A Metamaterials-Based Spaceborne Multi-function Ka-Band Radar for Ocean Surface Vector Wind Scatterometry, Sea Surface Altimetry, and Precipitation Profiling

Ocean surface vector wind and significant wave height measurements with global coverage are needed as a primary data source for maritime hazard warnings, assimilation in global and regional numerical weather prediction (NWP) and ocean wave models, and tropical cyclone forecasting and storm surge warnings. While in-situ sensors (e.g., buoys) can provide direct measurements of the wave spectrum and either direct or inferred estimates of near surface winds, it is infeasible to disperse them throughout the global oceans with the requisite coverage density. For these reasons, it has long been recognized that space-based environmental monitoring (SBEM) platforms are the most effective approach to closing key spatiotemporal measurement gaps, with the first dedicated wind scatterometer mission dating back almost fifty years. While there has been a consistent presence of ocean surface wind sensing radar and radiometer payloads in orbit in the years since, the multi-satellite observing system has persistently lacked the coverage and revisit rate necessary to close relevant gaps for data assimilation in models and the measurement quality needed in high priority regions such as near the coast and in polar regions with sea ice.ÝThe proposed effort centers around the modification of proven metamaterials-based, spaceborne radar technology to enable a novel Ka-band, electronically scannable, pencil-beam radar payload for a SmallSat-class spacecraft. The instrument will provide wide-swath, high-resolution ocean surface vector wind (OSVW) and significant wave height (SWH) observations in addition to vertical profiles of precipitation rateÝandÝDoppler-based horizontal wind vectors within precipitating volumes. Navy operations rely greatly on accurate and timely measurements of ocean waves and winds to support littoral operations, amphibious missions, and special operations air and sea deployments. Satellite-based OSVW and SWH measurements from the proposed Ka-band system would significantly improve operational effectiveness and safety for these activities, especially when combined with forecasting tools and other terrestrial and airborne sensors. In the Phase I Base effort, the Agile Radar team will execute an observing system simulation study to assess OSVW, SWH, and precipitation rate and Doppler sensitivity to inform the driving system design, optimize radar sampling parameters, and assess measurement coverage and quality. In parallel, our team will modify existing antenna designs at other frequencies to demonstrate feasibility of the enabling Ka-band metamaterials antenna tile. Additionally, the Phase I Option entails scoping of an airborne demonstration instrument, which would constitute the Phase II effort, and arriving at a preliminary hardware and software design.