"Sydney" was the first of four frigates selected to go under the A$1 billion FFG Upgrade, with HMA Ships "Darwin", "Melbourne" and "Newcastle" following. The upgrade features an 8-cell Mark 41 Vertical Launch System (VLS) for 32 Evolved Sea Sparrow Missiles (ESSM), upgrades to fire control and air warning radars, and replacement of the hull-mounted sonar and diesel generators. This refit commenced in 2002, but problems with integrating the frigates' anti-missile and anti-torpedo detection and defence systems meant that when "Sydney" was finished in 2007, she was initially not accepted back into service. By November 2008, the problems with the upgrade had been solved.