Launched in South Korea on 2004, and converted in Western Australia, Sirius was commissioned in 2006; three years before a purpose-built vessel would have been built, and at half the cost.

[1][3][4] Delos was leased (bareboat charter) to Teekay Shipping for operation as an commercial oil tanker until September 2005, then was taken up by Tenix Defence (which had been awarded the A$60 million conversion contract on 15 March 2005) for conversion into a replenishment vessel, which was completed 5 weeks ahead of schedule.

[3] Sirius could carry up to 34,806 cubic metres (1,229,200 cu ft) of fuel, including 5,486 cubic metres (193,700 cu ft) of helicopter aviation fuel, plus 240 tonnes of dry stores carried in a container deck designed for twelve 20-foot (6.1 m) intermodal containers.

[1][3][4] Modifications by Tenix included the fitting of two replenishment points (one on each side, allowing the underway replenishment of two ships simultaneously), installation of a helicopter deck aft of the superstructure, fitting of the container deck, addition of two 70-man lifeboats and two rigid-hulled inflatable boats (RHIBs) (the latter sourced from Westralia), and modification of the internal layout and equipment to bring it to naval standards.

[11] The 2013 Defence White Paper stated that the replacement of Sirius and HMAS Success would be brought forward.

[13] Spanish shipbuilder Navantia is offering the Cantabria design, while South Korea's DSME is proposing the downsized Aegir variant of the Tide-class tanker.

Navantia's proposal based on Cantabria was announced as the successful design in the Australian tender in March 2016, with an expected in service date for the first of two Supply-class replenishment oilers in late 2020.

[16] In September 2021 Sirius embarked on her final deployment to South-East Asia and the south-west Pacific prior to her decommissioning in December 2021.