NASA Eyes UAVs, Microsats for Measuring Soil Moisture

NASAscientists are studying the possibility of placing microwave sensors aboardunmanned aircraft and microsatellites as a way to obtain soil-moisturemeasurements at a bargain price.

NASA'sMarshall Space Flight Center in Huntsville, Ala., issued a notice May 16seeking potential ideas and sources for outfitting unmanned aerial vehicles(UAVs) and microsatellites with advanced L-band antennas for gatheringsoil-moisture measurements.

"Antenna design must be scaled to the properweight and size to be deployable from current UAVs with future follow-on workto embed the antenna into a microsatellite," NASA said in the solicitation.

Respondentsshould assume operating altitudes of 150-10,000 meters for UAVs and 700kilometers for microsatellites, and scale their sensors accordingly to meet theresolution requirements and other technical specifications, the notice said.

Climate andenvironmental scientists have long had an interest in soil-moisturemeasurements, which can aid in long-term weather forecasts and which also havepotential applications in agriculture and resource management, according toCharles Laymon, a research fellow at Marshall. "If we can increase the resolutionand frequency of observation, there's a wide breadth of other disciplines thatcould make use of this information," he said.

Up untilthis year, scientists interested in soil-moisture measurements were lookingforward to NASA's $175 million Hydros mission, which was funded as an alternateunder the agency's Earth Systems Science Pathfinder series of smallenvironmental-science satellites. But the agency axed Hydros at the beginningof the year due to a funding crunch affecting its science programs across theboard.

UAVs andmicrosatellites are now seen as promising low-cost alternatives for gatheringthe measurements.

"With therecent termination of the Hydros mission, we started looking at exploringwhether some of these platforms might serve as a technology bridge until thenext opportunity to re-propose the mission came along," Laymon said in aninterview.

Thechallenge, Laymon said, is to design L-band microwave sensors that are smallenough to fit on UAVs. NASA is still determining what size UAV would becompatible with this kind of experiment, according to NASA spokesman RickSmith. "There are some new technologies out there that are being developed wecan quickly harvest and modify slightly to serve our needs," he said. Marshallhas a history of using remote sensing techniques to obtain soil-moisture data,according to Steve Roy, a spokesman for the center. In recent years scientists have relied ondirect measurements combined with data collected by sensors aboard NASA's Aquasatellite, launched in May 2002, he said. But the data collected by Aqua is notparticularly effective for obtaining the information the scientists need, andthey hope that data collected on the UAVs will help scientists make betterlong-term weather forecast predictions, Smith said.

UAVs andmicrosatellites could significantly reduce the cost of gathering thesemeasurements, Laymon said.

"Thetraditional science platform that NASA builds for a science mission has a longlife of three to 10 years, incorporates a large number of instruments, andcosts hundreds of millions of dollars," Laymon said. "These technologies can dothings more cheaply. ... A UAV is a stepping stone in getting to amicrosatellite."

UAVs do notprovide the global, broad-area coverage of satellites. But they can be deployedrelatively quickly as dictated by weather conditions or other events and focusin on areas of particular interest, Laymon said.

Laymonexpressed hope that the responses to Marshall's request for information willlead to funding for technology demonstrations in the next two years or so. "The [request] is a first step in identifyingwho wants to play, and who has something to offer in the arena," Laymon said.

NASA'sGoddard Space Flight Center in Greenbelt, Md., working in conjunction with theagency's Wallops Flight Facility in Wallops Island, Va., already has had some success incorporatingmicrowave instruments on UAVs, according to Larry Hilliard, an engineer atGoddard and principle investigator forthe project.

Hilliardsaid the Goddard instrument is a simplified system, with the intention ofadding more capabilities to the instrument as the project proceeds. Scientistsencased the antenna in a type of foam structure that was of very low mass,allowing the UAV to handle the weight of the payload. The vehicle has not yetbeen flight tested, but could potentially be in the fall, Hilliard said.

Hilliard'steam is a potential collaborator for Marshall for the project outlined in therequest for information, Hilliard said.

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