NASA Global Hawk Winds Down Hurricane Studying Mission

    
        
            
        
        
            
        
    

HS3 Principal Investigator Robert Braun shows a dropsonde. AUVSI photo.

By Brett Davis



NASA is winding up the final flying days of its five-year Hurricane and Severe Storm Sentinel mission, or HS3, as it watches Hurricane Edouard in the Atlantic.



The goal of HS3 was to better understand how hurricanes and other storms form and change, including the tricky question of whether wind and sand blowing off the Sahara Desert — called the Saharan air layer — aids in the formation of hurricanes or suppresses it.



“It’s a very hot, dry dusty air mass that comes off of Africa,” Robert Braun, the HS3 principal investigator, said at a press and public event held at Wallops on 11 Sept. “There’s a bit of a controversy about whether they help formation or suppress formation. We’re trying to resolve some of these issues about what exactly the role of the Saharan air layer is.”



NASA has been flying its two Global Hawk unmanned aircraft out of its Wallops Flight Facility in coastal Virginia for three of the five mission years. Last year both of the high-flying UAS were in residence at Wallops, but this year electrical gremlins kept AV-1, the very first Global Hawk built, grounded in California. NASA did fly AV-6, the sixth Global Hawk ever built.



The aircraft carries three cameras that help the pilots know what it’s doing (most of the flying is autonomous, however) as well as three scientific instruments: a lidar system that bounces a laser off clouds and dust to build a map of the storm, a scanning high resolution infrared sounder that profiles the air and a dropsonde system that releases dozens of small, lightweight tubes that measure humidity and temperature. By tracking the dropsondes’ GPS locations on the way down, NASA can also measure wind speed and direction.



“That’s probably our most valuable payload,” Braun said.



AV-6 conducted four flights so far this year and Braun said NASA hopes to squeeze in a few more over Edouard before the flying portion of HS3 comes to an end in late September.



Those flights demonstrated the Global Hawks’ range. One was a transit from California, which included a look at Hurricane Cristobal, which was over the Bahamas. The second flight was another look at Cristobal, which changed as it moved to high latitudes.

There is still a lot of data to plow through so the HS3 work will continue on the ground, but the flying action will now shift to NOAA, the National Oceanic and Atmospheric Administration, which plans to fly the Global Hawks to study cold-weather storms in the Pacific Northwest and Alaska.



“What really sets HS3 apart is the multi-year nature of this,” said Jack Kaye, the associate director for research, Earth Science Division. 



In the past, researchers might go out for four to six weeks to study storms, then a couple of years later they would go somewhere else, he said. The ability to go back to the same place “is something we’ve not really had before.”



HS3’s biggest problem was a good one to have, at least for those people on the ground: Not enough hurricanes. The flying years of HS3 were not busy hurricane seasons, as it turned out, enough so that Braun joked that HS3 seemed to be a hurricane deterrent.