Forward deployed naval forces now have a sophisticated Portable Undersea Training Range (PUTR) that can go where naval assets are operating rather than requiring them to travel to fixed ranges.

Procured for the U.S. Pacific Fleet by the Naval Aviation Training Systems program office (PMA-205) at Naval Air Station Patuxent River, Md., in conjunction with the Naval Undersea Warfare Center in Newport, R.I., PUTR is a self-contained, portable undersea training system composed of multiple transponders which accurately determine the position of a variety of underwater participants and weapons at a multitude of depths in undersea warfare (USW) exercises.

“The Pacific Fleet is the end user for PUTR,” says Lt. Cmdr. Charlie Kubic, the Ocean Systems Integrated Product Team Lead for PUTR. “The Pacific Ocean is vast and our Navy units are geographically dispersed. The Navy owns several cabled training ranges, of course, but they are fixed. The basic idea is that we have a training system that can be deployed wherever our units are around the Pacific. For example, we have a large force in Japan. Instead of making our submarines come to us here in the U.S. or to some other location in the Pacific to meet their training requirements, we can take a system to them. The folks who own and operate the system are stationed at the Pacific Missile Range Facility (PMRF) on Kauai, Hawaii.”

PUTR is not the first system of its kind. Its predecessor was a portable range known as the “PAR” or portable acoustic range. Kubic explains that PAR has become obsolescent and rather than revamping the outdated range, the Navy chose to acquire a new system that would improve upon the old design by having greater tracking capability, and improved maintenance and operability characteristics.

A major operational evaluation of PUTR was conducted in July at the PMRF, where it successfully met the requirements outlined by the Pacific Fleet. With a threshold of 100 nautical miles, PUTR allows naval forces to engage in a variety of scenarios over an area large enough to permit significant maneuvering. Thus, the range is capable of supporting coordinated USW training for surface ships, fast-attack submarines and aircraft. Further, it provides an ideal venue for the evaluation of sensor systems, weapons systems and crews in combat exercises.

“The test we recently ran on the system in Hawaii proved the capability of the system at that 100 square mile coverage in a relatively difficult undersea environment,” Kubic affirms. “So the minimum coverage the range will have is 100 square miles for training.”

Gains have also been made in robustness and relative efficiency, Kubic reports.

“The PUTR transponder, our acoustic listening device, is beefed up. The caging around it is more substantial, so that as the transponders are released and retrieved from the ship that deploys them, there is less chance of damage. We’ve also upgraded [lowered] the power consumption of the transponders and updated all of the associated hardware. The motherboards incorporate the latest technology and the processors are faster, allowing for the tracking of more targets, more accurately.”

The targets Kubic is talking about include submarines, surface ships, unmanned undersea vehicles, surface or undersea-launched weapons, mobile targets ,and weapons deployed by naval aircraft. PUTR not only tracks but identifies these targets.

“Basically PUTR will be used for USW exercises. You might have a submarine trying to track another submarine in the range or a submarine trying to evade surface ships or aviation assets (helicopters, P-3s). You also might have a single submarine going through its qualifications, shooting mock torpedoes in the water column. PUTR could be used for any range of USW training that a fleet unit might need to complete.”

The PAR system, limited by its older hardware, could track only three targets simultaneously in ideal conditions. If the noise level in a specific column of water was high, PAR might only be able to track two targets. The new PUTR system can reliably track four targets concurrently and more if water conditions are favorable, says Kubic.

In a typical training scenario, PACFLT would request PUTR training for forward deployed forces and the system would be deployed to their area of operations, Kubic explains.

“The PUTR system is packable in crates to be shipped out to wherever the exercise will take place. Then what we do is charter a vessel-of-opportunity. Typically we use a flat-back boat.” (Interestingly, testing of the system took place aboard the freighter Kahana, the same ship that was featured in several episodes of the ABC TV series Lost.)

“The ship would have some sort of hoist system like an A-frame on the stern or a crane, Kubic says. “We go out the day before the exercise and place the transponders on the sea floor. Then we survey them in. We know the location of the ship via GPS and send out signals to the transponders. We can measure the time that it takes for the signal to be received by the transponder and then come back. From that information and knowing the speed sound travels in a particular water column, we can locate the transponders on the ocean floor.”

Because GPS does not work underwater, PUTR tracks targets via acoustic pinging, locating vehicles throughout the water column inside the range boundaries.

“There is a specific layout that we prefer for the range to give us the best results, but it’s more important to know the exact locations of the transponders than to lay them out in a specific place,” Kubic notes. “We figure out the best area to lay out the range based on telemetry and basically place the transponders so that the range takes a hexagon shape, with one transponder in the middle.”

A transponder aboard the range support vessel serves as a hub for the array on the sea floor, tying the transponder signals together in the shipboard range operations center and sending the data via a satellite link to a shore-based remote display center.

“Using an Internet link we’ll provide real-time data to the range operation control center, which is used for command and control and evaluation of the training. It’s also important as a safety feature. The range allows you to understand where everyone is in the water column and set off alarms if people are getting too close to one another, or to let them know the exercise is over if we have a malfunction.”

Once an exercise is complete, the transponder array can be retrieved with a specific signal sent from the range support vessel. The transponders pick up the signal, interpret it and recognize a code that triggers the release of the anchors that secure them to the ocean floor. The transponders are buoyant and float to the surface, then deploy flags to aid retrieval.

PUTR is a commercial-off-the-shelf system that was developed for the Navy by L3 MariPro Inc. (an L3 Communications division). The contract was awarded in the fall of 2006, and according to Kubic the only extant PUTR system will become operational in November.

“The requirement called for a single range. Now that we’ve had a successful test we’ll see if training requirements lead to the decision to procure more systems.”