 Unable to convert the vessels to helicopter-carrying versions like the "St. Laurent"s due to budget constraints, instead the "Restigouche"s were to receive variable depth sonar (VDS) to improve their sonar range, placed on the stern, and the RUR-5 anti-submarine rocket (ASROC).The destroyers also received a stepped lattice mast.Called the Improved Restigouche Escorts (IRE), "Terra Nova" was the first to undergo conversion, beginning in May 1965.