SMAP!!!

In an effort to better understand our planet and it’s resources, NASA has developed a fleet of satellites to scan and analyze the earth’s surface and atmosphere. In 2002, a new Earth System Science Pathfinder, or ESSP, was proposed to analyze soil moisture and annual freezes and thaws; this ESSP was called Hydros. Initially approved for formulation phase in 2003, Hydros was set to be completed and launched by NASA’s JPL in 2010. However, due to a lack of funding, the project was discontinued in 2005. Still being on the top of the recommended projects list, Hydros was to be redeveloped in  2008 under the acronym SMAP (Soil Moisture Active Passive).

SMAP, set to launch in Fall 2013, will be able to measure the top two centimeters of soil moisture around the earth in 3 days. This information is incredibly beneficial to geologists, biologists, farmers, and the general population around the world. Meteorologist will be able to utilize the data to better predict weather and climate changes, as well as the threats of flood and draught. Links between terrestrial water, energy, and carbon cycles will be easier to observe for scientists. The fluctuations in these cycles are important to understanding atmospheric changes, especially in boreal landscapes, some of the most important carbon reducing areas on earth. Before SMAP, analyzing soil moisture was done by hand, sticking a meter into the ground and getting individual readings foot by foot. To map the entire globe would take years, but SMAP is able to do it in three days, sharing it’s information with anyone who seeks it. 

SMAP combines two different tools to measure soil moisture, maximizing its accuracy and clarity. The active component of SMAP is a rotating radar which bounces a 1.2 gigahertz signal off of earth’s surface, maximizing resolution at 3 km but lacking accuracy. To compensate for the radar’s lack of accuracy, SMAP has a passive radiometer which measures the radiation from earth’s surface on a 1.41 gigahertz wavelength. However, the accuracy maximizes at 40 km. An algorithm combines the data from the two sensors to maximize the efficiency and accuracy of the satellite.

In order to get SMAP into space, the instruments team, led by Wendy Edelstein, had to be innovative with their design. They had to create a rotating radar antenna large enough to transmit the signal down to earth and receive it back in space, but small enough to fit in the second stage compartment of an Atlas model launch vehicle. To accomplish this, the instruments team created a conical scanning mesh reflector that deploys in space. It is connected to a spin platform assembly by a folding mechanical arm. Once SMAP is in orbit, the arm unfolds, the mesh is unfolded, and the spin platform assembly begins to rotate. Thus begins the journey of SMAP.