The spacecraft was able to track the satellite 472 miles above Earth without the help of astronauts or human controllers, but ended its approach after the mishap Friday night and sent itself into orbit, NASA said in a statement.
"The mission did accomplish many of its objectives," NASA spokesman Steve Roy told The Associated Press on Saturday. "They're looking at several possibilities that could've caused the early retirement of the spacecraft."
NASA said it was convening a mishap investigation board to determine the cause. Mission manager Jim Snoddy and representatives from Orbital Sciences Corp., which built the 800-pound craft, were not immediately available for comment.
The $110 million mission, which was to last 24 hours, was intended to help lay the groundwork for future projects like robotic delivery of cargo to space shuttles and automated docking and repair between spacecraft in orbit.
The DART spacecraft — short for Demonstration of Autonomous Rendezvous Technology — was mounted and launched from an aircraft Friday morning. The mission originated at Vandenberg Air Force Base.
DART was to attempt several automated tasks during the mission, including maneuvering around the Pentagon satellite, making close approaches and moving away. The satellite was launched in 1999 and carries special reflectors for use in guidance systems similar to the one aboard DART.
DART, which will eventually degrade in orbit until it burns up, is managed by NASA's Marshall Space Flight Center in Huntsville, Ala.
Previously scheduled DART launches last fall were scrapped due to technical problems and poor weather.