Aeolus, the satellite that measures the wind, was launched

Yesterday at 23:20, after postponement due to strong winds, the launch of Arianespace & # 39; s Vega launcher in the Aeolus orbit, the first satellite to observe the dynamics of the earth's atmosphere, began. This satellite of the European Space Agency, built by Airbus Defense and Space, is intended for measuring winds. A long-awaited measure to improve weather forecasts and to better understand the effects of climate change.

For the fifth launch of the year, the first with Vega, Arianespace has posted job the Aeolus satellite, the first space mission for measuring wind all over the world, on behalf of the European Space Agency. This launch will be the twelfth of thrower Vega, who is demonstrating it versatility and adaptation missions dedicated to earth observation.

There was no shooting period for this mission, which would have allowed some flexibility. If it Vega launcher Not taking off on the second planned, another attempt will take place twenty-four hours later, or later, depending on the cause of the problem and the solution. For this flight the requested performance of the rocket is approximately 1,436 kg, including 1,357 kg in accordance with the take-off weight of the satellite.

The track is synchronous with a separation height of approximately 320 kilometers with a slope of 96.7 degrees. From this orbit, it completes a full turn of the globe every 90 minutes, corresponding to 16 lanes per day and passing the same region every seven days.

Measuring the winds of the earth from space

This satellite, built by Airbus Defense and Space, is the first specially designed to the measure of the wind. Winds are currently being measured from surface stations, at sea and on land, while wind profiles at the highest level are obtained with the help of balloons or from airplanes. But many areas, such as the polar or tropical regions, do not have data at height.

This mission will fill these gaps and provide the data needed to improve the quality of weather forecasts. Wind measurements are calculated quickly so that they can be used by the prognosis operational meteorological. Aeolus will also contribute to long-term climate research and provide information on the optical properties of aerosols in the ultraviolet. Aerosol products can be used in the future to predict the quality of the aerosols.air.

The satellite uses Aladin, a the most advanced instruments ever brought into the job "Declares Dominique Gillieron, head of the Optical Instrumentation Division at Airbus Defense and Space, a Doppler Lidar instrument. laser Ultra-powerful UV, from a big one telescope 1.5 m and very sensitive receptors "This telescope with the amazing peculiarity of" focus both the laser on the emission and that collects the photons from theatmosphere "Its development is so complicated that it explains the decade of program delay, initially Aeolus would be launched in 2007. In the United States, a similar project has been launched" Abandoned by NASA for not controlling the required technology ".

The production of powerful pulses of ultraviolet radiation in the atmosphere, the dissipation and regulation of the heat emitted by the laser and the protection of the optics of the laser against its intensity are the main problems that explain this delay.

To measure these winds, Aeolus uses a " short laser pulse sent from the satellite to the atmosphere ". In exchange molecules of air, water droplets or various aerosols diffuses a part of this radius, and only a small part is scattered back towards the telescope "the speed wind will be obtained according to the line of sight of the scattering particles and then measured by means of spectrometersDoppler effect "The temporal sampling of the measurements makes it possible to know the speed at different heights of the atmosphere.

At last the Aeolus satellite will be so low above the earth, " only about 400 kilometers above the earth ", That he must be protected fromoxygen Atomic. So it will be completely white, " dressed in the same material as the space suits of astronauts ".

What to remember

  • Aeolus, a unique satellite dedicated to wind measurement, was built by Airbus Defense and Space. The European industrial industry overcame technical problems that forced Nasa to abandon the realization of a comparable satellite.
  • For the Vega launcher, this is the twelfth mission since its inauguration in November 2011.

A new satellite to measure the wind

Article published by Rémy Decourt on 22/11/2017

Measuring the wind of a job is the dream of a meteorologist, but no one has been there yet. Airbus Defense and Space is ready to succeed with ADM-Aeolus, capable of firing laser pulses with Aladin, one of the most advanced instruments ever launched in orbit around the earth. This very special satellite is currently undergoing very detailed tests, explains Isabelle Domken, engineer at the Liège Space Center.

