Soil Moisture Satellite

Soil Moisture Satellite

On Friday, January 30th after 2 failed attempts NASA’s Soil Moisture Active Passive Satellite (SMAP) was finally launched on a Delta 2 rocket. The SMAP have been in development for almost 2 decades, once it is in orbit at 426 miles above the Earth’s surface it will measure soil moisture content. This data is critical to understand and monitor the changes in the Earth’s hydrological cycles. The satellite will also track soils in the Northern Hemisphere and evaluate which areas are absorbing and sequestering the most carbon.

Measurements of water will be made from the topsoil, the first 2 inches, of soil on the surface. Topsoil is where our food and other vegetation grows making soil moisture vital, of course soil moisture levels indirectly affects our lives in a multitude of other ways as well. And SMAP will also be able to tell where the earth is frozen, thawed or thawing.

The Soil Moisture Active Passive satellite will measure moisture in the Earth's topsoil for 3 years and produce global maps.

The Soil Moisture Active Passive satellite will measure moisture in the Earth’s topsoil for 3 years and produce global maps.

Measurements will be made every 2 to 3 days for a minimum of 3 years. This methodology allows for global changes to be tracked over a larger time-scale, accounting for large storms as well as seasonal variation. SMAP will measure all area not covered in water, where not frozen the amount of water found between the minerals, rocky material, and organic particles found in soil will be measured. Liquid water at the top layer can be quantified, but ice cannot.

The soil moisture satellite will aggregate data collected into global maps. The maps can be used by scientists to better understand water and carbon cycling on a grander scale. Hydrological cycling is a bit more complex than what we are taught in grade school with the continuous cycling through the steps of evaporation from the oceans and land to condensation forming clouds that then drop rain or snow on the ground (precipitation), followed by the water flowing across the land before returning to the sea. For example, that simplistic cycle doesn’t account for the water plants transpire. Evaporation rates from land surfaces are dependent on the level of soil moisture.

However, even more complicated is the carbon cycle, it has several more branches than the water cycle. Carbon cycles among the planet’s atmosphere (air), pedosphere (soil), lithosphere (rock), hydrosphere (surface water: ocean, lakes, and rivers), and the cryosphere (all forms and places where ice is found on Earth including sea ice, snow, glaciers, and permafrost). An example that helps make this less abstract is the carbon found in air, dissolves into water is emitted from underground sources as well as all breathing organisms.

Weather and climate change studies will benefit from the influx of large scale data the satellite will collect. Soil moisture data is key in gaining a deeper understanding of water flows, heat and energy transfer between the Earth’s surface and the atmosphere and how those elements affect the global weather and climate. Little is currently known about soil moisture and its variability, especially on a global scale. Measurements from SMAP will aid in developing more predictable and reliable weather predictions and climate models.

To learn more about NASA’s Soil Moisture Active Passive satellite, its mission and news visit: