Wave Characterization for Tomorrow's Oceans

Knowledge of the seas is essential to safe ocean navigation and offshore operations. Providing this environmental situational awareness to an unmanned surface vessel (USV) is a particular challenge. An automated information system and sensor that provides detailed wave information in real-time will vastly improve survival and enhance seakeeping performance, significantly increasing the probability of mission success. FutureWaves is a wave and vessel motion forecasting system that includes a specialized wave-sensing Doppler radar, coherent (amplitude and phase) wave nowcast model, and platform-specific motion forecasting. The system determines height, direction and timing of waves, and can provide critical wave information used to predict detailed vessel motions before they occur. It has been employed on numerous vessels from small Unmanned Surface Vessels (USVs) of 50'L to very large 950'L supply ships (e.g. LMSR), including a deployment on a 136,000 GT semi-submersible construction vessel, the SSCV THIALF. The system was recently integrated into the U.S. Navy Large USV (LUSV) prototype demonstrations aboard USNS APALACHICOLA (EPF-13) where it provided the autonomy system with dynamic evaluation of the Safe Operating Envelope using real-time wave measurement. FutureWaves system output includes key wave parameters: significant wave height and sea state, dominant wave period and direction, wave energy spectrum and directional spectrum. The system provides best course and speed for particular operations, and also makes deterministic predictions of vessel motions 1–2 minutes into the future, allowing for immediate decisions and actions during critical evolutions based on actual environmental measurements. The key component to achieve this is a specialized marine X-Band (9.3-9.5GHz) Doppler radar that measures the ocean surface orbital radial-velocities through Bragg backscattering in a 360° area around the vessel out to ~5km. The radar employs vertical polarization of the antenna in transmit and receive in order to substantially improve ocean surface measurements as compared to horizontal polarization of typical marine X-Band navigation radars. Custom signal processing of the ocean surface Doppler return yields real-time wave characterization in the form of a self-calibrating energy power spectrum, wave heights, direction, period, and trends of the ocean environment. It has been proven to operate with a wave height accuracy of 0.lm in up to sea state 6. The standard FutureWaves system is configured for the specific vessel installation, and has also been tailored with customized processing for specialized applications. NASA routinely deploys a portable version of the system which is approved for use on board US Navy LPD class ships as part of the Orion space capsule recovery for the Artemis Program. The LPD (Landing Platform Dock) is an amphibious warship that embarks, transports, and lands forces for expeditionary warfare missions primarily using landing craft and transport helicopters. LPD capabilities make it ideally suited for Artemis with the capsule being recovered into the well deck at the stern of the LPD, however controlling the well deck wave environment has been a challenge for the operation. FutureWaves was adapted to solve for the wave action inside the well deck, along with the associated crew module motions. The system provides the recovery ship with course and speed recommendations to minimize the well deck wave motion, thus improving safety of the crew module during this critical final step of the Artemis mission. As the Navy moves toward increased use of unmanned craft, including such multi-body recovery operations, an automated wave sensing and guidance system will be critical to mission success. This paper highlights some of the FutureWaves applications and validates performance with recorded data and verification of the system through sea tests. We review recent success in autonomous vehicle applications of the technology, and suggest a path forward for providing detailed ocean wave environmental awareness to autonomous vessels.