@grumpyoldgeek / grizzled
The French Nuclear Attack Submarine "L'Emeraude" (Emerald) was involved in the Phase 1 search using its sophisticated acoustic detection system, which was fine tuned during the search for maximum gain at 37.5kHz using test data developed by retuning a similar detector fitted to another Rubic class sub in the Mediterranean. The detection range was then over 3,000m, but the depth that the sub operated at is not known - "classified?"
The US Navy, US Coastguard and Brazilian Navy were also involved using hardware deployed from the surface. This consequently involved the setting up of UTC (Underwater Traffic Control) to avoid any conflict, particularly with the sub.
mm43