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NASA Mission Generates Global Maps Measuring Soil Moisture

PIA18057_modestNASA’s Soil Moisture Active Passive (SMAP) observatory has generated its first global maps.

SMAP launched on Jan. 31 of this year, with the goal of a three-year mission to map global soil moisture and detect whether the soil is frozen or thawed. The information gathered will help scientists understand a gamut of natural processes, from the relations between Earth’s water, energy, and carbon cycles to the drastic changes in weather and climate.

A key figure in SMAP’s mission is a 20-PIA18058_modestfoot-wide antenna that spins at the speed of 14.6 revolutions per minute. The antenna takes cone-shaped scans all across the Earth’s surface, which allows SMAP to map out the entire globe from high-resolution data.

SMAP also uses a radar and radiometer that transmit microwave pulses and analyze the signals that bounce back in order to determine the amount of water. The radar and radiometer sensors capitalize on each other’s strengths to work around any weaknesses, with the radar able to measure soil moisture with the low spatial resolution of 1.9 miles, while the radiometer measures soil moisture with a higher spatial resolution of 25 miles but with less accuracy.

Weak signs that indicated little water were presented in blue colors, while strong signs that indicated the significant presence of water were presented in red. Strong dry areas included the Sahara and Gobi Deserts, while wet areas included the Amazon and Congo rain forests. In America, the Rockies, Sierra Nevada and Cascade mountain ranges and land in east of the Mississippi River tended to have strong radar echoes that indicated high levels of soil moisture. The Great Plains area and other grasslands had relatively weak radar echoes indicating low levels of soil moisture. Areas with low soil moisture tended to have high temperatures, whereas areas with high soil moisture had low temperatures.

SMAP also collected radar data over ocean and sea ice, which allows them to measure surface wind conditions.

SMAP has every reason to be optimistic, as it has only recently began conducting synthetic aperture radar (SAR) processing, a way of producing radar measurements with certain spatial resolutions to use for routine science operations over land and ocean surfaces. SMAP expects more data in the future from the use of SAR, which means the capability to produce even more global maps.