In the middle of March the important test was turning over the spacecraft for the first time completely to the autonomous navigation system, AutoNav. The combination camera and imaging spectrometer has a ultraviolet detector not functioning properly, but as AutoNav turned the spacecraft it was still able to control the camera to collect pictures of asteroids and stars used to determine the spacecraft's precise location in the solar system. It analyzed these images and other data and correctly calculated its position, then predicted where the spacecraft would go if it continued on its present course. The navigation system determined what changes to make in the use of the spacecraft's ion propulsion system to keep Deep Space 1 on course. AutoNav turned the spacecraft to point the main antenna at Earth so that accumulated data on the health of the spacecraft and the results of the various technology experiments could be transmitted. Finally, AutoNav turned the spacecraft to point the ion propulsion system in the desired direction and successfully fired up the engine which had been turned off since early January except for two brief tests. Every 12 hours during each week, AutoNav updated the throttle level and the direction of thrusting, proceeding with minimal human supervision, and early each week would go through the complex sequence to determine its exact position and report to Earth.
Then on Thursday May 6, about 10:33 p.m. Central time, more than 68 million miles from Earth (over 12 light minutes), something happened and Deep Space 1 went into standby mode. AutoNav pointed the craft to the Sun, disengaged its high-gain antenna, and reverted to its low-gain antenna to communicate with Earth. By early afternoon on Friday, May 7, the Deep Space 1 operations team completed the return of the spacecraft to normal cruise configuration. The cause of the standby event that occurred is not yet known and is under investigation.
Mission controllers plan on loading of new software in the spacecraft's main computer and a flyby of asteroid 1992 KD in late July. This asteroid encounter will give the spacecraft's technologies an opportunity to be tested on a scientifically interesting body. During the flyby, AutoNav will attempt to guide the spacecraft to within five miles of the asteroid's surface, making it the closest flyby of a solar system body ever attempted.
Seven of the twelve new technologies on Deep Space 1 have completed testing, including the ion propulsion system that has proved to be 10 times more efficient than conventional liquid or solid rocket engines. To mark the occasion JPL issued a press release with the title "Exotic Technologies Finish Road Test On Cosmic Highway" proving once again that JPL is one of the less stuffy arms of NASA. Deep Space 1 will continue testing technologies until its prime mission concludes on September 18. NASA is considering a possible extended mission that would take the spacecraft on flybys of two comets in 2001.
It's one small step in the history of robotic space flight; but it may turn out to be one giant leap for computer-kind:
Artificial intelligence software was put in primary command of a spacecraft for the first time.
Known as Remote Agent, the software began operating NASA's Deep Space 1 mission and its futuristic ion engine 11 a.m. Pacific Daylight Time, May 17. The question: Can a spacecraft function entirely on its own nearly 75 million miles from Earth, without detailed instructions from the ground?
As reported in our May issue, in spite of software glitch Remote Agent successfully controlled the spacecraft and even resolved a simulated instrument failure. By the time it was halted, the experiment had already achieved approximately 70 percent of its test objectives, enough to prove that artificial intelligence software can indeed operate a spacecraft millions of miles from Earth. Perhaps more importantly, however, it demonstrated that Remote Agent can also play doctor, diagnosing its own problems and developing effective action plans to regain its own good health.
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, 1999, 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."
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.
Here is a log of events on Deep Space 1 during the ambitious artificial intelligence test.
In June the futuristic ion propulsion system on NASA's Deep Space 1 spacecraft is the winner of Discover Magazine's Award for Technological Innovation in the exploration category.
Discover magazine's annual awards, now in their 10th year, honor teams whose innovations improve the quality of everyday life. Twenty-seven technologies were selected as finalists. Nine winners, featured in Discover's July issue, were announced at a recent ceremony in Florida.
The award went to NASA's Solar Electric Propulsion Technology Application Readiness (NSTAR) program team, which developed and delivered Deep Space 1's ion propulsion system. Accepting on behalf of the team was former NSTAR manager Jack Stocky of NASA's Jet Propulsion Laboratory, Pasadena, CA.
The ion drive combines a gas found in photo flash units with some of the technologies that make television picture tubes work to deliver a thrust only as powerful as the pressure of a sheet of paper resting on the palm of a hand. Despite the almost imperceptible level of thrust, this engine, for a given amount of fuel, can increase a spacecraft's velocity 10 times more than can a conventional liquid or solid fuel rocket.
Deep Space 1, launched last October, has tested 12 new technologies, including ion propulsion, so that they can be confidently used on science missions of the 21st century.
Deep Space 1 and the Remote Agent's next task will be to chase down asteroid 1992KD on July 29.