Ocean Infinity Finds Argentine Submarine, After Not Finding MH370

About one year after its disappearance, one of Ocean Infinity’s (OI’s) autonomous underwater vehicles (AUVs) has detected the remains of the missing Argentine submarine, the ARA San Juan. From Ocean Infinity’s website:

Ocean Infinity, the seabed exploration company, confirms that it has found ARA San Juan, the Argentine Navy submarine which was lost on 15 November 2017.

In the early hours of 17 November, after two months of seabed search, Ocean Infinity located what has now been confirmed as the wreckage of the ARA San Juan. The submarine was found in a ravine in 920m of water, approximately 600 km east of Comodoro Rivadavia in the Atlantic Ocean.

Oliver Plunkett, Ocean Infinity’s CEO, said:

“Our thoughts are with the many families affected by this terrible tragedy. We sincerely hope that locating the resting place of the ARA San Juan will be of some comfort to them at what must be a profoundly difficult time. Furthermore, we hope our work will lead to their questions being answered and lessons learned which help to prevent anything similar from happening again.

We have received a huge amount of help from many parties who we would like to thank. We are particularly grateful to the Argentinian Navy whose constant support and encouragement was invaluable. In addition, the United Kingdom’s Royal Navy, via the UK Ambassador in Buenos Aires, made a very significant contribution. Numerous others, including the US Navy’s Supervisor of Salvage and Diving, have supported us with expert opinion and analysis. Finally, I would like to extend a special thank you to the whole Ocean Infinity team, especially those offshore as well as our project leaders Andy Sherrell and Nick Lambert, who have all worked tirelessly for this result.”

Ocean Infinity used five Autonomous Underwater Vehicles (AUVs) to carry out the search, which was conducted by a team of approximately 60 crew members on board Seabed Constructor. In addition, three officers of the Argentine Navy and four family members of the crew of the ARA San Juan joined Seabed Constructor to observe the search operation.

Ocean Infinity had committed to conduct the search operation for up to sixty days, and to take on the economic risk of the search, only receiving payment if the submarine was found.

Position Estimates from Acoustic Measurements

The debris field is centered at (-45.9499,-59.7730). Meanwhile, after analyzing the hydro-acoustic data from CTBTO sensors that was collected on Nov 15, 2017, the hot-spot was estimated to be centered at (-46.12,-59.69). That’s a distance of only 20 km, which is an impressive demonstration of the capabilities of the hydro-acoustic analysis.

There was a test explosion on Dec 1, 2017, that was used to calibrate and verify the position estimation model. The position error of the test explosion was 37 km. Therefore, the position error for the debris field was well within what was expected based on the test explosion.

An interesting description of the CTBTO’s hydro-acoustic analysis is presented here.

Implications for the Search of MH370

Unfortunately, the acoustics generated by the impact of MH370 on the ocean surface would not propagate along the “deep sound channel” (DSC) the way an underwater acoustic event does, so the impact likely was not detected by CTBTO sensors.

The San Juan’s debris field was detected earlier this month only after an AUV mission was conducted in a deep trench that was previously scanned from a higher altitude in September. The ability to skim about 100 meters above the challenging surface contour allowed the side scan sonar sensors in the AUV to collect data at the proper altitude to achieve the required image resolution. Because of its limited ability to glide above steep slopes, this resolution would have been very difficult to achieve using a “towfish”, which is a cable-towed underwater vehicle that is similarly equipped with side scan sonar sensors, but is much more limited in maneuverability than an AUV.

The initial seabed search for MH370 was conducted by the vessels Fugro Discovery, Fugro Equator, and GO Phoenix, each using a towfish. These vessels scanned about 120,000 square kilometers of seabed using this technology. Based on the failure of OI to detect the San Juan’s debris field until an AUV mission was conducted in a trench, we have to at least consider the possibility that that the debris field for MH370 was passed over in the initial search but was not detected due to challenging terrain.

In the coming weeks, we’ll learn more about what worked and didn’t work in the search for the San Juan. That knowledge should be applied to MH370 to determine if we can confidently eliminate all of the seabed that has been previously searched.

Update on November 18, 2018

The ATSB did provide statistics for estimating the confidence of detecting MH370 in the 120,000 square kilometers that were initially scanned primarily by towfish. Those statistics are presented in the figure below. About 97.4% of the total area had a detection confidence of 95%, based on the ability to detect a debris field with dimensions of 100 meters by 100 meters. About 2.1% of the area had a detection confidence of 70%, mostly due to difficult terrain, environmental conditions, or degraded data. About 0.5% of the area had no data. The aggregate probability to detect MH370 in the 120,000 square kilometers is therefore about 94%. Although this is high, it is not 100%.

Don Thompson and Mike Exner provided helpful comments for this article.