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Gliders Debut at Proud Manta 11 As Data-Gathering Platforms
Full-Scale NATO Naval Exercises Employ Three Gliders To Provide Rapid Environmental Assessment and Sonar Predictions

By John Osler
Program Manager
Environmental Knowledge and Operational Effectiveness

Richard Stoner
Engineering Coordinator for Proud Manta 11
Daniele Cecchi
Glider Pilot and Software Implementation
NATO Undersea Research Centre
La Spezia, Italy

Undersea gliders, a type of AUV, are expected to change the way that navies operate at sea. A big step was taken toward that goal earlier this year when, for the first time, gliders were used in a full-scale NATO naval exercise. Proud Manta 11 (POMA 11) took place off the east coast of Sicily from February 4 to 17. This annual exercise brought together ships, aircraft and submarines from 10 NATO nations to test and refine NATO's anti-submarine detection and tracking capabilities.

This year, the NATO Undersea Research Centre (NURC) was invited to participate using three of its Slocum gliders, a platform manufactured by Teledyne Webb Research Corp. (East Falmouth, Massachusetts). The objectives were to demonstrate rapid environmental assessment of the exercise area and to demonstrate how tactical decision aids based on sonar performance predictions could be used by exercise participants. It was an excellent opportunity to conduct research using gliders in a noncombat naval exercise and to get feedback from NATO operations personnel on this new data-gathering platform.

The Need for Gliders
Today's navies are confronted with a new set of requirements in anti-submarine warfare. Modern submarines are typically smaller and quieter than their Cold War counterparts. Smaller submarines are easier to maneuver close to shore, where sonar is challenged by clutter in the environment and noise. On top of the technical challenges, militaries are being forced to cut budgets while still being asked to innovate and improve operations.

The solution to these challenges is a multipronged technological and scientific approach that will improve NATO navies' ability to find and track quiet submarines in littoral waters. Gliders are one part of the solution, along with improvements in sonar technology, more accurate meteorological and oceanographic modeling, and the development of software tools for understanding the data and planning operations. Naval forces are already investing in glider technology, as witnessed by the recent U.S. Navy contract for up to 150 Slocum gliders.

Tracks from the two shallow-water gliders (red and white) and the one deepwater glider (green), taken in the week prior to Proud Manta 11. The three vehicles collected data over a total of about 1,600 kilometers.

Gliders use changes in buoyancy to dive and climb, and are fitted with wings that generate forward propulsion in the process. The resulting path through the water column forms a triangular pattern that resembles a sawtooth. The glider's endurance, autonomy and undulating path make them ideal for gathering oceanographic CTD data.

In short, glider data can be exploited continuously in ocean prediction systems and anti-submarine warfare tactical decision aids to support and optimize naval operational planning and asset management. For example, temperature, salinity and optical data can help improve understanding of environmental conditions that impact the operational effectiveness of submarines. In particular, these data are used to generate sound-velocity profiles, which are essential information for sonar predictions.

Gliders Used at Proud Manta 11
POMA 11 used three commercial, off-the-shelf Teledyne Webb Slocum G1 gliders: two shallow-water gliders and one deepwater glider. The shallow-water gliders can operate in depths from four to 200 meters, while the deepwater version can operate in depths of up to 1,000 meters. The gliders operated continuously for 18 days during POMA 11.

The gliders are powered by alkaline or lithium batteries (for extended ranges), can cover a range of 600 to 1,500 kilometers, operate at average horizontal speeds of 0.35 meters per second (0.68 knots) and stay at sea for 15 to 50 days.

The deepwater glider was fitted with a manufacturer-supplied Sea-Bird Electron'ics (Bellevue, Washington) SBE 41 nonpumped CTD. Both shallow-water gliders were fitted with a SBE 41 CTD and optical sensors. The first shallow-water glider was fitted with a Satlantic (Halifax, Canada) Irradiance 504 and WET Labs (Philomath, Oregon) BB2 custom-wavelength ECO Triplet. The second shallow-water glider was fitted with a WET Labs BB2 ECO Triplet and a WET Labs BAM (beam attenuation meter).

The gliders are part of a NURC fleet of seven Slocum units procured in 2009 and operational since June 2010. The complete fleet went through intensive engineering trials in a marine area offshore La Spezia, Italy, as a preparation to the Recognized Environmental Picture 2010 (REP10) field experiment conducted by NURC and other partners in August 2010. In this experiment, a fleet of six Slocum shallow-water gliders was simultaneously operated to investigate different scientific issues related to adaptive sampling and characterization of optical parameters from remote sensing and gliders.

The scientific/technological results obtained from REP10 were later applied to the operational framework defined in POMA 11 this January and February. In both deployments, REP10 and POMA 11, the glider fleet was operated by a team of glider pilots who supervised the performance of the fleet and transmitted new missions to the gliders with sampling designs obtained from the numerical forecasting models.

The gliders are primarily used for undersea research and are expected to support three to four cruise deployments each year.

Proud Manta Glider Operations
The gliders operated continuously for a total of 18 days. The gliders were deployed 10 days before the Proud Manta exercise began. Predefined waypoints and individual mission characteristics were downloaded into the gliders before their first dive. Missions were then modified and updated if required by trained pilots throughout the deployment.

The two shallow-water gliders collected more than 1,000 temperature and salinity profiles each, while the deepwater glider collected approximately 500 profiles. The deepwater glider gathered data around the exercise area boundary, and the shallow gliders surveyed the interior of the exercise area, changing course based on adaptive sampling algorithms developed at NURC.

During the exercise itself, the gliders moved to a predefined patrol area just outside of the exercise area, where they continued to collect and transmit oceanographic data. Although it was highly unlikely that a glider would cause any damage to a submarine or surface ship during the exercise, the gliders were requested to operate just outside the operational area. But, given the familiarity developed by the operational community with the command and control of gliders during POMA 11, it is anticipated that the gliders will be able to share the water-space with other naval assets during future exercises. To continue this article please click here.

John Osler, program manager for Environmental Knowledge and Operational Effect'iveness at the NATO Undersea Research Centre in La Spezia, Italy, has a B.Sc. in geophysics from McGill University and a Ph.D. in geological oceanography from Dalhousie University. His research interests include seabed-interacting acoustics and techniques for rapid environmental assessment of oceanographic and seabed conditions.

Richard Stoner, the engineering coordinator for Proud Manta 2011, has been head of the Oceanography Branch of ETD at the NATO Undersea Research Centre since 1997. He graduated from Birmingham University with a master's degree in underwater communication. He oversees the maintenance, calibration and field deployment of the NURC fleet of seven gliders.

Daniele Cecchi, a glider pilot for Proud Manta 2011 and a senior scientific assistant at the NATO Undersea Research Centre in La Spezia, Italy, has a master's degree in electrical engineering and a Ph.D. in automation and robotics from the University of Pisa. Cecchi, who joined NURC in 2007, is responsible for the glider command and control center, including the development of algorithms for glider situational awareness, data processing and data visualization.

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