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Thetis Profiler

The Thetis Profiler is a submersible, vertically profiling platform for use in coastal marine and fresh water environments.

The Thetis Profiler is an autonomous moored profiler that is a submersible vertically profiling platform for use in marine to freshwater water bodies.  The platform is designed to sample the water column distributions of physical, biological, chemical and optical properties at a fixed geographical location over extended periods of time, providing sub-meter scale vertical resolution over the water column.   The Thetis design includes a modular, self-contained, winch-driven profiling platform with an integrated control system, a power system, and a telemetry unit. It is designed to carry a number of physical, optical and biological sensors, with expansion ports for up to a total of 8 instruments. Since the Thetis is a completely self-contained profiler the recovery, deployment and maintenance of the unit is greatly simplified.

Key aspects:

  • Operates in water depths of 5-100 m
  • Can profile in horizontal water current speeds up to 0.65 m/s
  • User configurable profiling speeds (1-30cm/s)
  • Freewave, Iridium, and cell telemetry options available
  • Supports a suite of science instrumentation
  • Easily deployable from a small vessel
  • Remote control of profiling mission parameters

 

University of Minnesota uses AMP in the Great Lakes:

First Continuous Data Collection In Lake Superior

 

Most Recent Data

WET Labs scientists, Michael Twardowski and James Sullivan, recently deployed an AMP system off San Diego, CA as part of an Office of Naval Research project to support real-time collection of optical data for model performance prediction.  The profiler was deployed in ~ 30m water depth on 19 September 2012, located about 1km offshore of the Scripps Institute of Oceanography pier, offshore of La Jolla, CA.  The science sensor suite included a CTD, downwelling irradiance, chlorophyll fluorometer, backscattering, and beam attenuation sensors.  A RF radio link was used for real-time data offload and control of the AMP.  The AMP typically performed 4 profiles per day during the daylight hours. The profiler was recovered on 12 December 2012. The plots show the time series of some of the data collected over the 95 day deployment.   AMP was serviced in early November to replace the on board batteries.

 

The list below includes (as applicable) the current product brochure, manual, and quick guide; software manual(s); and application notes.

How much on board memory does the Thetis have?

On-board memory is:

  • 2 GB for the science and Thetis controller data
  • 2 GB for the winch system engineering data.

What vertical resolution in the environmental sensor data can the Thetis provide?

To first order, the vertical resolution is set by the vertical profiling speed. The profiling speed is user configurable (which can be changed during the deployment). At typical profiling speeds of 20 cm/sec, the Thetis Profiler provides the required 0.25 m vertical resolution (even with the slowest 1 Hz sensors).

What is the common or base environmental sensor suite, and what options are there for other sensors?

The base sensing suite includes a FastCat CTD, a combined fluorescence and turbidity sensor, and a PAR sensor.  The current supported list of instruments for Thetis include:

  • CTD: SeaBird FastCat CTD (SBE49)
  • Dissolved oxygen:  SeaBird SBE43 or SBE63
  • Chlorophyll:  Sea-Bird Scientific ECO or WETStar series
  • CDOM: Sea-Bird Scientific ECO or WETStar series
  • Turbidity: Sea-Bird Scientific ECO series
  • Optical absorption and attenuation:  Sea-Bird Scientific ACS
  • PAR: ECO PARS (Sea-Bird Scientific)
  • Nitrate: Satlantic SUNA V2
  • Irradiance and Radiance:  Satlantic OCR and HOCR
  • 3-axis velocity:  NortekUSA Aquadopp

Additional sensors can be accommodated but may require NRE.  Sensors requiring flow though (pumped) measurements can be accommodated with our system.

The mounting system used for the instruments facilitates replacing sensors by the user. Adding new instruments may require new brackets.

 

Are all data collected by the instruments on the Thetis time stamped using a common clock source?

All data on-board the Thetis Profiler is time stamped using the on-board processor clock. This clock provides 10 ms resolution.  The on-board clock is synced to the shore side host controller computer during each surface telemetry session, though the user can chose to when to update the on-board clock.

What location information does the Thetis provide, and are there emergency position locator features for the Thetis?

All Thetis models include an integrated GPS system. GPS acquisition times are typically less than 2 minutes.  The GPS is only activated if a break-away condition has been detected.

There is an option to integrate an autonomous (self-contained and powered) Iridium beacon with the Thetis Profiler.

What types of telemetry systems are supported for the AMP?

The most common telemetry system utilized is a FreeWave radio system.  Transmission times for the science data are typically 20-30 seconds through the FreeWave modem when the receiver is within 3 km of the profiler.

Other telemetry systems include a broadband cellular and Iridium modems.

What is the profiling speed of the Thetis and is this configurable?

The Thetis profiling speeds are user configurable through the Sea-Bird Scientific Profiler Host software, and can be altered during any telemetry session during a deployment. The user can select profiling speeds ranging from 2 to 35 cm/sec.

hat is the endurance of the Thetis?

Our endurance is limited by the battery power and instrument configuration. We have demonstrated a 30 day endurance in testing offshore Newport, OR.

What power system is used for the Thetis?

The Thetis system uses on board batteries (BlueFin Robotics, 1.5kW) for power.

What is the profiling depth range limitation, and where has the Thetis been tested?

Our current depth operating specification for the Thetis Profiler is in water columns ranging from 5 to 100m in depth. The Thetis Profiler has been most rigorously testing in 50 m offshore of Newport, OR, though other systems have been deployed in several other locations.