For the first time, NASA has begun flying an unmanned aircraft outfitted with scientific instruments to observe the Earth's atmosphere in greater detail. The agency has partnered with Northrop Grumman to outfit three aircraft, called Global Hawks, which were given to NASA by the U.S. Air Force. Unlike manned aircraft equipped with Earth observation tools, the Global Hawks can fly for up to 30 hours and travel for longer distances and at high altitudes; they can also gather more precise data than satellites and can be stationed to monitor an area for extended periods of time.

Robo-plane: NASA and Northrop Grumman have developed this unmanned aircraft equipped with scientific instruments for earth science missions. Called Global Hawk, NASA acquired the airplane from the U.S Air Force and modified it to carry instruments to monitor the atmosphere more precisely than satellites can.
Credit: NASA
"There are certain types of atmospheric and earth science data that we are missing, even though we have things like satellites, manned aircraft, and surface-based networks," says Robbie Hood, director of the National Oceanic and Atmospheric Administration's (NOAA) Unmanned Aircraft Systems program. NOAA has formed an agreement with NASA to help construct the scientific instruments and guide the science missions for the Global Hawks. Hood will evaluate the aircraft to determine how they could be best used. For example, she says, they could fly over a hurricane to monitor its intensity changes or fly over the arctic to monitor sea ice changes in higher detail.

The Global Hawks' first mission launched last week--an aircraft flew from NASA's Dryden Flight Research Center at Edwards Air Force Base in California over the Pacific Ocean. The project scientists will launch approximately one flight a week until the end of April. The drone is outfitted with 11 different instruments to take measurements and map aerosols and gases in the atmosphere, profile clouds, and gather meteorological data such as temperatures, winds, and pressures. It also has high-definition cameras to image the ocean colors.

"The first mission is mostly a demonstration mission to prove the capabilities of the system," says Paul Newman, co-project scientist and an atmospheric physicist at NASA Goddard Space Flight Center in Greenbelt, MD. The aircraft will also fly under the Aura Satellite, a NASA satellite currently studying the Earth's ozone, air quality, and climate, to validate its measurements, making a comparison between its readings and what the new aircraft can do. "Satellites give you global coverage every day, but they can't see a region very precisely. The aircraft can give you regular observations and very fine resolution," says Newman.

The robotic airplanes operate completely autonomously--scientists program the plane prior to departure with the intended destinations, and the plane navigates itself. However, scientists can change the aircraft's flight path once in route or remotely pilot it in an emergency. Because a Global Hawk flight can last 30 hours (compared to 12 hours for a manned flight), the aircraft can travel to regions, such as the arctic, that are typically too dangerous for manned missions.

Autonomous flier: The airplane’s first mission is to monitor the atmosphere above the Pacific Ocean. It can fly for up to 30 hours, reach an altitude of 19.8 kilometers, and travel a range of 22,800 kilometers.
Credit: NASA

NASA acquired the aircraft from the U.S. Air Force in 2007. They were originally developed for surveillance and reconnaissance missions. Now researchers are modifying them for their first extensive earth science missions. "We can get high resolution in situ measurements, and that is really the gold standard, and something that we have never before been able to do," says Randy Albertson, director of NASA's Airborne Science Program in the earth science division at Dryden.

The instruments onboard for the first mission include: a LIDAR instrument that uses a laser pulse to measure the shape, size, and density of clouds and aerosols; a spectrograph that measures and maps pollutants like nitrogen dioxide, ozone, and aerosols; an ultraviolet photometer for ozone measurements; a gas chromatograph to calculate greenhouse gases; a handful of other instruments that can accurately measure atmospheric water vapor and ozone-depleting chlorofluorocarbons ; and high-definition cameras to image the ocean colors and learn about their biological processes. (See a full listing of payload here.)

The researchers will also be able to sample parts of the atmosphere that they have not been able to reach or monitor for long durations--the upper troposphere and lower stratosphere. The aircraft can fly at an altitude of 19.812 kilometers and travel nearly 22,800 kilometers. That part of the atmosphere is "a crucial region that responds to and contributes to climate change at the surface, and we have come to realize that it is highly undersampled," says David Fahey, a research physicist at NOAA's Earth Science Research Lab in Boulder, CO. "If you don't know what is going on in certain regions of the atmosphere, you will misinterpret what is going on at the surface."

NASA and Northrop Grumman modified the aircraft to be a plug-in-play system, so that instruments can be easily taken off and new ones installed, depending on the mission. The plane can also be redesigned for a specific mission, if necessary.

"The planes are really robotic satellite-aircraft hybrids that are going to revolutionize the way we do science," Newman says. The next mission will be to study hurricanes in the Caribbean, and will include a new suite of instruments for the planes.

Copyright Technology Review 2010.