The Pathfinder Project was a Starfleet operation conceived as a means of initiating contact with the USS Voyager after she was discovered to be stranded in the Delta Quadrant. Project Pathfinder was under the overall command of Admiral Owen Paris, and supervised by Commander Peter Harkins, based out of the Starfleet Communications Research Center. Lieutenant Reginald Barclay was also a member of the team. (VOY: "Pathfinder"}
Contact was successfully achieved with Voyager in 2376, through the use of the MIDAS Array. Initial contact was brief and sporadic, but soon, Starfleet was able to send monthly communications packets to Voyager. By 2378, daily real-time communication was possible with Voyager for 11-minute intervals. (VOY: "Pathfinder", "Life Line", "Author, Author", et al)
Through contact with Voyager during the last few years of the ship's Delta Quadrant sojourn, the Pathfinder Project was able to amass a vast database of information on the region and its inhabitants. (DS9 novel: Demons of Air and Darkness, et al)
The communications initiative was only one of a number of operations created in 2374 under the auspices of Project Pathfinder. Without the pressure of the Dominion War, Starfleet was able to devote extensive resources to the attempt to retrieve Voyager, and it was considered the top priority of the Starfleet Corps of Engineers, Starfleet Research and Development and Starfleet Science. Captain Montgomery Scott was brought on board for his expertise with transwarp drive, and Miles O'Brien, Jadzia Dax contributed their knowledge of wormhole physics. Many other engineers and scientists joined the project, working in tandem with those on Voyager and several aliens with whom the ship came into contact.
Several plans were formulated and attempted with limited success, including further attempts at utilizing the quantum slipstream drive. However, by early 2378, research into Borg transwarp technology allowed Voyager to access the Borg's network of transwarp conduits. Temporary boosts from the slipstream drive enabled the ship to exceed the maximum velocities of most Borg vessels, thereby escaping pursuit, and she safely arrived in Sector 001, greeted by much fanfare.
After Voyager's safe return, Chief O'Brien and some other engineers left for Project Restoration, but Lt. Barclay remained. With the immediate goal of rescuing Voyager accomplished, the project's importance was downgraded, but they continued regular communication with Ambassador Neelix at the New Talax colony. Over the next few years, studies of transwarp, slipstream and other technologies and scientific data brought back by Voyager eventually led to Project Full Circle.