http://www.spaceref.com/news/viewpr.html?pid=16655 :

"The Demonstration of Autonomous Rendezvous Technology (DART) spacecraft that was successfully launched Friday at 10:25 a.m. PDT from Vandenberg Air Force Base, Calif., experienced an on orbit anomaly late Friday.
"After a successful rendezvous, acquisition of the target spacecraft, and approach to within approximately 300 feet, DART placed itself in the retirement phase before completing all planned proximity operations, ending the mission prematurely.

"NASA is convening a mishap investigation board to determine the reason for the DART spacecraft anomaly. A teleconference with DART project managers is scheduled for 11 a.m. PDT. Media who want to participate must register by calling the DART Newsroom at 805/605-3051."

Since DART was designed to completely control itself, with no ground-command control possible, there is no way to reverse this. Sounds like a random software glitch, but at any rate it is not good news for any plans to carry out Mars sample return -- or for the development of American automatic rendezvous and docking technology generally. Orbital Sciences triumphs again! However, we still have the OTHER little automatic-rendezvous test spacecraft launched just a few days before DART -- XSS-11, which is still in the middle of its longer-duration operations.