Underwater sensor network helps track Argentina's lost submarine

Not long ago, the Argentine Navy lost contact with the "San Juan" submarine. This is a diesel-powered small submarine that was involved in exercises on the east coast of Patagonia.

About a week later, the Vienna-based CTBTO declared its international surveillance system – a network of sensors designed to detect nuclear explosions, no matter where they occur on Earth. - Listen to a sound that coincides with the explosion that occurred near the last known position of the "San Juan" submarine. The submarine contained 44 staff members at the time.

In November, the Argentine Navy’s “San Juan” submarine disappeared on the east coast of South America.

The CTBTO system has a variety of scientific applications. This is not the first time it has been put into use after a possible disaster. For example, in 2000, researchers analyzed CTBTO data to find signs of the existence of the missing Russian submarine Kursk. In 2014, they used the system to try to determine the fate of Malaysia Airlines Flight MH370.

According to Mario Zampolli, CTBTO hydroacoustic engineer, the system has 289 sites worldwide and will have 337 after it is fully built. The researchers used four different technologies: seismic and atmospheric infrasound and hydroacoustic and radioactive nuclide sites to detect traces of radioisotopes from possible explosions. All information is gathered in the International Data Center in Vienna and the analysts at the center to determine if any events of interest are associated with a nuclear explosion. These systems can record data 24/7. Signals are stored and used for various scientific applications and disaster mitigation.

Regarding how the system helped search for the "San Juan" submarine, Zampolli said that six underwater stations were equipped with hydrophones. Two of them received signals: one on the island of Ascension, south of the equator in the Atlantic Ocean, and the other from the Crowe Islands in the South Indian Ocean, between Africa and Antarctica. At the same time, since each site has three sensors, based on the time delay of the signal arriving at each sensor, the researchers can calculate which direction the signal came from. If you calculate a geodesic from these points, the intersection of the two lines will be very close to where the submarine was last contacted.

The researchers found the origin of the sound. It is estimated that it occurred 3 hours and 21 minutes after the last contact between the submarine and the base. Zampolli et al. performed a detailed analysis of the sound and made sure that it was not a natural event. It is a pulse signal - short and sharp. Some aspects of this signal are consistent with the sounds previously found in the explosion.