English: Singapore's Ministry of Defence (MINDEF) signed an agreement with Kockums for the supply of two Archer class (formerly known as Västergötland class) submarines to the RSN on 4 November 2005. More than 20 years old and previously in reserve with the Swedish Navy, the submarines were transferred to the RSN on completion of the modernisation and conversion for operation in tropical waters. RSS Archer was relaunched on 16 June 2009 and recommissioned on 2 December 2011. The Archer class submarines are equipped with an air independent propulsion system. This enables the submarines to have longer submerged endurance and lower noise signature, enhancing the stealth capability of the submarines. The advanced sonar system allows the submarines to detect contacts at a further distance, while the torpedo system has a better target acquisition capability, which allows the submarines to engage contacts at a further range. As of 2016, the RSN conducted an upgrade programme on the Archer class submarines, including the CM010 optronic periscopes, new combat management systems, sonars and countermeasure systems, additional combat abilities, which includes the ability to fire new torpedoes and anti-ship missiles. All upgrades were concluded by late 2018 to early 2019. (Text Wikipedia)