Saturday, August 12, 2006

A Closer Look at Deep Space 1

There are myriad reasons why I love Saturday mornings, but one of my favorites is the Star Trek marathon on G4. There is just something comforting about sleeping in a bit and then waking up to 9 hours of TOS! So, I was watching “The Changeling” this morning and was inspired to revisit one of the Deep Space 1 Mission Logs for today’s blog entry. Dr. Marc Rayman was the chief mission engineer and deputy mission manager who kept the world informed of Deep Space 1’s progress through his mission updates.

Blog #14 by Dr. Marc Rayman
Deep Space 1 Mission Update

Originally posted May 23, 1999
Thank you for visiting the Deep Space 1 mission status information site, the most respected site in the Milky Way galaxy and among the most envied logs elsewhere in the local group of galaxies for information on this technology validation mission. This message was logged in at 12:30 pm PDT on Sunday, May 23.

The mission of Deep Space 1 continues to go extremely well. The spacecraft spent part of this past week under control of an artificial intelligence system on board that is one of the advanced technologies being tested. The testing of the remote agent accomplished 100% of the planned objectives.

In contrast to remote control, remote agent consists of a sophisticated set of computer programs that acts as an agent of the operations team on board the remote spacecraft. Rather than have humans do the detailed planning necessary to carry out desired tasks, remote agent formulates its own plans, using high level goals provided by the operations team. Remote agent devises its plan by combining those goals with its detailed knowledge of both the condition of the spacecraft and principles of how to operate it. It then executes that plan, constantly monitoring its progress. If problems develop, remote agent in many cases fixes them or works around them. If it cannot, it can request help from its sentient terrestrial collaborators.

As all dedicated readers of these logs know, on Monday and Tuesday, remote agent made its debut by formulating a plan and then executing it. When it encountered a simulated failure, a surprise challenge presented to it by the operations team, it successfully overcame it. On Tuesday, a bug in the complex software was discovered that prevented remote agent from completing the test. The flaw in the software never manifested itself during the extensive ground test program, and the successful identification and diagnosis of the bug was an important illustration of the value of testing an advanced technology on a flying spacecraft.

The bug is easily correctable for the future, but there was insufficient time to fix it and continue the tests during the window for the remote agent experiment. But once we knew about it, analysis showed that the risk of it interfering with a new test was acceptable. Taking advantage of the ease of generating a new set of goals for remote agent, the team conducted another experiment on Friday that captured all the remaining objectives for the testing of the remote agent architecture. In that experiment, remote agent was faced with 3 more (simulated) failures, each requiring a different kind of response. When it detected that an electronics unit had failed, it fixed it by reactivating it. Then a sensor failed, and remote agent correctly recognized the problem was with the sensor, 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 light has a problem. In each case, remote agent correctly distinguished which situation it was in. The last gift from the operations team was one of the small thrusters, used to control the spacecraft's orientation, being stuck closed. Remote agent correctly responded by switching to an alternate spacecraft control mode that did not depend upon the useless thruster. Remote agent accomplished other tasks during the experiment as well.

The only planned activity not conducted in the second experiment was thrusting with the ion propulsion system. The ion propulsion system behaved correctly, but software supporting the remote agent experiment apparently did not deliver confirmation to remote agent that one of its prestart commands to the ion propulsion system was executed. Therefore remote agent proceeded with the rest of its plan and correctly avoided further commanding of the ion propulsion system. The cause of the missed confirmation is under investigation, but because remote agent successfully activated the ion propulsion system earlier in the week, Friday's thrusting was not necessary for completing test objectives. The investigation has already shown that this will not affect future ion propulsion system thrusting.

With the successful achievement of all the desired testing, the experiment completed amid many references to HAL 9000 and to Star Trek.

The remote agent is the result of the work of experts at NASA's Ames Research Center and JPL, with important contributions from Carnegie-Mellon University and the Daystrom Institute. Its productive testing on DS1, as with that of the other advanced technologies, not only helps certify the technology for use on future missions, but it also gives the developers valuable experience in how things are done on an operational spacecraft, which is very different from working in a laboratory.

This weekend another calibration of the infrared system in the miniature camera/imaging spectrometer is being conducted. More technology experiments are scheduled for this coming week, but DS1 has completed the vast majority of the testing it set out to do. Still, more adventures lie ahead for the craft. When you've finished celebrating the Memorial Day weekend, be sure to check your planet's favorite mission log for an update on this week's activities and news about what is planned.

As a hint, the spacecraft continues on course for a July 29 interception of an asteroid with the powerful yet modest name 1992 KD. The daring encounter, while not a critical part of the mission, will allow a very challenging final test of a portion of DS1's autonomous navigation system. In addition, the event offers the bonus opportunity to return exciting scientific data using the two advanced science instruments DS1 has tested. JPL and The Planetary Society are conducting a contest to select a better name, if that's even conceivable, for 1992 KD.

Deep Space 1 is now nearly 85% as far as the Sun and almost 330 times farther than the moon. At this distance of 126 million kilometers, or more than 78 million miles, radio signals, traveling at the universal limit of the speed of light, take 14 minutes to make the round trip.

Thanks again for logging in.


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