Low-Cost Aircraft Navigation System to Aid Global Climate Change Studies
--Douglas Isbell, NASA Headquarters, Washington, D.C. (Phone: 202/358-1753)
--Keith Koehler, NASA Wallops Flight Facility, Wallops Island, VA (Phone: 804/824-1579)
Information excerpted from NASA Press Release 96-99.
A low-cost aircraft navigational system developed by NASA is making it possible for scientists to make precise maps of ice sheets that should yield valuable data on the potential effects of global climate change. The system, which uses a personal computer to provide navigational data to the cockpit, allows aircraft pilots to fly flight paths to an accuracy of one foot. This allows the scientists on board the aircraft to map the icy terrain below to an accuracy of 4 inches.
NASA and university researchers today began their sixth mission since 1991 to map the ice sheets of Greenland. These missions are providing researchers with a baseline set of measurements to help them better understand glacial changes that may be due to global climate change.
The new navigation system that is aiding these researchers took less than six months to develop, according to Wayne Wright, system developer at the NASA Goddard Space Flight Center's Wallops Flight Facility, Wallops Island, VA. The system currently uses an IBM-compatible 486 personal computer, but it can be installed in an aircraft using a lap-top computer. "The total cost of the system is less than $3,000," Wright said.
A receiver in the aircraft tuned to the Global Positioning System of orbiting satellites acquires precise position information and then compares these readings to a predetermined flight path. The navigation system then generates steering signals that are sent to the autopilot to direct the aircraft toward its optimal path.
In addition, the system presents an aircraft position display to the pilot. This display allows the pilot to determine if the aircraft is right or left of the flight path centerline to within one foot. The system also can show the pilot position data on a larger scale, or the "big picture," such as the entire flight path. "The system can be used on other aircraft-based Earth science missions to map varied terrain such as volcanoes and coastlines," Wright said.
NASA pilot Rich Rogers compares using the navigational system to interacting with an aircraft piloting video game. "Flying science `lines' requires great precision, and is both challenging and fun at the same time," Rogers said. "Close coordination between the pilots, the aircraft flight crew, and science team is needed to successfully operate the navigation system and accomplish the Greenland mission," he added.
NASA ice mapping project scientist Bill Krabill calls the system "absolutely critical to be able to refly flight lines with a tolerance of 150 feet," which is the scientific requirement. "It is the only means by which this project can be properly accomplished." "In fact, the navigational system allows the aircraft to be flown within approximately 20 feet of previously measured points on the ice sheets," Wright said. This enables the researchers to both gather accurate measurements at a single data point and to record any regional changes from previous flights.
The current mission will include mapping previous data points over Greenland and new data points over Iceland and Spitsbergen. Points on the northern coast of Greenland are of particular interest because other satellite data indicate there is a possible decrease in the ice sheet's elevation, Krabill said. It has been estimated that a 10-inch decrease in the average height of the central Greenland ice sheet would result in a 0.04 inch increase in sea level of the world's oceans.
During the mission, which runs from mid-May to mid-June, a P-3B aircraft from Wallops will carry four instruments for mapping the ice sheets. The instruments include a laser ranging system from Wallops called the Airborne Topographic Mapper I (ATM I), a profiling laser system from Goddard, and an ice-penetrating radar from the University of Kansas in Lawrence. The fourth instrument, still under development, is a smaller version of ATM I. The 400-pound ATM II is approximately half the size of the ATM I.
Researchers located on the ice in Greenland will conduct ground truth studies beneath the flight path of the aircraft to verify the airborne data. The field team includes researchers from Ohio State University in Columbus, the University of Arizona in Tucson, and the University of Nebraska in Lincoln. The ice mapping program is conducted by Wallops for NASA's Office of Mission to Planet Earth, Washington, DC.
[Table of Contents]
[Previous]
[Next]