Results Of The CODAR Offshore Remote-Sensing Project
M.W. Spillane, Randy D. Crissman, M. W. Evans, Donald E. Barrick, Belinda Lipa, B. Braennstrom · Offshore Technology Conference · 1986
ABSTRACT The CODAR high frequency (HF) radar has been adapted to provide operational, real time, offshore environmental monitoring and hazard warning information to production platform and drilling vessel operators. CODAR is capable of remotely sensing ocean surface currents, wave properties, over-water surface winds an ice movement without in-water instrumentation. An optional Doppler transponder developed for use with the system can be used to track the movements of ships, ice, or current drifters. The programs and projects undertaken in the last five years to adapt CODAR to offshore installations are reviewed in this paper. The objective is to give an overall view of the goals, the major obstacles, and solutions developed in the process. Although the original schedule for achieving an operational offshore system has not been met, the lessons learned during the numerous programs and projects are considered to be invaluable for future applications of the system. INTRODUCTION The HF Coastal Ocean Dynamics Applications Radar, CODAR, was developed by D. E. Barrick at the Wave Propagation Laboratory of the U. S. National Oceanic and Atmospheric Administration (NOAA) in Boulder, Colorado between 1974 and 1984. The primary emphasis during the development of the radar at NOAA was on measuring surface currents and wave properties from a coastal site. The adaptation of CODAR to offshore operations was initiated by Gulf Oil Corporation, now a subsidiary of Chevron Corporation, in 1982 (1). The involvement by Gulf in the adaptation of CODAR to offshore applications was made possible with the formation of Codar Technology, Inc. in 1980 and Codar Systems, Inc. in 1982 by NOAA personnel responsible for the radar's development. In 1984, NOAA eliminated its direct involvement in the development of CODAR. The adaptation of CODAR to offshore operations required both hardware and software modifications. The major obstacles identified at the initiation of the project were:*Development of a compact, lightweight crossed-loop antenna capable of operating at two frequencies and being easily installed on an offshore drilling derrick. Two radar frequencies are required to extract wave properties from sea states likely to be encountered offshore (25.4 Mhz for Hs 3.5 m).*Development of system control software to enable the system to acquire and process the radar signals in real-time.*Extension of the theoretical and mathematical techniques to transform backscattered radar signals into useful environmental data at an offshore location.*Development of methods and algorithms for removing the motion of a floating vessel from the radar signal to eliminate biases in the measured parameters. The development of these capabilities required the deployment of a GODAR system on a Gulf of Mexico fixed production platform and a semisubmersible drilling vessel in the North Sea. During the installation and operation of CODAR from these offshore locations, several operationally significant difficulties were encountered and resolved.