A new deep ocean capable profiling vehicle was developed at WHOI during 2002-2003. It was modeled after the High Resolution Profiler, a robust data acquisition system for studying mixing in the deep ocean. A test cruise was planned for November 2003, but foul weather delayed it until January 2004.
To minimize vibrations that would contaminate the data collected, the new instrument is a free vehicle, like its predecessor. The vehicle uses ballast weights to descend, which are jettisoned when one of the dive termination criteria is met, then excess buoyancy in the body allows rapid ascent to the surface where it is recovered.
The new vehicle uses contemporary components and hardware, enhancing maintainability for the coming years. The sensor systems selected are highly accurate, and sample at precisely timed intervals. Each fulfills a task of describing a scale of ocean temperature, conductivity or velocity. Instrument configuration is flexible and extensible, so when newer and better sensors become available, they may be employed on the profiler. All the data is logged to memory during the dive and downloaded to a shipboard computer after recovery.
Since the HRP-II controls its own operation, several levels of redundancy in terminating each profile were incorporated. First, as soon as any of the dive termination criteria is met, the weights are released. For additional robustness, a second computer monitors the main computer to assure its operational status, and can also release the weights independently. A low power condition triggers weight release if the voltage is below a threshold. In addition to these logical methods of dive termination, several mechanical back-ups are employed. Several sizes of shear pins can be used in the releases, and corrodible bolts are part of the system.
The ultimate back up system, newly implemented in this profiler, is a mud extractor. The pressure data is monitored, and if no change is detected in one minute, a 1.5 meter long plastic rod will be slowly pushed out of its housing, ideally separating the profiler from the bottom.
The completion of the new instrument with all the enhancements, and successful operation on the test cruse was a great accomplishment. Now we look forward to using it in studies of deep ocean mixing during the years to come.
keep development costs low, we decided to use proven, off the shelf
components and sub-systems when possible. The
maintenance of the system was simplified as a result of using parts
already used by others in the oceanographic community.
The main exception was the CTD. One
that fit our specifications did not exist, so a new design was
developed for this application.
The enhancements to the system (shown during dock tests) are the following:
the on-board controller was based on a 386 PC104 CPU with:
The talent of the engineers involved in
development effort contributed greatly to its success. Their
expertise, commitment and sense of humor made the process go smoothly.
The "team" and their
areas of responsibility are listed below:
Ken Doherty + Mechanical Gurus: responsible for body design, materials selection,
Terry Hammar battery specification, mechanical systems, EF collar, assembly.
Megan Carrol Designed and fabricated chassis.
Ed Hobart PC/software Guru: selected, configured, formatted CPU and add-ons.
Developed logger software, connectivity protocols & GUI interface.
Ellyn Montgomery Project manager. Worked on WD/PC board software, internal
communications, integration, component and system testing.
Bob Petitt Electronics Guru: responsible for CTD design and fabrication, design
assembly of WD/Power control boards and filter boards, electronics
Robin Singer Developed CTD controller software.
Fred Thwaites + Designed and built custom ACM transducer sting and the transducer
Craig Marquette elements, ACM testing.
The HRP-II is a complex system, comprised of many
elements as diagramed in the schematic of the system at the
right. Components with grey background are either in the HRP
pressure case or on the instrument body. The PC with the white
background is the one the stays on the ship and is used to communicate
withe the HRP-II via a network connection to evaluate sensor function,
set up a dive or offload data. The contrtoller is in the large
boxes on the left, the sensors are shown on the right, and the data
connectivity is indicated by the lines in the middle. The red
lines indicate power connections.
The configuration shown was used successfully on a test cruise in January 2004. In this case, data was acquired simultaneously from five sensors that output serial data and ten sensors that produce analog signals. The data was acquired and logged to memory during the downcast, then copied to files on disk after the weights were jettisoned at the end of the profile.
(All the links to the subsystem descriptions below
can also be reached from the main HRP-II page (use the Browser's back
button to return here).)
Power to the computer (PC104 CPU) and the "watchdog" is always on. In general, the autonomous operation of HRP-II is coordinated by logger software running on the dive control computer. However, the autonomous watchdog (a specialized power control card) can take over if the logger appears to have failed.
the logger, watchdog and power control boards allow configured sensors to be turned on and off
under software control. During a dive, data collected by
the CTD and altimeter is monitored by the logger and watchdog as it is
broadcast on the internal network.