National security, health & engineering solutions company, Leidos, says it has under construction an autonomous unmanned vessel designed to track quiet diesel-electric submarines spanning miles of ocean depths for months at a time with minimal human input, and due for testing at sea in 2015. Construction on the ACTUV (Autonomous Continuous Trail Unmanned Vessel) is under a Defense Advanced Research Project Agency (DARPA) program for the design, development, and construction of a vessel originally conceived for an anti-submarine warfare mission. "ACTUV's advanced sensor technology should allow for continuous surveillance which, combined with the vessel architecture and design…