tosphere, in the tropics and over the oceans, where in situ wind observations are lacking,” scientists Michael Rennie and Lars Isaksen from the ECMWF wrote in a blog post earlier this month.
Researchers also intend to analyze data from Aeolus to gain a better understanding of how winds are generated, and how atmospheric currents are linked to changes in Earth’s climate.
“The winds are connecting all the areas together,” Straume said. “It’s transporting air from one place to the next, and it’s also what you feel on the ground, which will actually feed into the storms and the weather.
“There will be scientific users who want to learn more about winds, the relationship between wind, temperature and pressure, and also climate modelists in order to make these long forecasts into the years to come,” Straume said. “They need to understand how the wind is working, and they will pick up our data.
“I’m really looking forward to the first light coming back through the instrument, and being sent down to Earth and analyzed, and we will see what the instrument really can do,” she said. “And I’m looking very much forward to the first wind observations and these bineg used by the weather forecast models.”
As the satellite orbits nearly 200 miles above the Earth, Aeolus will point its ultraviolet laser beam at an angle of 35 degrees to the side of its ground track, in the direction away from the sun.
Aeolus launched into a “dawn-dusk” polar orbit, meaning the spacecraft will roughly follow the boundary between day and night as it travels in a north-south direction, circling the planet every 90 minutes or so.
“We are actually shooting our laser pulse in a slant angle of 35 degrees perpendicular to the orbit, and measuring the line-of-sight return wind speed,” Elfving told Spaceflight Now. “For all purposes, the vertical winds are very small with respect to horizontal winds. So what we’ve promised to give are horizontal line-of-sight winds, which in practice means, more or less, the east-west wind all over the world. That may sound limited, but when meteorologists but that boundary condition of that vector into their overall wind models, they get 75 to 80 percent knowledge of the total wind vector.”
The long wait has not tempered expectations for Aeolus.
“We were initially promising that we would be flying in 2007, or at least in early 2008,” said Elfving, who became Aeolus project manager in 2010. “Yes, we have had a 10-and-a-half or 11-year delay. My director said we are not ashamed at all of that. We are very proud to have sustained through all the troubles because there is actually no other comparable mission implemented in the world.”
Engineers determined Aeolus needed an ultraviolet laser to give Aeolus the capability to monitor global winds. A laser operating in visible wavelengths, such as the laser aboard the U.S.-French CALIPSO satellite, would only be tuned to track cloud motion.
Ultraviolet lasers flown in space on previous tech demo and Earth science missions have not succeeded. Most recently, an ultraviolet laser on NASA’s Cloud-Aerosol Transport System instrument on the International Space Station failed soon after it was activated in 2015.
Some of the major challenges that faced the Aeolus team included selecting materials that can cope with the high-temperature output of the laser.
“We pulse our optics 50 times every second, and this goes on year after year, and this intense pulse creates 1,700 degrees on the optical surface of the optics, and will fatigue the optics in the long run,” Elfving said. “So we have had tremendous development of the coatings of the optics to withstand this high laser pulse. We are actually our own sun.”
Managers ordered one of the most significant redesigns of the ALADIN instrument aboard Aeolus to ensure the sensor’s optical surfaces remain free of contamination.
“If there are some remaining hydrocarbons on the surface of the optics, and the UV light hits it, it will carbonize, so blacken, the surface and reduce dramatically the reflection or transmissibility of the optics,” Elfving said. “That