In relation to the US Navy, TSO means Transmission System Operator. Its British counterpart, which means Tactical Systems Officer, is the Royal Navy term for the junior seaman officer in charge of submarine's fire control system.
Of interest, see Goatlocker.org's Dictionary of Navy Slang Compiled From Various Sources.
Stealthy, agile and armed with some of the most powerful weapons on the planet, Navy submarines and their crews play a number of roles in both war and peace time: attack, surveillance, commando insertíon, research and nuclear deterrence. Submarine operators are known as the “Silent Service,” where standards are incredibly high and victories are often kept secret.
Navy submarines are some of the most high-tech vessels in the world. They can insert SEAL teams into hostile target areas, launch ballistic missiles, take out enemy subs and ships, perform reconnaissance and rescue missions, and also serve as a platform for nuclear weapons.
Get the specs and tech of the all four classes of US Navy submarines at www.navy.com.