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Navy divers preparing the ROV in Tonga

New Zealand Defence Force
Te Ope Kaatua O Aotearoa
Media Release
Thursday 13 August, 2009
Royal New Zealand Navy REMUS Sonar Image Of Sunken Tongan Ferry

The Royal New Zealand Navy REMUS sonar system has detected a vessel which fits the general size and shape of the missing vessel PRINCESS ASHIKA.

The Royal New Zealand Navy (RNZN) Diving and Underwater Search Team, in a combined operation with teams from the Tonga Defence Force and Royal Australian Navy Clearance Diving Team, operating from the Tongan Defence Services Vessel VOEA PANGAI, located what appears to be the sunken vessel PRINCESS ASHIKA.

The image of this is attached and shows the REMUS image of PRINCESS ASHIKA on the seabed. Note the similarity to the surface picture including bow section with ramp, bridge area and passenger compartment. The large balls in the picture are very large rock spheres. Depth is 110 metres.

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PRINCESS ASHIKA surface - shows vessel as it was. Note bridge area on top with passenger compartment underneath.

The vessel was located 11 nautical miles south southwest of Nomuka in the Ha’apai Group of islands and appears to be intact and in an upright position. The position identified by the REMUS system coincides with the positions given by both the Emergency Position Indicating Radio Beacon (EPIRB) and by the Master in his final radio call.

The Royal New Zealand Navy Diving Tender, HMNZS MANAWANUI is due to arrive in Nuku’alofa on Saturday morning and will allow the Navy Diving Team to conduct further reconnaissance operations on the PRINCESS ASHIKA using a remotely operated vehicle (ROV). The ROV will be used to conduct an examination, explore the wreck site, map the debris area and allow the diving teams to examine what further options are available. The ROV will provide images that will give 100% certainty to the identity of the sunken vessel. The RNZN Divers do not have the capability to conduct recovery operations below 50 metres.

REMUS image of PRINCESS ASHIKA on seabed - note similarity to surface picture including bow section with ramp, bridge area and passenger compartment. Large balls are very large rock spheres. Depth is 110 metres.

Background Information

What is a REMUS Underwater Robot?

REMUS is the acronym for Remote Environmental Monitoring Units. The RNZN acquired the REMUS in 2007. These are robotic ‘torpedoes’ that navigate without a human crew onboard and without cables connecting them to research vessels. They are one of the growing classes of ocean instruments known as autonomous underwater vehicles, (AUVs). REMUS vehicles can dive to 100 metres deep and are capable of conducting an 80 km survey at a speed of 3 knots. Designed by Ocean Systems Laboratory and Woodshole Oceanographic Institution in Massachusetts, USA and built by Hydroid Inc, in Massachusetts.

The REMUS is about 160cm long, 19cm diameter and weighs 37kg and has a speed of 3-5 knots (electrical battery powered); can run for 80km (about 10 hours) and uses a high frequency side scan sonar and also measures water conductivity, temperature and depth.

It is controlled with a lap top computer and pre-programmed before its dive. It navigates with acoustic transponders that are located by GPS. The REMUS is the lead weapon for mine countermeasures for the RNZN.

What is an Autonomous Underwater Vehicle?

Autonomous Underwater Vehicles (AUVs) are fundamental to the Navy’s ability to counter sea mine threats against trade routes and strategic national assets. AUVs are operated via commands that are programmed into the vehicle prior to launch, allowing the vehicle to autonomously complete a desired mission. These vehicles are equipped with sensors that gather valuable sub-surface environment data. Since modelling and simulation can assist with the tactical use of AUV systems, the Defence Technology Agency (DTA) has created a virtual simulation environment for studying the behaviour and performance of AUVs. Recommendations to assist the Navy with the optimum use of these unmanned assets are routinely provided by DTA.

What is the Remote Operating Vehicle?

The RNZN currently utilises the Sea Eye Falcon Remote Operated Vehicle (ROV) and it is best described as a tethered mini submersible. Being remotely operated they are connected to, and controlled from, the surface. The ROV is attached by an umbilical cord through which the pilot sends control orders via joystick to the various propeller thrusters that allow it to hover, turn, descend and rise under power. The RNZN ROV has small sonar in the nose that can ping out looking for things, like a sunken ship, and the pilot with his control box can look at echo returns on his screen. It also has a video camera in the nose which is invaluable for identifying/confirming what the target is they are looking at. The Falcon is very portable and as long as there is Single phase 100-270 V input it can be operated almost anywhere. Among the many features the ROV has includes a 300 metre depth rating with a 16 kilo payload, high resolution colour camera on 180 deg tilt platform, variable intensity 150 watts of lighting and a portable surface control system with video overlay and daylight readable display.

ENDS

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