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Missions

Data Harvesting with Acoustic Modem

The Challenge

Researchers gain valuable information from battery-powered sensors deployed on the ocean floor, sometimes for months at a time. Retrieving data from these sensors typically involves sending out a ship: from a location directly above the sensor, an acoustic modem uploads or “harvests” the data from a sensor, before proceeding to the next sensor.

The Opportunity

Sending out an autonomous surface vehicle (ASV) instead of a ship reduces costs. To explore the opportunity, SeaTrac worked with Teledyne Marine to perform a joint demonstration for the Woods Hole Oceanographic Institute’s Center for Marine Robotics (CMR) annual Entrepreneur’s Showcase in July 2018.

The Mission

Together with Teledyne, the team fitted the SeaTrac ASV with a Benthos C-Band acoustic modem for communications. The acoustic modem was mounted near the bottom of the keel, to get the transducer as far below the surface noise as possible, while still protected by the keel in front. A second modem, pre-loaded with data to be collected, was anchored to the ocean floor.

The SeaTrac ASV was programmed with a mission to navigate to the sensor location and retrieve the data from the sensor. Then, the retrieved data was relayed back to shore and displayed live on the mission control software, before the ASV continued its mission and returned to the starting point.

“I was very impressed with SeaTrac’s graphical user interface work done on their mission control software to allow the operator to quickly change modem settings.”

– Dan Shropshire, Teledyne Marine

Results

The SeaTrac ASV with the Benthos acoustic modem travelled from the Woods Hole dock out to the sensor location and successfully uploaded the data from the sensor anchored to the ocean floor. The image below shows the USV returning to the dock after completing its mission.

Power and Speed: The acoustic modem draws very little power, and the modem mounting did not impact performance: the SeaTrac Development Platform supported ongoing communications with little impact to its overall power use.

Modem Settings: As part of the integration, the SeaTrac team added remote access capability to the modem. From shore, using the available RF, cellular and satellite links to the SeaTrac ASV, an operator pulled up and demonstrated the ability to change modem address, power level, and other settings in the Benthos modem as needed during a mission.

Acoustic Communications: The conditions in Woods Hole are sufficient for undersea communications. For the demonstration, data was reliably sent and received between the ASV and the subsea asset.

Conclusion

An ASV equipped with an acoustic modem provides a cost-effective tool to harvest data from subsea assets.
Joe Borden, Manager of Government Acoustic Systems, Teledyne Benthos, elaborates: “The Benthos modem is a proven and well-established acoustic modem: pairing it with an ASV as we’ve done here provides a great tool to retrieve data from the seafloor. But it’s also a live link: from shore an operator can communicate to send commands on-the-fly.”

Dan Shropshire, Teledyne Marine VP of Product Line Management, Marine Vehicles North America, adds: “The SeaTrac team got everything working quickly. I was very impressed with SeaTrac’s graphical user interface work done on their mission control software to allow the operator to quickly change modem settings.”

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