Mk 48 Mod 4 torpedo. In 2014, the Government of Canada purchased 12 upgrade kits that will allow the submarines to fire the Mk 48 Mod 7AT torpedoes. These radar and sonar systems were later upgraded with the installation of the BAE Type 2007 array and the Type 2046 towed array. The Canadian Towed Array Sonar (CANTASS) has been integrated into the towed sonar suite. The Upholder-class submarines were equipped with the CK035 electro-optical search periscope and the CH085 optronic attack periscope, originally supplied by Pilkington Optronics. After the Canadian refit, the submarines were equipped with Canadian communication equipment and electronic support measures (ESM). This included two SSE decoy launchers and the AR 900 ESM. Construction and career The submarine was built for the Royal Navy as HMS Upholder (S40), the lead ship of the Upholder (2400) class of submarines, the second vessel to bear the name in the Royal Navy. The submarine was laid down by Vickers Shipbuilding and Engineering Ltd (VSEL) in February 1983 and launched on 2 December 1986. During construction, work on the submarine was delayed due to a labour strike. Upholder commissioned into the Royal Navy on 7 December 1990. Her commissioning was delayed due to a problem with the operation of the torpedo tubes, which had to be welded closed to prevent sea water entering the submarine. Upholder was decommissioned on 29 April 1994 as a financial measure, following the end of the Cold-War and subsequent cancellation of the programme and amidst some controversy. The entire class was declared surplus to requirements in 1994. Royal Canadian Navy The British government was looking to discontinue the operation of diesel-electric boats and offered to sell Upholder and her sister submarines to Canada in 1993. The offer was accepted in 1998. The four boats were leased to the Canadians for US$427 million (plus US$98 million for upgrades and alteration to Canadian standards), with the lease to run for eight years; after this, the submarines would be sold for £1. Problems were discovered with the piping welds on all four submarines, which delayed the reactivation of Upholder and her three sisters. Upholder was the last to be restored. When work commenced on the submarine, internal steelwork was found to be corroded, hull valves were cracked, air turbine pumps were defective, and equipment was missing that had been used to refit sister boat (ex-Ursula). Upholder was renamed HMCS Chicoutimi,