The AUV is 18.5 feet long and 50 inches tall and wide. It weighs approximately 11,000 pounds in air and has an active ballast and trim system to maintain neutral buoyancy. The Echo Ranger has a central pressure vessel depth-rated to 10,000 feet (3,000m) that houses the inertial navigation system (INS), vehicle electronics, and the batteries.

The Doppler velocity log, down-looking and chin beam altimeters, acoustic navigation sensors, forward ballast tank, and communications equipment are housed in the forward section of the AUV.

The vehicle's after-body section houses the motor controller, aft ballast tank, and quality control modem. The tail section houses the propulsion motor and tail fin actuators.

The payload is housed in the center bay area. The first generation payload consists of a dual frequency side-looking sonar (120/410 KHz), full spectrum sub-bottom profiler (1-6KHz), and 200KHz swath multibeam system. A custom-built controller bottle controls all sensors.

The Nickel metal hydride battery packs hold 170 Amp-hours of energy and can run the fully operational AUV for about 28 hours. Re-charge time for the battery pack is three to six hours.

Launch and Recovery
Oceaneering, based on their many years of ROV experience, designed the launch and recovery system (LARS) for the Echo Ranger. Its caged concept protects the vehicle during the critical stages of launch and recovery. Locking the AUV in place during the transit through the sea/air interface provides an additional safety factor when operating in marginal sea states.

The AUV resides in the cage at all times when on deck. Designated panels separate from the cage to allow maintenance access to the vehicle. Once pre-launch checks are complete, the Echo Ranger is raised above the host vessel bulwarks and suspended over the side. The AUV is lowered into the water until it reaches its launch depth of 100 feet (30m). A wet check-out procedure is performed, the vehicle is set free, and a "motor start" command is issued. All this takes place as the host vessel makes headway of about 1-2 knots. The forward motion ensures the host vessel is clear before the start command is given.

The Echo Ranger then powers to depth and performs the pre-planned sortie. After completing the mission, the vehicle ascends to the 100-foot (30m) depth point and deploys a tethered recovery buoy, which is recovered from the sea surface. The bowline is attached to the trolley in the LARS and the cage is lowered again to 100 feet (30m). The host vessel maintains 1-2 knots and the AUV is streamed behind the cage (by the bowline that was once attached to the recovery buoy). The vehicle is then reeled back into the cage and locked down for the remainder of the recovery process.

Once on deck, the data is downloaded and the battery charger is connected to the vehicle. Any required maintenance or equipment replacement is performed while the batteries are being charged. Mission Plans & Communication
Each dive is called a sortie and has an associated sortie plan, which is set up in advance and run through planning software that simulates the sortie. Any problems can be immediately identified and corrected before the plan is downloaded into the AUV.

During a sortie, the operator can use acoustic communications to skip or repeat steps in the plan, as necessary.

Communications between the Echo Ranger and the host vessel are achieved by Linkquest 3010 and 4010 series acoustic modems. The 3010 modems communicate health and status messages from the AUV. The surface modems are mounted on an over-the-side-mounted pole and in a tow fish. The pole modem is used mainly for shallow operations and during launch/recovery.

The tow fish assembly includes both the 3010 and 4010 modems to receive status messages and quality control data. The towfish-mounted modems are utilized for deepwater sorties to improve the communications range.

Echo Ranger Navigation
The navigation system is the product of Boeing's 30 years of experience designing autonomous vehicles. The navigation system's Kalman filter uses a loosely coupled solution from a number of external input sensors to define the vehicles position on the earth. The inertial navigation system is updated by either long base line (LBL) or ultra short base line (USBL). Update information is provided by transponders located in known locations, or from the host vessel through USBL tracking. The LBL update method is better suited to hazard (or block) surveys, while the USBL updating method is utilized for corridor mapping projects such as pipeline and umbilical surveys. Doppler velocity information is constantly being fed to the INS.

Successful Sea Trials
The Echo Ranger has completed a rigorous test program to establish the performance of the vehicle, payload, and handling systems. In addition, the AUV performed a survey at the Devil's Tower site in Mississippi Canyon 773 in 5,600 feet (1,700m) and is now available for other commercial projects.

The vehicle's navigation capability has exceeded expectations for data correlation between two systems in deep water. A recent comparison between a framed array location (six frames) and the sidescan position of the same frames yielded just 1.8m difference. The frames had been positioned on the seafloor using conventional LBL methods in a separate survey months before.