While atmospheric research has long been conducted with satellites, airplanes offer more flexibility: They can descend from altitude, take in situ as well as remote measurements, move in any number of directions (satellites are limited to either east-west or north-south), and loiter over a spot instead of just passing overhead once a day. Even better, scientists can easily swap instruments out for repairs or upgrades. With a satellite, says Chris Naftel, NASA’s Global Hawk project manager, “whatever you put in orbit, you’re stuck with that.”
The Global Hawk does have limitations. NASA’s ER-2 can carry 2,600 pounds; its WB-57, 6,000 pounds. The Global Hawk, by contrast, can carry a payload of 1,500 pounds. Scientists may have to choose a simpler payload than they would for a conventional airplane, says Newman.
The team at Dryden received its first two demilitarized aircraft in 2007. NASA also acquired the last demonstrator, AV-7, in 2009. The fully re-engineered AV-6 has flown all of NASA’s science flights until last May, when AV-1 flew its first NASA test mission.
To train pilots on its three drones, NASA hired a pilot who had flown all of them. Tom Miller had logged some 1,500 hours flying Global Hawks, including with the flight test squadron at Edwards Air Force Base in California and later as part of Operation Enduring Freedom in Afghanistan. “It’s very cool to be asked to come back and fly them again,” he says.
Miller led training for the Pacific mission’s team and flew several of the missions himself. While some of the pilots had experience in manned high-fliers, like the U-2, none had previously flown a Global Hawk. Hall was the only one with a science flight background, having spent about 2,000 hours in NOAA’s Twin Otter.
Global Hawk pilots fly by desktop—in this case, from a brand-new ground station at Dryden dubbed the Global Hawk Operations Center. The center is divided into three compartments: a chilly lobby where air conditioners cool the giant stacks of computer hardware that keep the airplane flying, and two glass-encased rooms, both facing an enormous screen displaying a live camera feed from the aircraft. The pilots work out of the front room; in the back room sit more than a dozen payload operators, keeping their eyes on computer monitors as their instruments stream real-time data to them.
Global Hawk’s track is pre-planned; the aircraft flies on a scheduled airspeed and its bank angles are pre-set, although pilots can make mid-flight adjustments. “Typically—say, 75 percent of the time—we don’t stay on the canned mission plan because our mission objectives are usually things like weather and atmospheric phenomena, which move,” Hall says.
Pilots control the aircraft using four computer monitors, a keyboard, and a mouse. There’s no yoke—not even a joystick. Although they have a moving map that lets them track the aircraft’s progress over remote locations, there’s no feeling of motion. “You lose four of your five senses when you’re dealing with an unmanned vehicle,” says Miller. “You’re not in the airplane, so you don’t feel if the throttle comes back or you don’t feel it when it goes into a turn. Everything is based on sight, looking at the displays.” The pilots have no view out the aircraft’s window.
For the scientists, shifts can be long. Because some interesting bit of data could always come down the pipe, Newman says it was tempting to work long hours and late nights to get the data—“the scientific candy,” he calls it. He used to worry about ER-2 pilots flying over the Arctic: “If the engine flames out, if there is any problem with your ER-2, then you’re not getting that pilot or the plane back. There is no place to land up there, there are no runways, and it’s really brutally cold.” Now, he says, “I don’t have to worry about the pilots anymore—I have to worry about my own team and that they don’t drive off the road because they’re so tired.”
Because science and military missions have different objectives, NASA’s Global Hawk tried some new moves on its first two science flights. According to Chris Naftel, the Air Force had never taken a Global Hawk much past Fairbanks, Alaska, which is around 65 degrees north. Scientists want to get closer to the Arctic, a critical area for studying ozone depletion and other climate phenomena. On the Pacific flights, says Naftel, “we went up to 85 degrees—that’s about 300 miles short of the North Pole.” This is the farthest north a Global Hawk has ever flown.