Using acoustic ranging to the instruments on the CTD it was possible to locates its position on the seafloor to within about 10m. Additionally we had an acoustic beacon that could be attached to the trawl wire and used to track the movement of the grapple as it was dragged over the sea floor. This would give us a much better chance than usual and preparations for the recovery attempt were started.
Later that day the grapple was lowered to the seafloor. Guided by data from the beacons instructions were passed to the winch operator and ships navigator to manoeuvre the grapple to the location of the CTD. Then the trawl line started to be winched in again. Two hours later the data from the beacon on the CTD indicated that the grapple had worked and the CTD too was rising suspended by 1000m of cable below the grapple. Once the grapple was brought carefully back up to the ship, the slow process of hauling in the broken CTD wire could begin. Finally, the CTD with all 32 instruments was back on board again 55 hours after the cable snapped. A great team achievement by all of the officers, crew and technicians.
We are currently preparing the new CTD for its first profile. Hopefully this one will be less eventful than the last!