The technical objectives for the proposed Phase I study are: 1.Develop a compact, dual-wavelength antenna system capable of electronically scanning or producing multi-beams at different incidence angles, conical scanning and generating matched beams at both wavelengths. 2.Determine the optimal frequencies for the dual-wavelength operation that balances resolution, sensitivity, atmospheric attenuation, sea clutter contamination, size and weight. This will include conducting a brief literature review to select a model or develop a model for simulating the radar response to precipitation as a function of frequency and for a range of precipitation rates. Simulation will likely be based on Mie/Rayleigh scattering and attenuation models using a Gamma drop-size distribution shape. 3.Develop a compact, power efficient dual-frequency transceiver design that is based on surface mount RF components and low-noise monolithic microwave integrated circuits (MMICs) receivers. While custom MMICSs are available from several vendors, RSS and UMass will develop the low frequency RF and digital circuit board designs. 4.Investigate and develop compact, low-voltage power amplifier designs to produce high average power linear transmit signals. Design will need to operate unpressurized at the high altitudes typical of the Global Hawk UAV and similar aircraft. 5.Develop advance remote sensing algorithms to interpret the unique sampled data from the proposed instrument and retrieve high resolution maps the ABL winds, precipitation and ocean surface winds within tropical cyclones.