SAN FRANCISCO — After a decade in orbit, NASA’s QuikScat satellite has stopped capturing highly detailed data on ocean winds, a loss that is particularly troubling to scientists and meteorologists because the United States government has no plans for a near-term successor.
The QuikScat scatterometer stopped working Nov. 23 when the bearings in the spinning antenna’s motor wore out. For months, mission officials had been expecting the scatterometer’s demise due to increased friction in the bearings. The mechanism that made the antenna rotate was designed to operate for five years, not 10 years, said Robert Gaston, QuikScat project manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
Nevertheless, no near-term successor has been identified. “There are a number of studies, mostly headed by the National Oceanic and Atmospheric Administration [NOAA] and strongly supported by NASA, looking at various options for replacing that capability,” said Michael Freilich, Earth Science Division director at NASA headquarters in Washington. “No decision has been made.”
QuikScat, built by Ball Aerospace & Technologies Corp. of Boulder, Colo., provided nearly instantaneous data on wind speed and direction over 90 percent of the world’s oceans. It was a valuable source of information for oceanography, meteorology and climate studies, government officials said.
“From a scientific standpoint, the loss of QuikScat will definitely be felt,” Freilich said. “Even though other countries have launched similar missions, QuikScat was contributing immensely with its coverage, accuracy and spatial resolution of winds over the ocean.”
To revive that capability, NOAA and NASA officials may launch a U.S.-built scatterometer on the Japan Aerospace Exploration Agency’s Global Change Observation Mission (GCOM)-W2 satellite scheduled for launch in early 2016, Freilich said. The proposal has attracted serious consideration because it would be far less expensive than developing a new U.S. spacecraft, said Andy Gerber, manager of civil and commercial space programs at the Jet Propulsion Laboratory.
In addition, Japan has a history of carrying U.S. scatterometers into space. In 1996, the NASA Scatterometer flew on Japan’s Advanced Earth Observation Satellite (ADEOS), and in 2002, the NASA SeaWinds scatterometer was carried into space on ADEOS-2. Both spacecraft suffered mission-ending power failures during their first year on orbit. “Flying scatterometers in association with Japan is not new to us,” Freilich said.
Still, any new program will require funding, and there is no money set aside in the NASA or NOAA budgets for a QuikScat follow-on, government officials said. “Congress has to act now,” Gerber said.
Rep. Ron Klein (D-Fla.) introduced legislation in September, the Hurricane Satellite Modernization Act, to authorize construction of two new satellites with advanced instruments capable of monitoring winds over 90 percent of the world’s oceans.
Until a new satellite or scatterometer is launched, U.S. scientists and government officials will rely on data derived from the Advanced Scatterometer, built by Germany’s Dornier Satellitensysteme GmbH, flying on the Metop-A satellite launched in 2006 by the European Space Agency and the European Organization for the Exploitation of Meteorological Satellites. In addition, NASA and NOAA signed a letter of intent in mid-November with Indian officials to share data derived from the Scanning Scatterometer, developed by the Indian Space Research Organisation’s Space Applications Center and launched in September aboard India’s OceanSat-2. “We are working hard to ensure rapid data exchange,” Freilich said.
While the demise of QuikScat will result in the loss of useful information on the location, structure and intensity of distant storms, it will have little or no impact on forecasting hurricanes headed for the United States, said Dennis Feltgen, spokesman for the National Weather Service’s National Hurricane Center in Miami. This topic was particularly controversial in 2007, when Bill Proenza, the National Hurricane Center’s director, was ousted from his post after declaring that the loss of QuikScat would harm hurricane forecasting.
Storms destined for the United States are tracked by aircraft, land-based Doppler radar, ocean buoys and two NOAA Geostationary Operational Environmental Satellites, Feltgen said. “We would like to have QuikScat continue, it’s been great,” he said. “But the quality of hurricane forecasting won’t suffer.”
Because QuikScat’s antenna no longer rotates, the spacecraft cannot collect information on surface winds over an 1,800-kilometer swath of land, ocean and ice as it has daily for 10 years. Still, the QuikScat scatterometer continues to function, providing useful remote sensing data over specific regions and giving scientists a way to test the accuracy of other space-based scatterometers.
“We can compare QuikScat data with data from other satellites and determine the bias between the two,” Gaston said. “As long as we can do useful work with the satellite in this configuration, we expect to operate it.” The QuikScat program costs approximately $3.5 million a year to operate, he added.
The National Research Council’s Earth science decadal survey calls for a much more robust capability as part of the Extended Ocean Vector Wind Mission. That mission, which would include two scatterometers designed to offer greater resolution and to minimize the impact of rain on data retrieval, should be launched between 2013 and 2016, according to the report, “Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond,” released in 2007. The National Research Council estimates that the Extended Ocean Vector Wind Mission would cost $350 million.