NEW YORK: A NASA satellite lifted off on Saturday with the hope it will transmit data that will help the world do a better job of preparing for floods and droughts.
The liftoff from Vandenberg Air Force Base in Southern California was the third attempt to launch the craft. Upper-level wind shear above the base near Lompoc had already prompted NASA to push Thursday morning’s launch to Friday.
The second postponement came after inspections revealed problems with the booster insulation of the United Launch Alliance Delta II rocket, according to the agency.
Once fully deployed, the 2,000-pound (907 kg) craft will aim two microwave-emitting instruments at the Earth’s surface and collect data that will enable the agency to determine the moisture content of the top two inches of soil planetwide and to calculate water depth to about three feet, said Jared Entin, NASA’s Washington-based project scientist for the Soil Moisture Active Passive, or SMAP, mission.
The radiometer and radar will work in tandem to pick up subtle changes in a narrow spectrum of microwave radiation known as the L-band, as the microwaves scatter and reflect from the Earth’s surface, said Entin.
“What we’re measuring is the dip in the energy coming back from Earth in this spectrum,” Entin said. “The more the dip, the more water is blocking the signal.”
The content of water in soil, and by extension in plants and crops, has been a somewhat opaque factor in forecast and climate models. Scientists have mainly relied on a relatively sparse array of ground instruments.
From an altitude of about 426 miles (686 km), the satellite will be able to sweep all of the Earth’s surface, regardless of cloud cover, in two to three days, offering a resolution of about five or six miles.
Scientists worked for several years to integrate the two instruments into a best-of-both-worlds view of the Earth’s surface. One detects a highly accurate signal but with much lower resolution, while the other can home in on smaller patches, but produce a much “noisier” signal, Entin said.
Although it will take more than a year to gather, calibrate, verify and analyse the information in a way that is suitable for scientific research, NASA plans to release early data sets within several months to forecasters and planners in such agencies as the United Nations World Food Program, U.S. Department of Agriculture and U.S. Centers for Disease Control and Prevention.
