Device Could Expand Oceanographic Studies with Unmanned Sensors

Oceanographers have long wanted to make measurements of the ocean’s vital signs of temperature and conductivity at varying depth to better understand storms and a host of other phenomena. The way to make such measurements is with an instrument that can rise and fall in the water column to capture data at a variety of depths. 

Such data are expensive, however, to collect from ships in the comprehensive way that oceanographers would like to make them. Thus, a chance to improve the understanding of the role of the ocean in a changing climate and to study ocean processes in regions where ship-based measurements cannot be made practically has eluded them. 

A new generation of robotic oceanographic instruments could provide an affordable alternative, but has been held back by the lack of one basic but essential component – a suitable winch.

Now Scripps Institution of Oceanography, UC San Diego, researchers report that a winch design conceived at Scripps and funded by the Office of Naval Research (ONR) has been successfully field tested and, once refined for long-term applications, is ready to facilitate a new spur of oceanographic study.

”Such device will allow us to maintain a fleet of sensors with navigation capabilities in remote areas and with an endurance dictated by the limit of the platform, a wave glider in this case. Wave gliders already have an endurance of several months, and that is expected to increase as the technology of this versatile platform evolves,” said Luca Centurioni, a Scripps oceanographer who conceived of the winch design and whose lab is overseeing its fabrication by the Denmark-based MacArtney Underwater Technology Group.

The submersible mini-winch is being tested for use with the Wave Glider unmanned surface vehicle manufactured by Sunnyvale, Calif., firm Liquid Robotics. Wave Gliders are widely used for a host of oceanographic and meteorological purposes.

Centurioni anticipates being able to mount a commonly used research instrument known as a CTD on the winch. CTDs are named for the conditions they measure: water conductivity and temperature at certain depths. Attached to the winch, they will make vertical profiles, measuring conductivity and temperature while at the same time traveling along transects pre-programmed by researchers.

"We are very excited about this development. The CTD profiling capability from the Wave Glider will help expand our capabilities to understand ocean physics,” said ONR Program Manager Theresa Paluszkiewicz.

“Integration of the submersible mini-winch onto a Wave Glider is realized through a custom embedded computer system and sensor payload package currently under development at Scripps,” said Lance Braasch, a development engineer in Centurioni’s group. “In addition to driving the winch, the computer system integrates onboard sensors to autonomously evaluate the environment. In doing so, the winch control system reduces excessive power consumption which may otherwise compromise the long term deployment capabilities of the Wave Glider.”

Researchers said they are considering the Arabian Sea, an ocean region considered too dangerous for most kinds of ship travel, as the locale of the first deployments of the new winch, which are scheduled to take place a year after Centurioni’s lab receives the winch in its final form.

– Robert Monroe

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