can contribute to this critical mission.”
Funded by the European Space Agency and built by Airbus Defense and Space, the 480 million euro ($550 million) Aeolus mission is nearly two decades in the making. Since receiving ESA’s formal go-ahead in 2002, Aeolus has suffered numerous delays as engineers encountered problems with the mission’s laser instrument.
Aeolus will gather the first comprehensive worldwide measurements of wind speed — over oceans and land masses — from Earth’s surface to an altitude of nearly 100,000 feet (30 kilometers).
Data collected by the Aeolus satellite will be fed into numerical weather prediction models, replacing simulated “boundary conditions” in the computers models with near real-time measurements from space.
“We are serving the meteorological community as the primary user, but also the climate research community,” said Anders Elfving, Aeolus project manager at ESA. “For decades, there has been an outcry from these communities for explicit wind measurements, explicit wind profiles in the whole atmosphere, globally and continuously.”
Aeolus was not conceived by ESA as an operational weather satellite, but forecasters will be some of the prime beneficiaries of the mission. The mission is named for a figure in Greek mythology who was appointed by the gods as “keeper of the winds,”
“We have a unique product which can be — if proven to the right quality — directly injected into the weather models,” Elfving said in a phone interview with Spaceflight Now before the launch. “Our main client is the ECMWF, the European Center for Medium Range Weather Forecasts … in the UK, and they will certainly inject our data straight into their model and get a lot of good boundary conditions for winds, which are today completely missing.”
Aeolus carries a high-power ultraviolet laser fired at 50 pulses per second toward the ground. Light emitted from the laser — the centerpiece of Aeolus’s single science instrument — will bounce off air molecules, aerosol and cloud particles, and Earth’s surface.
A tiny fraction of the scattered ultraviolet photons will reflect back toward a 5-foot (1.5-meter) telescope on the Aeolus satellite.
“Aeolus actually has its own sun on-board in the sense that it’s sending out laser light into the atmosphere, and this laser light is then scattered back from air molecules and particles in the atmosphere,” said Anne Grete Straume, ESA’s Aeolus mission scientist.
The light will return to the Aeolus satellite’s Atmospheric Laser Doppler Instrument — ALADIN — with a slightly different color. By analyzing the change in color caused by the motion of atmospheric air molecules — known as the Doppler effect — scientists can derive wind speeds.
The Doppler effect is the same process that causes an ambulance’s siren to sound different when it approaches and drives away.
“The same happens to the light which is sent out by the satellite,” Straume said in an ESA video interview. “The movement of the air molecules and the particles in its path will actually stretch or compress the light wave, and you get a different color coming back to the instrument.
“We measure the back reflection of the air and the particles at different ranges from the instrument, and from this you can actually measure the winds at different altitudes through the atmosphere from the surface up to the stratosphere,” she said. “About 30 kilometers is the top level that we will be able to measure.”
No other space mission has been able to measure winds at multiple layers of the atmosphere on a global scale. Previous satellites have been limited to deriving winds measurements by tracking the movement of clouds and aerosols, or by measuring the effect of winds on the ocean surface.
But Aeolus will be able to measure wind speeds in clear skies, eliminating the limitations of other missions. Meteorologists currently use weather balloons and airplanes for wind data, but the observations are spotty.
Wind measurements from Aeolus “will fill a significant gap in the wind observing system, particularly in the upper troposphere, the lower stra