NASA is committed to measuring clouds on a global scale and will soon launch CloudSat, which will carry the first space borne cloud-profiling radar (CPR). Operating at 94 GHz, the CPR will conduct a 2 year global survey of cloud properties, collecting quantitative information on cloud-layer thickness, base and top altitudes, cloud optical thickness, and cloud water and ice contents. A follow-on mission is envisioned that will fly a low-mass cross-track scanning antenna. This will provide future missions with much improved spatial coverage for comparison with numeric models and reduced time between subsequent measurements over the same region. This proposed Phase I effort will investigate the required innovations to design and build a novel airborne prototype W-band (94 GHz) cross-track scanning antenna and wideband radar system. The proposed antenna will utilize a low-mass offset reflector and a frequency-scanned line-feed to achieve for the first time at W-band a cross track scan width of approximately 60 degrees. This design will lead to a prototype scanning radar system that can be flown on high-altitude platforms such as the NASA ER-2, WB-57 and Proteus. The prototype antenna will be compatible with existing space-qualified transmitters and can be scaled for space flight.