The Royal Australian Navy (RAN) currently operates six ocean-going, diesel-electric Collins-class submarines, which are based at Fleet Base West, HMAS Stirling, south of Fremantle in Western Australia.

With significant natural resources within its 200 nautical mile Exclusive Economic Zone, and 99.9% of its bulk trade being maritime based, Australia is committed to securing the region's sea lines of communication. The RAN's mission, as part of the Australian Defence Forces, is to ensure unimpeded trade. As a result, it plays a vital role in promoting regional stability as a prerequisite for the continued prosperity of the area and of Australia itself.[1] This mission was demonstrated in 1999 when RAN submarines provided reconnaissance during the landing of UN peacekeeping troops in East Timor. At the time, it was feared that Indonesia might deploy its two Type 209/1300 vessels to the area.[2]

Australia's submarine force also plays an integral part in the RAN's mission of sea denial to hostile forces by controlling focal points in the island groups off Australia's northern coast.[3] More specifically, the six vessels are intended to provide a platform for covert surveillance reconnaissance and offensive operations against warships, submarines and merchant shipping, as well as mining and special operations support.[4] A weapons handling system designed to be able to operate Tomahawk missiles may also indicate the submarines' potential future use as land-attack platforms.[5] However, to date, no such missiles have been ordered.

The current submarine force has undergone numerous upgrades and the RAN has plans for expansion. Its most significant upgrade to date was a $600 million project ending in 2010, which involved replacing old combat systems with the Raytheon system and installing upgraded heavyweight torpedoes.[6] These additions enable the submarines to detect, acquire and track targets, as well as engage both surface vessels and submarines. In addition, the RAN plans to acquire 12 new submarines, the designs for which will be developed by the RAND Corporation.[7] Initial indications are that construction will begin around 2016 and that the new vessels will include advanced combat capabilities such as the ability to carry different mission payloads and collect intelligence.[8] The fleet expansion is said to be the "largest and most complex defence procurement undertaken in Australia's history."[9]

Sources:
[1] D.J. Shackleton, AO Vice Admiral, RAN Chief of Navy, "Plan Blue: Australia's Maritime Strategy," RAN, www.navy.gov.au.
[2] Derek Wollner, "Getting in early: lessons of the Collins submarine program for improved oversight of defence procurement," Research paper No. 3, 2001-2002, Information and Research Services, Department of the Parliamentary Library, www.aph.gov.au.
[3] Interview with Vice Admiral Don Chalmers, Chief of Navy, "Navies take up the challenge (I)," Naval Forces, 1998, Vol. 19, No. 5, pp. 50-57; in ProQuest Information and Learning Company, http://proquest.umi.com.
[4] "The Royal Australian Navy (RAN) today," Naval Forces, Supplement/Special Issue.2003; in ProQuest Information and Learning Company, http://proquest.umi.com.
[5] A.W. Grazebrook, "Australian Naval programmes revisited," Naval Forces, 1998, Vol. 19, No. 1, pp. 28-33; in ProQuest Information and Learning Company, http://proquest.umi.com.
[6] "Australia's Collins Class Subs, Submariners On Track for Upgrades," Defense Industry Daily, 15 November 2005, www.defenseindustrydaily.com.
[7] "Rand Corp. wins submarine design study," United Press International, 6 November 2009, www.upi.com.
[8] "Australia Submarine Forces," Jane's Underwater Warfare Systems, 15 January 2010, www.janes.com.
[9] "Future Submarine Design Capability Study," News and Events, Royal Australian Navy website, 4 November 2009, www.navy.gov.au.