Abstract: The Signals of Opportunity Airborne Demonstrator (SoOp-AD) was developed as part of the NASA InstrumentIncubator Program (IIP) with the goal of maturing the use of SoOp from existing communication satellites in geostationaryorbit, operating within the heavily used P-band (under 500 MHz) spectrum for soil moisture observations. P-band offers the benefit of roughly five (5) times deeper soil penetration compared to conventional L-band methods. SoOp-AD operates in a bi-static radar configuration…