The Applied Research Laboratory, University of Texas at Austin, Austin, Texas, is awarded a $358,450,170 cost-plus-fixed-fee modification to previously awarded contract N00024-17-D-6421 to exercise an option for research and development in support of programs throughout the Department of Defense (DOD) within its core competency areas including: (1) characteristics of the medium relative to the ocean acoustic environment; (2) high frequency sonar as applied to war fighting applications; (3) acoustic and electromagnetic properties; (4) signal and information processing; (5) navigation and precise location in space, air, water, and on land; (6) command, control, communications, computers, and intelligence; and (7) mission related and public service oriented research, technology development, test, evaluation and systems analysis. Work will be performed in Austin, Texas, and is expected to be completed by September 2027. Funds of multiple different appropriation types and years from program offices and agencies throughout DOD may be obligated on individual task orders for efforts that fall within the core competency areas. This contract was not competitively procured in accordance with 10 U.S. Code 2304(c)(1) — only one responsible source and no other supplies or services will satisfy agency requirements. The Naval Sea Systems Command, Washington Navy Yard, Washington, D.C., is the contracting activity.