The Full Form of DSSP is Deep Submergence Systems Project.

When the submarine Thresher was lost, a committee established under Admiral Stephan [the oceanographer of the Navy] to assess the implications of the accident concluded that the Navy did not have the operational assets to conduct missions in the deep sea. To rectify this deficiency the Deep Submergence Systems Project, initially assigned to the Special Projects Office responsibile for developing the Polaris Fleet Ballistic Missile System, was established to develop deep ocean capabilities. Subsequently other associated development programs were assigned to the Deep Submergence Systems Project office, including the development of the NR-1 nuclear powered research submarine. The intelligence community also established Deep Submergence development requirements.

A decision was made to build a second bathyscaphe, Trieste II, with the original Trieste assigned to the Deep Submergence Systems Project to test equipment that would be employed on other deep submergence systems. The new Trieste II, built at the Mare Island Naval Shipyard in September 1965, was a more sophisticated craft capable of clandestine operations in the deep ocean. When the Scorpion was lost, the previously unacknowledged Trieste II was used by the Navy to carry out the investigation. In June 1971 Trieste II was designated Deep Submergence Vehicle [DSV-1], and in May 1984 she was assigned to Submarine Development Group 1. She was moved to the Keyport Naval Undersea Warfare Center in 1985.