SAN FRANCISCO — NASA is marshalling airborne and space-based remote sensing instruments to gather data on the Gulf of Mexico oil spill that began with the April 20 explosion of an offshore drilling rig leased by BP. The space agency is tracking the location of the slick and trying to determine the areas where the greatest concentration of oil poses a serious threat to coastal habitats.
Initially, NASA obtained images of the widening oil spill from the Moderate Resolution Imaging Spectroradiometer (MODIS) flying aboard NASA’s Terra and Aqua Earth observing satellites. MODIS remains the primary instrument being used to observe the extent of the oil slick, said Michael Goodman, program manager for natural disasters within the NASA Earth Sciences Division’s Applied Sciences Program. Both the frequency of the MODIS observations, which occur approximately twice a day, and the fact that MODIS covers a 2,300-kilometer-wide swath makes it an important tool for tracking the location and extent of the oil slick, he added.
More detailed data are being drawn from Terra’s Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). While MODIS provides imagery with a resolution of 250 square meters per pixel, ASTER offers between 15 and 90 square meters per pixel. That higher resolution is helping scientists find the edges of the oil slick, Goodman said.
NASA officials also are working with other federal agencies to provide data on the varying concentrations of oil in the sea. For that job, NASA is conducting flights of the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), an instrument that gathers data in 224 spectral bands, on a Lockheed ER-2, the civilian version of the U.S. Air Force U-2 reconnaissance plane.
Following Hurricane Katrina, Gregg Swayze of the U.S. Geological Survey’s Spectroscopy Lab in Denver developed a technique for using AVIRIS data to identify areas where crude oil produces a thin film on the water as well as areas where high concentrations of crude oil mix with water. “That’s the oil the first responders want to identify so they can send boats and skimmers to interdict it,” Goodman said. “By combining the different spectral channels, we think we can identify those areas of thick oil, the emulsified oil, versus the sheen.”
In response to a request by the National Oceanographic and Atmospheric Administration (NOAA), NASA gathered AVIRIS data over the Gulf oil spill on May 6 and May 10. “This is still experimental work, but we are hopeful that it will produce some images of the oil concentration,” Goodman said. During this oil-monitoring effort, which may continue for another one to two weeks, the AVIRIS instrument team has relocated temporarily from NASA’s Jet Propulsion Laboratory in Pasadena, Calif., to the Johnson Space Center in Houston. The ER-2, which typically takes off from NASA’s Dryden Flight Research Center in Edwards, Calif., has been sent to Ellington Field in Houston, Goodman said. NASA’s AVIRIS team will produce initial data files while more-detailed analyses will be performed by Swayze and his U.S. Geological Survey colleague Roger Clark, Goodman said.
AVIRIS data also will be used to gauge the health of plants along the Gulf Coast. “It’s possible to detect signs of stress in vegetation using those spectral signatures,” said Diane Wickland, a terrestrial ecology program scientist at NASA headquarters. “Plants have pigments that absorb light in the visible region. When they are stressed, their absorptions are less and you can see a change in their color.”
In another effort to investigate the concentration of oil in the water, NASA is studying the effectiveness of the remote sensing instrument on the U.S.-French Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and the High Spectral Resolution Lidar on NASA Langley Research Center’s King Air B200 aircraft. “Data from both the space-based and airborne lidars will be used to investigate the thickness of the oil spill below the surface of the water and evaluate the impacts of dispersants spread on the spill to break up the oil,” Goodman said. He cautioned, however, that the results of the lidar studies would be used in research but would not be delivered to emergency response teams because the technique was experimental and had not been validated or verified.
NASA’s efforts to provide information on the oil spill and its impact is one element of NOAA’s oil-monitoring campaign. In addition, NOAA is gathering data from synthetic aperture radars carried by its own geostationary and polar-orbiting weather satellites as well as those deployed by commercial and government partners around the world, including Japan’s Advanced Land Observing Satellite, France’s Spot 5 satellite, Canada’s Radarsat-1 and Radarsat-2 satellites, the European Space Agency’s Envisat and Infoterra of Germany’s TerraSAR-X satellite, according to NOAA spokesman John Leslie.
