Introduction HRP-II

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.

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Design Objectives

To 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:

• improved CTD, current meter, and compass sensor systems
• added an Electromagnetic Field sensor
• employed higher sampling rates
• implemented more accurate timing of the A/D data acquisition
• added a GPS receiver for surface position logging
• modified body size, shape and stiffness to push vibration peak > 30 Hz
• employed external battery packs
• implemented a bottom extractor
• developed a graphical user interface(GUI) for configuration and operation
• implemented a Watchdog computer to monitor logger operation
• increased data offload speed by employing current protocols
• employed contemporary computers of small form factor-   

   the on-board controller was based on a 386 PC104 CPU with:

• 16 Mb system memory
• 2 Gb memory for data
• disk to back-up data to after a profile
• 8 serial ports
• 1 parallel port
• an 10/100 baseT ethernet connection
• a 16 channel, 16 bit A/D converter
• Windows 2000

Along with the improvements, certain requirements remained the same for the new system.  It must:

• operate to  full ocean depth (6000 meters)
• be easy assemble and handle in low to moderate seas
• have sensors positioned to avoid flow disturbance and wake effects
• employ robust hardware and software and have failsafe mechanisms

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Engineering Support

The talent of the engineers involved in this 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.

Instrument Summary

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.

Internal communications between 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.

The body protects the electronics from the effects of working in the deep ocean, and was optimized for obtaining quiet measurements in profiles of up to 6000 meters.  The HRP-II is the only one in existance that is able to withstand the pressure of work in the deep ocean.

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