A few months before his transfer to Guyana Space CenterADM-Aeolus is currently undergoing its final tests. This satellite of the European Space Agency will be launched in January 2018 by a Vega launcher for an unprecedented mission. It will be the first satellite in the world to deliver Globe-wide wind profiles every day. Currently the wind information is obtained by observing the temperatures on board balloons, so with a low resolution, or by direct measurements that do not cover the entire Globe.

The design of this satellite, a world first, lasted more than ten years. In the United States, a similar project was abandoned because it did not master the required technology. Built by Airbus Defense and Space, it is currently being installed in the Space Center of Liège (CSL) where it undergoes so-called thermal vacuum and space simulation tests. This means that in a tank the spatial conditions are reproduced in which ADM-Aeolus will evolve.

Usually we talk very little these tests in our articles, procedure quite classic in the life of a satellite and perfectly mastered on the ground. This time it seemed interesting to talk about it because the ADM-Aeolus tool will be one of the most advanced ever in orbit. Aladin, his name, includes two powerful lasers, a large telescope of 1.5 meters and very sensitive receivers to measure the speed of land winds in horizontal layers up to 30 km altitude.

The Doppler effect indicates the wind speed

To carry out his measurements, Aladin will use his laser which will transmit short pulses of light intense in the atmosphere. Part of the light backscattered through the molecules of gasdust particles and water droplets are collected by the telescope and sent to the receiver. By analyzing the signal, it is possible to calculate the speed and direction of the air movement at different heights in the atmosphere.

As Anders Elfving notes, Aladin's program directorESA, "We still need to take some crucial steps, we need the ultimate proof that the laser and the complex optical system work well with the thermal radiators of the satellite and under vacuum conditions". Accurate observation of the wind requires many measurements of which the average is calculated. "It costs 700 laser pulses for each wind profile." Isabelle Domken, project manager and engineer at the Liège Space Center explains the role of the CSL and the tests of the Aladin instrument.

Why was the Liège space center chosen to test this satellite?

Isabelle Domken: In 2003 the CSL carried out the first tests on the Aladin instrument. At that time, the Aladin instrument was only tested and was not yet integrated in the satellite. Because the developments of the instrument (including the development of the laser) were delayed, Airbus decided to test the Aladin instrument with the satellite and perform only one vacuum simulation test. The Focal 5 tank had shown an extremely good level of cleanliness during the first tests on Aladin. In 2012 it was decided to change the test set-up (support for the satellite, the thermal tent, the rudder for the satellite) planned for Aladin and pass it on (increases it) to test the complete satellite.

Does the Liège Space Center have special skills to test this satellite?

Isabelle Domken: Yes. And in more than one way.

  • The CSL had the experience and development of the first tests on the Aladin instrument.
  • The CSL has very stable optical banks in vacuum tanks, which enable optical calibrations under vacuum.
  • The CSL can control 14 thermal paths at different temperatures simultaneously. This makes it possible to supply thermal panels at the front of the satellite and to be representative of the conditions of the space that the satellite will see.

What are the laser tests of the Aladin instrument and how do you test it in flight condition?

Isabelle Domken: A laser beam placed outside the tank simulates the return bundle and thus artificially simulates theDoppler effect. This beam passes through a porthole and the vacuum tank moves in the direction of the instrument. In this case, the contamination can be extremely critical: all equipment in the tank has been heated to over 80 ° C for at least 9 hours (even the Kapton type) aluminum).

The presence of oxygen in the tank is a first in the CSL. The satellite does indeed have an oxygen purge on the focal plane. This flow of oxygen prevents contamination from sticking to the optic as the laser UV is enabled (this is the LIC, Induced laser infection). However, oxygen and oil do not mix well: the mixture is explosive. This gas is evacuated by pumps that need to be adjusted, with addition of a rinse to thenitrogen to reduce the amount of oxygen sufficiently. Thermal calculations are made at the level of the thermal panels to the gradients thermal, finite element calculations were performed during the design of the satellite support to one vibration minimum.

How are the tests performed?

Isabelle Domken: Good. The first starts of the laser are in progress. We cross our fingers so that the thermal vacuum calibration of this exceptional satellite is at its best because this object is unique in the world and exceptional in its performance and the results it will offer in climatology.

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