An evolution of the miniCTD and rapidSV, the rapidCTD has been designed to deliver the highest quality CTD casts at rapid drop rates. An evolution of the miniCTD and rapidSV, the rapidCTD is designed to operate autonomously and optionally in conjunction with the Teledyne OceanScience rapidCAST underway profiling winch to deliver the highest quality CTD casts, while the vessel is underway. A conductivity cell designed for optimum flow-through, a fast response thermistor sensor and a 0.01% pressure sensor synchronously sampling at up to 32Hz deliver the highest quality profiles in a robust package