at the end of their course prior to joining the operational ships. The RSN has also partnered with ST Education and Training to operate the training ship STET Polaris since 2010. Polaris was specially constructed with a "dual bridge" to facilitate training requirements for two navigation teams to operate simultaneously and can carry 30 trainees and instructors; the ship was named after the North Star, which mariners had traditionally used as a navigational reference point in ancient times. While submarine training was initially conducted in Sweden by the Royal Swedish Navy, training for submariners are now conducted locally in Singapore. Submariners are trained at the Submarine Training Centre (STC) also known as RSS Challenger, named after the first submarine acquired by the RSN. It is located in Changi Naval Base and is designed to be a state-of-the-art facility featuring submarine simulators in order to enhance the realism and effectiveness of submarine training. Training in the simulators can be up to several days in order to simulate actual deployments when the submariners are training in the STC. Prospective submariners are put through a nine-month-long course which consists of a series of tough tests in order to ensure that every qualified submariner is able to meet operational requirements at sea. The simulators housed in the facility are known as the Submarine Steering and Diving Trainer (SSDT) and Submarine Combat Tactical Trainer (SCTT). The two simulators allow the flotilla to conduct training that closely simulates at-sea conditions without the logistical costs involved in deploying submarines out at sea. The SSDT is designed based on the Archer-class submarine and trains the helmsman to steer the submarine as well as the diving officer in diving the submarine while allowing the “Officer of the Watch” to oversee the entire process. The SCTT is designed to train the submariners in combat operations, which consists of four consoles modelled after those installed on board the actual submarines. These are used to train the crew in submarine combat operations such as analysis, surveillance, command and control, and weapons control. Singapore is also known to have sent prospective submarine Commanding Officers for the Royal Netherlands Navy Submarine Command Course as well as the German Navy Submarine Commanding Officer Course. A training suite for crew members of the new Invincible class submarines is now being developed, which is planned to operationalise by 2024. Like the previous simulators before it, it will