HRP II—the development of a new vehicle for studying deep ocean mixing

The High Resolution Profiler II (HRP-II), a unique, autonomous untethered, deep-ocean capable, profiling vehicle was designed and developed at WHOI during 2002-2003. During a vertical profile, it measures and records temperature, conductivity, pressure, horizontal and vertical components of velocity and turbulent-scale temperature and velocity gradient data. Great care was taken to minimize vibrations that would contaminate data from the microstructure sensors; the vehicle's movement is driven by graity, the body materials and shape were optimized for stiffness and no computer disk activity is allowed while profiling. All sensors are positioned to measure the same volume of water, and allow undisturbed flow to reach each one. The HRP-II was tested over the continental slope in January 2004. All aspects of vehicle function were successfully tested during seven profiles, the deepest of which was to 1583m. On one dive to 835m, termination was achieved at 17m above the bottom, close to the design specification. Several sensor and controller issues were identified that need to be resolved, but overall the vehicle performance on the test cruise was exceptional. The vehicle design specification, mechanical and electrical systems, sensors, controller, communications protocols, and testing of the HRP-II are documented in this report.Funding was provided by the National Science Foundation under Grant No. OCE-0118401 and the G. Unger Vetlesen Foundation