ESRL Quarterly Newsletter - Winter 2009

Soaring for Science

NOAA-NASA unmanned craft to soar over Pacific Ocean this spring

An unmanned aircraft with wings stretching 116 feet soared into the air over NASA’s Dryden Flight Research Center in October, in preparation for its first science mission in February. The Global Hawk Unmanned Aircraft System (UAS), built by Northrop Grumman Corp. and operated jointly by NASA and NOAA, will take at least six long-duration flights as long as 30 hours above the Pacific Ocean this spring, in a mission dubbed GloPac, for Global Hawk Pacific. A groundbased crew will guide the aircraft from the equator to the Arctic Circle, as remotely controlled scientific payloads on board collect data on key regions of the atmosphere important in climate change and ozone layer research.

Researchers on the ground will be able to watch their data arrive in near real-time via satellite link, and can redirect the aircraft to certain phenomena or regions of interest along the flight track.

“This first Earth science mission of the Global Hawk will demonstrate the value of this unique and powerful resource to atmospheric science, to our national agencies, and to the world,” said ESRL’s David Fahey (Chemical Sciences Division), one of two GloPac mission scientists (with Paul Newman from NASA Goddard Space Flight Center).

In October, the Global Hawk completed several successful test flights in controlled airspace above Edwards Air Force Base, spiraling up to about 61,000 feet in altitude. The aircraft is one of two that NASA and Northrop Grumman have partnered on to convert from military test aircraft to scientific and aeronautical research platforms. Before October’s flights, neither had been in the air for more than six years.

“That’s a big story from our perspective,” said Global Hawk pilot and NOAA Corps officer CDR Philip Hall. “In 18 months, we’ve taken an airplane that sat on the ground for six years and we made it flyable with a completely new communications system and ground control station optimized for scientific payloads. These programs normally would take years, and a lot more money.”

In February, scientists will travel to Dryden to install sophisticated instruments on the airplane, including two from ESRL—one to measure ozone and the other to measure a variety of gases in the atmosphere. Jim Elkins (Global Monitoring Division) is principal investigator on UCATS, the Unmanned aircraft systems Chromatograph for Atmospheric Trace Species, which measures water vapor, ozone, nitrous oxide, sulfur hexafluoride, hydrogen, methane, and carbon monoxide. Ru-Shan Gao (Chemical Sciences Division) is in charge of the dedicated ozone instrument on board.

“As with David Fahey, these guys are all world-class leaders in atmospheric science. They have vast backgrounds in flying their instruments on a variety of airplanes, so they bring a lot of experience and knowledge to the program,” Hall said.

One of the science goals this spring, Fahey said, will be to investigate what happens to the Arctic polar vortex as it breaks up. In winter, high-altitude winds tend to sweep around the pole, isolating high northern latitudes chemically as well as dynamically. When the vortex breaks up every spring, it can spin fragments of Arctic air to lower latitudes and altitudes, providing opportunities to sample the chemical nature of Arctic stratospheric air and to test models that simulate atmospheric air motions.

The Global Hawk will also “underfly” a suite of NASA satellites, specifically, the Aura satellite, to provide “ground-truth” data for comparison with atmospheric measurements taken from space, Hall said.

Hall described the GloPac mission as a “hybrid” of satellite and aircraft capabilities, with a field of view somewhere in between the two. The extreme range, duration, and altitude of the Global Hawk’s flight envelope give it remarkable capabilities for the scientific community, not previously obtainable,he said.


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