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Artist's rendering of the SMAP instrument. Image credit: NASA

NASA to Launch SMAP Mission to Study Moisture, Predict Drought Accurately

NASA has announced the launch of its upcoming Soil Moisture Active Passive (SMAP) mission on January 29 from Vandenberg Air Force Base in California to provide accurate, highest-resolution global measurements of soil moisture ever obtained from space.

SMAP will launch from Vandenberg Air Force Base on a United Launch Alliance Delta II rocket and maneuver into a 426-mile (685-kilometer) altitude, near-polar orbit that repeats exactly every eight days. The mission is designed to operate at least three years.

For several months, California has been in a state of “exceptional drought.” The state’s usually verdant Central Valley produces one-sixth of the U.S.’s crops. Image Credit:  White House via Wikimedia Commons

For several months, California has been in a state of “exceptional drought.” The state’s usually verdant Central Valley produces one-sixth of the U.S.’s crops.
Image Credit: 
White House via Wikimedia Commons

The mission will also detect whether the ground is frozen or thawed and this data can be used to enhance scientists’ understanding of the processes that link Earth’s water, energy and carbon cycles.

In a briefing held by its scientists Christine Bonniksen, SMAP program executive with the Science Mission Directorate’s Earth Science Division at NASA Headquarters in Washington, Kent Kellogg, SMAP project manager with NASA’s Jet Propulsion Laboratory in Pasadena, California, Dara Entekhabi, SMAP science team lead, Massachusetts Institute of Technology, Cambridge, Massachusetts, and Brad Doorn, SMAP applications lead, Science Mission Directorate’s Applied Sciences Program at NASA Headquarters, the online social media Twitter was also used as a medium to interact with space fans and experts all over thw world.

SMAP is the last of five NASA Earth science missions scheduled for launch within a 12-month period. NASA monitors Earth’s vital signs from land, air and space with a fleet of satellites and ambitious airborne and ground-based observation campaigns.

Using an advanced radar and radiometer, the satellite will be able to peer beneath clouds, vegetation and other surface features to monitor water and energy fluxes, helping improve flood predictions and drought monitoring.

Data from the three-year mission will play a crucial role in understanding changes in water availability, food production and other societal impacts of climate change. The scientific instruments to be used in the mission include a radar and a radiometer.

A new NASA satellite that will peer into the topmost layer of Earth’s soils to measure the hidden waters that influence our weather and climate is in final preparations for a Jan. 29 dawn launch from California.

Artist's rendering of the SMAP instrument. Image credit: NASA

Artist’s rendering of the SMAP instrument. Image credit: NASA

The SMAP mission will study a key measure of our water planet, how freshwater cycles over Earth’s land surfaces in the form of soil moisture, produce the most accurate highest-resolution global maps ever obtained from space of the moisture present in the top 2 inches (5 centimeters) of Earth’s soils.

It will detect and map whether the ground is frozen or thawed, the data that can be used to enhance scientists’ understanding of the processes that link Earth’s water, energy and carbon cycles.

“With data from SMAP, scientists and decision makers around the world will be better equipped to understand how Earth works as a system and how soil moisture impacts a myriad of human activities, from floods and drought to weather and crop yield forecasts,” said Christine Bonniksen, SMAP program executive with the Science Mission Directorate’s Earth Science Division at NASA Headquarters in Washington.

Globally, the volume of soil moisture varies between three and five percent in desert and arid regions, to between 40 and 50 percent in saturated soils. In general, the amount depends on such factors as precipitation patterns, topography, vegetation cover and soil composition.

There are not enough sensors in the ground to map the variability in global soil moisture at the level of detail needed by scientists and decision makers. From space, SMAP will produce global maps with 6-mile (10-kilometer) resolution every two to three days.

Researchers want to measure soil moisture and its freeze/thaw state better for numerous reasons. Plants and crops draw water from the soil through their roots to grow. If soil moisture is inadequate, plants fail to grow, which over time can lead to reduced crop yields.

Moreover, energy from the sun evaporates moisture in the soil, thereby cooling surface temperatures and also increasing moisture in the atmosphere, allowing clouds and precipitation to form more readily. In this way, soil moisture has a significant effect on both short-term regional weather and longer-term global climate.

In summer, plants in Earth’s northern boreal regions — the forests found in Earth’s high northern latitudes — take in carbon dioxide from the air and use it to grow, but lay dormant during the winter freeze period. All other factors being equal, the longer the growing season, the more carbon plants take in and the more effective forests are in removing carbon dioxide from the air.

Artist's rendering of the SMAP instrument. Image credit: NASA

Artist’s rendering of the SMAP instrument. Image credit: NASA

Since the start of the growing season is marked by the thawing and refreezing of water in soils, mapping the freeze/thaw state of soils with SMAP will help scientists more accurately account for how much carbon plants are removing from the atmosphere each year. This information will lead to better estimates of the carbon budget in the atmosphere and, hence, better assessments of future global warming.

Dara Entekhabi, SMAP science team leader at the Massachusetts Institute of Technology in Cambridge, says: “Today’s computer models disagree on how the water cycle — precipitation, clouds, evaporation, runoff, soil water availability — will increase or decrease over time and in different regions as our world warms. SMAP’s higher-resolution soil moisture data will improve the models used to make daily weather and longer-term climate predictions.”

SMAP’s two advanced instruments work together to produce soil moisture maps. Its active radar works much like a flash camera, but instead of transmitting visible light, it transmits microwave pulses that pass through clouds and moderate vegetation cover to the ground and measures how much of that signal is reflected back.

Its passive radiometer operates like a natural-light camera, capturing emitted microwave radiation without transmitting a pulse. Unlike traditional cameras, however, SMAP’s images are in the microwave range of the electromagnetic spectrum, which is invisible to the naked eye. Microwave radiation is sensitive to how much moisture is contained in the soil.

The two instruments share a large, lightweight reflector antenna that will be unfurled in orbit like a blooming flower and then spin at about 14 revolutions per minute. The antenna will allow the instruments to collect data across a 621-mile (1,000-kilometer) swath, enabling global coverage every two to three days.

SMAP’s radiometer measurements extend and expand on soil moisture measurements currently made by the European Space Agency’s Soil Moisture Ocean Salinity (SMOS) mission, launched in 2009. With the addition of a radar instrument, SMAP’s soil moisture measurements will be able to distinguish finer features on the ground.

SMAP will be the fifth NASA Earth science mission to launch within a 12-month period.

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