In Indiana, Purdue University researchers developed a technology that can more accurately sense soil moisture below the surface by measuring the reflections of communication satellite signals. The technology makes use of a specialized receiver to capture reflections of communication satellite signals having wavelengths of about one meter, which scientists refer to as P-band.
Conventional satellite technology used for measuring soil moisture cannot operate at these longer wavelengths due to the required antenna size and the substantial interference from communications links. Current observations of soil moisture from a satellite uses wavelengths of about 20 centimeters and can only penetrate the soil about 2 inches.
The new technique is known as “signals of opportunity,” or SoOp, and utilizes the same transmissions that are the source of interference that prevents measurements from other methods. P-band is expected to be sensitivity to soil moisture down to about 6 to 8 inches below the surface.