UAVs continue to mature with evolving missions

  • 13-Apr-2010 02:41 EDT

The capabilities of Northrop Grumman's Global Hawk lends itself well to support the high-altitude, long-duration Earth science missions of NASA, NOAA, and other partners. The aircraft can fly as high as 65,000 ft and as far as 11,000 nmi.

UAVs have been around since before anyone ever heard the term "baby boomer," and, indeed, before any of those baby boomers, and, in some cases, their parents, were even born. What is different is the sophistication with which they fly amongst us.

What is also different is their missions. UAVs basically had a military mission from the very beginning, primarily as a tool first for surveillance and reconnaissance, and more recently, for attack. Thus, if one had you in its sights, chances are you were not going to have a very good day.

More recently, however UAVs have taken on more benign tasks, including search and rescue and research. In fact, last month NASA completed the first science flight of the Global Hawk over the Pacific Ocean.

The flight was the first of five scheduled in April for the Global Hawk Pacific, or GloPac, mission of studying the atmosphere over the Pacific and Arctic oceans. The GloPac is the result of an agreement between NASA and Northrop Grumman to re-fit and maintain three Global Hawks transferred from the U.S. Air Force for use in high-altitude, long-duration Earth science missions.

Operators pre-programmed a flight path for the GloPac, staying in contact through satellite and line-of-site communications links to a ground control station at Dryden Flight Research Center in the Mojave Desert.

"The Global Hawk is a revolutionary aircraft for science...No other science platform provides the range and time to sample rapidly evolving atmospheric phenomena," said Paul Newman, Co-mission Scientist for GloPac and an atmospheric scientist from the Goddard Space Flight Center. "This mission is our first opportunity to demonstrate the unique capabilities of this plane, while gathering atmospheric data in a region that is poorly sampled."

As part of its mission, the plane carries 11 instruments to sample the chemical composition of the troposphere and stratosphere. Researchers will be directly measuring and sampling greenhouse gases, ozone-depleting substances, aerosols, and constituents of air quality. The instruments profile the dynamics and meteorology of both layers and observe the distribution of clouds and aerosol particles.

One instrument in particular onboard to measure ozone "works by taking a stream of air from outside the plane and passing it into the body of the instrument," said Newman. "The air flows between a lamp that emits ultraviolet radiation and a UV detector. Because ozone strongly absorbs UV, if there is more ozone in the air, then there is less UV at the detector. If there is less ozone in the air stream, then more UV is detected."

Project scientists expect to take observations from the equator north to the Arctic Circle and west of Hawaii. During its first flight the aircraft flew approximately 4500 nmi along a flight path that took it just south of Alaska's Kodiak Island. The flight lasted just over 14 hours and flew up to 60,900 ft. The mission is a joint project with the National Oceanic and Atmospheric Administration (NOAA).

Although the plane is designed to fly on its own, pilots can change its course or altitude based on interesting atmospheric phenomena ahead. 

"The Global Hawk is a fantastic platform because it gives us expanded access to the atmosphere beyond what we have with piloted aircraft," said David Fahey, Co-mission Scientist and a research physicist at NOAA's Earth System Research Laboratory. "We can go to regions we couldn't reach or go to previously explored regions and study them for extended periods that are impossible with conventional planes."

As an added benefit, the timing of GloPac flights should allow scientists to observe the breakup of the polar vortex. The vortex is a large-scale cyclone in the upper troposphere and lower stratosphere that dominates winter weather patterns around the Arctic and is particularly important for understanding ozone depletion in the Northern Hemisphere, according to the researchers.

Scientists also expect to gather high-altitude data between 45,000 and 65,000 ft, where many greenhouse gases and ozone-depleting substances are destroyed. They will measure dust, smoke, and pollution that cross the Pacific from Asia and Siberia and affect U.S. air quality.

"I imagine that in the future there will be fleets of these aircraft probing our atmosphere and providing information for weather forecasting, hurricane reconnaissance, ozone depletion, and climate change," said Newman.

The Global Hawk will make several flights directly under the path of NASA's Aura satellite and other "A-train" Earth-observing satellites, "allowing us to calibrate and confirm what we see from space," said Newman. GloPac is specifically being conducted in conjunction with NASA's Aura Validation Experiment.

The GloPac mission includes more than 130 researchers and technicians from NASA's Goddard, Dryden, Jet Propulsion Laboratory, and Ames Research Center. Also involved are NOAA's Earth System Research Laboratory; the University of California, Santa Cruz; Droplet Measurement Technologies; and the University of Denver.

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