During the week of May 17, experts from NASA's Ames Research Center and Jet Propulsion Laboratory (JPL) pooled their expertise to conduct Remote Agent, an experiment designed to push the limits of spacecraft autonomy.

Their efforts, involving commanding of NASA's Deep Space 1 spacecraft, proved that this sophisticated artificial intelligence software is capable of achieving high-level goals by issuing spacecraft commands.

Perhaps more importantly, however, they demonstrated that Remote Agent can also play doctor, diagnosing its own problems and developing effective action plans to regain its own good health.

The latter attribute proved unexpectedly handy less than 24 hours into the experiment, when the synthetic intelligence succeeded in firing Deep Space 1's ion engine on but failed to turn it back off. With 70 percent of objectives met and the experiment paused starting the afternoon of May 18, it was clear that some type of computer bug had settled in and caused this glitch -- but what, exactly, was the problem?

In an impressive show of its own strength, Remote Agent itself provided all the clues for scientists to diagnose and resolve the situation precisely.

"Remote Agent showed us how powerful it is by providing a list of possible reasons for the bug," said computer scientist Nicola Muscettola at NASA's Ames Research Center, Moffett Field, CA, where much of the Remote Agent code was written.

Scientists found that the bug was related to a timing error when two parts of the program were exchanging information -- easy to fix permanently in coming months, and safe for completing tests the week of May 17 without immediate modifications.

"After defining the bug, our experiment team was confident we could complete the flight test. We asked Remote Agent to develop a new plan and then to fly Deep Space 1 solo for six more hours."

The happy end result: In 29 hours starting at 11 a.m. on Monday, May 17, and in six hours on Friday, May 21, the remote agent team met 100 percent of their experiment objectives.

"We ran the program about 3,000 times on Earth before the space test, and this bug never appeared," Muscettola said. "The sudden occurrence of this bug is an example of why we tested the software during space flight instead of only on the ground."

"If had not been for Remote Agent's ability to do onboard planning, we would not have been able to complete the tests so quickly. It would have taken days for the ground team to come up with a new plan," said Dr. Pandu Nayak, deputy manager of Remote Agent development at Ames.

To demonstrate Remote Agent's versatility, the tests threw unique challenges in the software's path. Scientists created four simulated failures designed to test Remote Agent's mettle to the max.

On May 17, the spacecraft's camera appeared to be stuck in the "on" position. Remote Agent craftily responded by formulating and executing a new plan that accounted for the fact that the camera could not be turned off, thus impacting total spacecraft power availability.

Then, on May 21, "when the artificial intelligence detected that an electronics unit had 'failed,' the software fixed the unit by reactivating it, not unlike rebooting a personal computer after the screen freezes," said Dr. Marc Rayman, Deep Space 1 deputy mission manager and chief mission engineer at JPL, Pasadena, CA.

"Next, a sensor 'failed,' and Remote Agent correctly recognized the sensor was the problem, not the device it was sensing. This pair of problems is akin to finding that the engine warning light has come on in your car. The light can mean one of two things: either the engine has a problem, or the sensor that triggers the light has a problem. In each case, Remote Agent correctly distinguished which situation it was in," Rayman added.

The final simulated failure was a thruster stuck in the "off" position, which Remote Agent detected and for which it compensated by switching to a different set of thrusters.

"This technology will allow us to pursue Solar System exploration missions that only a few years ago would have been considered too elaborate, too costly or too dependent on teams of Earth-bound controllers," said Dr. Doug Bernard, Remote Agent manager at JPL.