Measuring Soil Moisture, from Outer Space

The headlines in space news are all about Mars these days, but NASA is doing some seriously cool science here on Earth too. This last January NASA launched SMAP, a satellite designed to measure soil moisture from orbit.


Courtesy of NASA

How does it measure soil moisture from orbit? SMAP orbits at more than 400 miles above the Earth, which is quite a distance to be measuring soil moisture, much less anything else. The satellite produces a radio wave, bounces the wave off the surface of the earth, and listens to the returning radio wave. Somehow (and this is above my pay-grade) that information is used to determine the moisture content in the top 2 inches of soil, as well as determine if the soil is frozen or thawed.

And SMAP is fast. The signal takes microseconds to bounces off the ground, the satellite orbits the Earth every 98 and a half minutes, and it maps the whole Earth in under 3 days. To make up for its small field of measurement, the whole satellite spins at almost 15 revolutions a minute, effectively measuring 1000 km consecutive “loops” on the surface of the earth. That’s a 1000 km “loop” every 4 seconds. (If your head is spinning, watch the video again, and appreciate that they slowed it way down).

Why is all of this so important? Beyond being super cool (my Star Trek dreams are coming true!) this data will be incredibly important to the advancement of the sciences and our understanding and stewardship of Earth. SMAP will give researchers, policy makers, and resource managers the ability to monitor drought conditions, predict flooding events, assist crop productivity, and forecast weather with greater fidelity. More importantly, SMAP will give us greater insight into the water cycle, the carbon cycle, and the energy cycle, which are all interlinked and fundamental to the health of Earth’s biosphere.

Check out more on the project at SMAP.

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