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<\/p>\nArianespace\u2019s lightweight Vega rocket has deployed the European Space Agency\u2019s Aeolus climate science satellite Wednesday in an evening launch from the Centre Spatial Guyanais at Kourou, French Guiana. The mission set sail at the instantaneous launch opportunity timed at 18:20:09 local time (21:20 UTC).<\/p>\n
Aeolus, also known as the Atmospheric Dynamics Mission (ADM) or ADM-Aeolus, is part of the European Space Agency\u2019s (ESA\u2019s) Earth Explorers program which will also contribute to the World Meteorological Organization\u2019s Global Observing System (GOS). Equipped with a Doppler lidar instrument, Aeolus will build a profile of winds in the Earth\u2019s atmosphere below 20 kilometers (12 miles, 11 nautical miles): a range of altitudes covering the troposphere and the lower reaches of the stratosphere.<\/p>\n
The Aeolus satellite was constructed by Airbus Defence and Space. Its design is derived from a platform originally developed for the Mars Express spacecraft, which has been orbiting the red planet for over fourteen years. Aeolus will have a mass at launch of 1,357 kilograms (2,992 lb) and is designed for a three-year operational lifespan.<\/p>\n
Aeolus is three-axis stabilized and will operate in a low circular sun-synchronous orbit \u2013 at an altitude of 320 kilometers (199 miles, 173 nautical miles) and an inclination of 96.7 degrees to the equator.<\/p>\n
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The spacecraft during encapsulation \u2013 via Arianespace<\/p>\n
The launch of Aeolus comes over ten years behind schedule, the result primarily of complications during the development of the satellite\u2019s lidar system. Development of the spacecraft began in 2003, with launch then scheduled for 2007. The EarthCARE mission, which also carries a lidar, was hit by similar delays and is now expected to fly next year.<\/p>\n
Aeolus is also known as Earth Explorer 4, the fourth mission to be commissioned as part of the Earth Explorers program, dedicated to understanding the planet Earth and its climate. The preceding missions in the series were the Global Ocean Circulation Explorer (GOCE) and Soil Moisture and Ocean Salinity (SMOS) \u2013 both launched in 2009 \u2013 and CryoSat.<\/p>\n
The original CryoSat satellite was lost in a launch failure of its Rokot\/Briz-KM carrier rocket in 2005. However, a replacement \u2013 CryoSat-2 \u2013 was deployed by a Dnepr in 2010. With the delays to Aeolus, Earth Observer 5 has launched ahead of it. The three-satellite Swarm constellation was deployed by a single Rokot vehicle in November 2013.<\/p>\n
ESA divides its Earth Explorer missions into two categories \u2013 Core and Opportunity \u2013 with Opportunity missions typically designed to be lower-cost missions reacting to immediate scientific requirements while Core missions are developed in close cooperation with the wider scientific community to answer specific questions about our planet.<\/p>\n
The primary instrument aboard Aeolus is the Atmospheric Laser Doppler Instrument (ALADIN). ALADIN relies on a technique called Doppler Wind Lidar (DWL) to collect wind data.<\/p>\n
Aerospace & Defense (adsbygoogle = window.adsbygoogle || []).push({});<\/p>\n The instrument fires ultraviolet laser pulses at a wavelength of 355 nanometres \u2013 invisible to the human eye \u2013 towards the Earth.<\/p>\n As the light emitted by the laser passes through the atmosphere some photons interact with particles in the atmosphere, causing them to be deflected \u2013 or scattered \u2013 in other directions. ALADIN incorporates a 1.5-metre (5-foot) telescope to collect light that is backscattered \u2013 that is, deflected back towards its source.<\/p>\n Aeolus at work \u2013 via ESA<\/p>\n The satellite will be able to measure several properties of the backscattered photons to understand what has happened to them in the atmosphere. From the time between emission of a light pulse and the photons being received back by the satellite, ALADIN can determine how far the pulse traveled, and therefore the altitude at which the photons were scattered.<\/p>\n The photons will be passed through a spectrometer to build a profile of their wavelengths compared to that of the original light, and the shape of the curve this produces can be used to determine how they were scattered.