calibrate and validate all the measures that they receive from space.

The roar of the Vega rocket marks the beginning of a revolutionary mission for weather observation. At the end of August, the long-awaited Aeolus, a satellite of the european space Agency (ESA) has joined the space to place just 320 kilometers above our heads.

_”Aeolus is spinning around the Earth at a time when we are talking about : it moves from the North pole to the South pole before returning to the North pole, it has what is called a polar orbit,”_ says Anne Grete Straume, scientific support for the Aeolus mission the ESA. “And while it revolves around the Earth,” she says, “the Earth also revolves : what makes Aeolus carries out measurements around the Earth 16 times per day.”

Laser technology

Aeolus evaluates thanks to a laser system called Lidar, the direction and speed of winds from space. A first.

No space mission cannot be carried out alone, the scientific team based in Norway, is there in support. The spatial Center of Andøya, an observatory atmospheric with several instruments, is a site unique, is situated 300 km north of the arctic circle.

The data collected on-site will play a key role in the calibration and validation of the surveys on the winds from space.

“When you look at the situation of our observatory at 69 degrees north, there is no other who is able to make measurements in collaboration with Aeolus,” noted Michael Gausa, director of research at the space Centre of Andøya. “This is really the only site that takes measurements Lidar on the speed and direction of winds at this latitude in the northern hemisphere,” he says.

Ground-based measurements in addition

On the site, there are two telescopes owned by the Leibniz Institute of atmospheric physics, which work as the new european satellite : they use lasers to observe the wind. Anne Grete Straume of ESA can refer to as you make comparisons in the context of the Aeolus mission.

“It is very important to check that the measurements of the satellite that we receive are accurate for any type of weather such as storms that trigger or good weather,” says Anne Grete Straume. “We need to compare them with these measures of quality that are performed on the ground and that relate to any type of weather and it is for this reason that it is important not to achieve a measure and compare it, but to realize and compare the continuous measures,” adds the scientist.

Other types of data are used to assess the accuracy of the instruments Aeolus as those from balloons and weather on the Norwegian website, are launched twice a day. They collect local measurements on the wind speed, the temperature and humidity that are found to be key parameters to forecast the weather.

“Thanks to these balls, we collect measurements on the wind in situ : it is very important to calibrate and validate the measurements of the satellite,” says Ingrid Hanssen, engineer of the directorate at the space Centre of Andøya. “Like this, one can know that it performs readings in roughly the same area : of course, the ball is pushed by the wind, but we know that we have the same global coverage and we can compare the measurements of the satellite with those of the ball,” she said.

“We have very little data on the wind”

Aeolus is far from being the only satellite weather in space : they are many to scrutinize the temperatures and the humidity.

So far, no system or wind measurement does not exist for the time scale of the planet. You can see the clouds, but not the movements atmopshériques.

The wind is the missing piece of the puzzle of the weather after Lars Isaksen european Centre for medium-range weather forecasts (ECMWF) : “Some of the largest forecast errors the last five years have had a link with our lack of knowledge about the winds in the tropics,” he says. “We have no information on winds over oceans like the South Pacific and even in the Atlantic, we have very little data on the winds,” he says.

The measures of Aeolus the winds will be routed by this facility to be processed and corrected in the light of other reports of weather before being transmitted to the forecasters.

Still, this mission of the ESA is a test : it must still be proven. “Nobody knows for the moment if it is going to work,” admits Lars Isaksen. “If everything works well, we will integrate the data in our numerical models prediction to have more information on the initial situation – this is the time that it is today,” he says. “It all depends on the time that it is today : one informs these conditions in a complex mathematical model that advance in time and we obtain a forecast for the coming days,” explains he.

“It’s really exciting”

Aeolus is capable to measure the speed and direction of the wind from ground level up to 30 km altitude. Until now, his instrument laser fairly delicate seems to work as expected.

“A few weeks after the launch in space and verification of the satellite and of the instrument, it has started and it is already starting to receive data that are similar to what we will have in the end : so it really is promising !” enthusiastic Anne Grete Straume, ESA.

In the future, when scientists will have at their disposal several years of data, they hope to use Aeolus for the analysis of the climate and of long-term trends.

“As the climate changes currently, the temperature difference between the Equator and the poles is reduced, and this also changes the way the winds behave in the atmosphere and transport energy,” says the scientist in charge of the mission. “So if we can understand this in more detail, we will be better able to know how the weather will evolve in the climatic conditions that there will be in the future,” she hopes.

If the Aeolus mission is a success, other satellites of the same type could be launched to take over.