Prince William Sound Field Experiment

Participants

  • Cal Poly
  • JPL/UCLA
  • Rutgers University
  • AOOS

data to be collected by Slocum

Data will help provide a regional scale view of water column structure (i.e. pycnoclines, mixed layer depths) from 0-200 m to help evaluate and improve the large scale performance of the ocean model in collaboration with Yi Chao (JPL/UCLA). Cal Poly will coordinate with Rutgers University and JPL/UCLA on optimal data formats, QA/QC of data and metadata.

data to be collected by REMUS-100

The REMUS-100 will provide regional scale view of water column structure (i.e. pycnoclines, mixed layer depths) to help evaluate and improve the large scale performance of the model in collaboration with Yi Chao (JPL/UCLA).

Observations will include CTD, currents, and chl fluorescence from 0-100 m.

Autonomous Underwater Vehicle (AUV) surveys

Principal Investigator:
Mark Moline, CALifornia POLYtechnic institute

We collected nearly continuous measurements of temperature and salinity using two autonomous underwater vehicles (AUVs), the Slocum glider and the REMUS-100 AUV.

deploying the Slocum gliderSlocum glider

The Slocum glider is a 1.8 m long torpedo-shaped winged vehicle built by Webb Research Corporation. It moves through the ocean at a forward speed of 30-40 cm/s in a "saw-tooth" gliding trajectory.

REMUS autonomous vehicleREMUS-100 AUV

Two periods of the field effort were focused on the REMUS AUV operations; July 21-25 and July 29 - August 2.

The AUV was deployed to provide a regional scale view of water column structure (i.e. pycnoclines, mixed layer depths) to help evaluate and improve the large scale performance of the model in collaboration with Yi Chao (JPL/UCLA).

AUV operations during the experiment

AUV transect lines in prince william soundSlocum glider operations started July 19, 2009 and continued until August 3.

The glider was deployed in the center of the Sound and flew along a line (red line on map at right) starting south of Naked Island and ending north of the midpoint of Hawkins Island. The line is ~ 65 km long; the glider will be able to transit the line at least 4 times during the experiment. The glider will continue back and forth along this line until August 3.

REMUS-100 missions will be long transects that cover significant cross sections of the Sound. The AUV can also be deployed to map particular areas of interest (i.e. fronts, salinity wedges). A potential mission path shown above (solid yellow line) could be covered in a single deployment lasting ~10 hours.

Alternate mission ideas are shown as dotted yellow lines. After each retrieval of the vehicle, data were sent to the server at Cal Poly via cell phone modem for access and retrieval for the ocean model in collaboration with Yi Chao (JPL/UCLA).

Technical information about the Slocum glider

The Slocum glider carries a range of high-quality scientific payloads including a Sea-Bird CTD and a WetLabs ECO puck for chlorophyll and optical backscatter. The primary vehicle navigation system uses an on-board GPS receiver, with backup positioning and communications provided by an Argos transmitter.

Two-way communication with the vehicle is maintained by RF modem or global satellite phone service via Iridium. The operating range using batteries is about 500 km with a maximum depth of 200 m. The vehicle provides data when it surfaces (approximately every 3 hours), which will then be provided to the modeling groups.

Technical information about the REMUS-100

The REMUS-100 AUV is a propeller driven platform. Four 26 V/10 Ah Lithium-ion batteries power the vehicle for maximum mission distances of greater than 80 km at ~3 knots.

In addition to the batteries, the mid-section of REMUS houses the compass, heading sensors, yaw rate sensor and the PC-104 control computer. Forward of the mid-section is a 1200-kHz RD Instruments REMUS Workhorse Navigator ADCP. This ADCP consists of four upward and four downward looking transponder beams.

Upward and downward looking beam arrays are used to measure current velocity and direction in a range of user-specified depth bins above and below the vehicle. The vehicle incorporates the ADCP data to adjust for currents and calculate its position in real time while navigating. The downward looking array is also used as an altimeter, allowing for bottom tracking/mapping and fixed altitude flight. Protruding out of the pressure bulkhead against the ADCP is a Neal Brown CT sensor. Data are collected at 2 Hz with a nominal vehicle speed of 1.7 m s-1, yielding a horizontal data resolution of 0.85 m for the optical measurements. Although the REMUS has many ways of navigation (Moline et al. 2005), the primary mode of navigation will be using the onboard compass with repeated surface GPS fixes approximately every 3 km. With this surfacing interval, the mean horizontal positional error is ~ 1%.