On 28 April 1950 she was transferred to the Military Sea Transportation Service (MSTS) as USNS General R. E. Callan (T-AP-139).

General R. E. Callan sailed from San Francisco 25 September 1944 with Army troops and debarked them at Oro Bay and Langemak Bay, New Guinea, on-loading at the latter port 2,700 troops and casualties which she put ashore at San Francisco 1 November on her return.

General R. E. Callan then stood out 23 March 1945 with more than 3,000 fighting men bound for Melbourne, Australia; Calcutta, India; and Trincomalee, Ceylon; returning via Fremantle, Australia; Manus, Tinian, Saipan, Guam, and Pearl Harbor to moor at San Francisco 28 June.

On 26 September she stood out to eastward, touching Karachi, India, via the Suez and returning to New York with a full load of veterans on 21 November.

After a round-the-world troop rotation cruise which brought the ship to Karachi, Singapore and Hawaii after her departure 7 December 1945 from New York, General R. E. Callan moored at Seattle on 30 January 1946.

[2] In January 1948 USAT General R. E. Callan responded to a distress signal from Army Transport Joseph V. Connolly which was burning at 39°48′N 54°37′W / 39.800°N 54.617°W / 39.800; -54.617, some 890 nautical miles (1,650 km; 1,020 mi) east of New York.

General R. E. Callan was transferred to the Air Force 15 July 1961, and rebuilt at Bethlehem Shipbuilding, Brooklyn as a Missile Range Instrumentation Ship.

During the late 1970s and early 1980s RCA Service Corp had the contract for supporting the electronics with a contingent of approx 50 personnel.

This system allowed for computer-aided steering of the three antennas to maintain 'target convergence' in compensation for the forces inflicted upon the ship in the roll, pitch and yaw axes by the sea motion.