SOIL. MOISTURE. ACTIVE. PASSIVE.

SOIL. MOISTURE. ACTIVE. PASSIVE. The one commonality between every speaker at NASA's Jet Propulsion Lab when discussing SMAP is that "they're not responsible for the name." Yes, SMAP, one of the dozens of acronyms NASA has for its missions, doesn't sound the most glamorous or exciting at first, but the National Research Councils Committee decided it was a top priority mission years ago. In 2008 SMAP evolved from NASA's Hydros (Hydrosphere State) mission which was selected as an Earth System Science Pathfinder mission in 2002, but was cancelled in 2005 due to budget constraints. More than a decade later, SMAP will finally launch in November of 2014. But what exactly do these four words mean?

SMAP is a spacecraft made up of a radiometer and a high-resolution radar that will measure the earth's soil moisture through active signal emission and remote sensing. The old fashion way of doing this was to physically go out into the desired area and measure the amount of soil moisture with a device that went only a few inches deep in one small hole. SMAP will create a more efficient way of not only measuring soil moisture across the entire world, but collecting data over time. The spacecraft can completely measure the entire surface of earth, up to 5 centimeters deep, in just three days. The data will not only be stored in science data archives at NASA,  but it will be available to other organizations interested in tracking weather and climate. SMAP has several benefits and applications in understanding our earth:

1. Predict the weather and understand climate
2. Predict droughts and floods
3. Determine the length of the growing season in boreal regions
4. Freeze/Thaw states
5. Vector born diseases

By predicting the weather as well as natural disasters such as droughts and floods, humanity has a better chance of preparing. Of course, it is impossible to control the weather, but for example, knowing days in advance that a giant hurricane is heading towards a major city, large amounts of people can evacuate before its too late and lives could be saved. (SMAP doesn't sound so boring anymore) In the boreal regions of North America and Russia, vast amounts of lands are covered by snow for a large portion of the year. Once the snow melts, life is restored to massive amounts of plants, which consume much of the carbon dioxide in the atmosphere, creating carbon sinks and affecting our ozone layer. SMAP will be able to determine if the growing season is growing or sinking.

SMAP is designed as a observatory, which is the body, and the instrument, which measures the data. It is made up of a radiometer and a radar. The radiometer is what measures with high accuracy, and the radar has a high resolution. The radar operates at L-band frequency (1.20-1.41 GHz) with a wavelength of 24 centimeters. With the antennae making one full revolution every four seconds, SMAP is able to section a swath of 1,000 kilometers wide of the earth's surface constantly and receive, compute, and store data on the craft. The spacecraft will function for three years and will be available in a data center.