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.

"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.