<\/p>\n Light emitted by ALADIN will be affected by two different types of scattering: if they interacted with gaseous molecules in the air the curve will show evidence of Rayleigh scattering, whereas if they interacted with water droplets in clouds or with aerosols the curves will show that Mie scattering took place. Wind in the atmosphere will cause a Doppler shift in the wavelength of the light, proportional to the speed of the wind.<\/p>\n ALADIN is oriented perpendicular to the satellite\u2019s direction of flight, away from the sun, with the instrument angled downwards \u2013 35 degrees from the vertical \u2013 in order to build up a profile of wind speeds over a strip of the atmosphere as the spacecraft orbits. A single observation will last seven seconds, consisting of 700 pulses, during which time the satellite will travel 87 kilometers (54 miles, 47 nautical miles). There will be a gap of 21 seconds between observations. ALADIN can penetrate thin layers of cloud but cannot observe through thick cloud cover.<\/p>\n The ALADIN instrument via Airbus Defence and Space.<\/p>\n ALADIN is the only primary scientific instrument aboard Aeolus \u2013 although the satellite carries other instruments to aid attitude control and orbit determination. These include the Satellite-to-Satellite Tracking Instrument (SSTI), which uses US Global Positioning System (GPS) navigation satellites to determine the spacecraft\u2019s position in orbit, laser retroreflectors to help observers on the ground track Aeolus and Earth-Sun sensors, star trackers and a magnetometer to keep track of its attitude.<\/p>\n Aeolus flew to orbit atop a Vega rocket. The smallest of the three rockets operated by Arianespace, Vega is a four stage rocket using mostly solid propellants, which first flew in February 2012. The mission is its twelfth flight \u2013 with all of the rocket\u2019s previous launches having been successful.<\/p>\n Italy\u2019s Avio is the prime contractor for Vega, which incorporates three solid-fuelled stages and a small liquid-fuelled upper stage for precise orbit injection. All three solid motors use hydroxyl-terminated polybutadiene propellant, while the Avum burns unsymmetrical dimethylhydrazine (UDMH) oxidized by dinitrogen tetroxide.<\/p>\n Vega launches take place from the Centre Spatial Guyanais in Kourou, French Guiana. The rocket\u2019s launch complex, the Zone de Lancement Vega (ZLV), was built on the site of the former Ensembele de Lancement Ariane 1 (ELA-1) launch pad which was used by twenty-five Ariane 1, 2 and 3 rockets between 1979 and 1986. An even earlier launch pad on the site, CECLES, had been used for a single launch of the Europa II rocket \u2013 an earlier European satellite launch project under the European Launcher Development Organisation (ELDO) \u2013 which failed in 1971. Overall, the launch will be the thirty-eighth from the three pads that have stood on this site.<\/p>\n Vega\u2019s launch pad at CSG \u2013 via ESA.<\/p>\n In preparation for its flight, the Vega rocket was assembled vertically in position at the launch pad. The launch campaign began on 4 July when Vega\u2019s first stage \u2013 a P80 solid rocket motor \u2013 was transported to the launch pad. The interstage between the first and second stages was fitted on 12 July, with the Zefiro 23 second stage being mounted atop this structure the next day. On 16 July the Zefiro 9 third stage was added to the rocket, with the fourth stage \u2013 Avum \u2013 joining the vehicle on 24 July.<\/p>\n While integration of the rocket was ongoing, Aeolus \u2013 which had arrived in Kourou on 28 June \u2013 underwent its own preparations for launch. Following electrical checks, fuelling of the satellite began on 26 July. Between 2 and 7 August the satellite was encapsulated within Vega\u2019s payload fairing, which was transported to the launch pad on 9 August and integrated with the rocket the next day. Fuelling of the Avum stage took place over four days the next week, followed by a launch rehearsal, arming of the rocket and final preparations and inspections.<\/p>\n The countdown for Vega\u2019s launch began nine hours and ten minutes before the rocket was due to lift off. As the clocks ticked towards zero the rocket\u2019s systems \u2013 including the inertial reference system (IRS), multi-functional unit (MFU) and onboard computers were brought online and tested. Three hours and fifteen minutes before liftoff the mobile gantry used to assemble and access the rocket was retracted away from the vehicle \u2013 a process that took about three quarters of an hour to complete.<\/p>\n<\/p>\n![\"\"](\"https:\/\/www.nasaspaceflight.com\/wp-content\/uploads\/2018\/08\/2018-08-22-152503.jpg\")
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