Galaxy was acquired for the express purpose of research in underwater sound. Based at East Boston throughout her entire career, as a unit of the 1st Naval District, she completed a variety of assignments for the Underwater Sound Laboratory, Fort Trumbull, New London, Connecticut; experimental underwater sound work for the Bureau of Ships and the Harvard Underwater Sound Laboratory. These operations were carried out at Boston and off New London; and for a brief time off the Delaware breakwaters and in the Chesapeake Bay.
She was decommissioned and was placed "in service" on 2 August 1945, to continue her experimental assignments until placed out of service at Boston on 25 March 1946. Her name was struck from the Navy List on 1 May 1946 and she was transferred to the Maritime Commission on 20 May 1946 for disposal.