By Dr. Marc Rayman
JPL - May 4, 1999 - On Tuesday, Deep Space 1 completed a 6-week period of thrusting with its ion propulsion system. On March 15, after coasting for over 2 months, DS1's ion propulsion system was reactivated, and the system had been gently propelling the spacecraft since.
Now that the thrusting phase has been completed successfully, the spacecraft is on course for a July 29 interception of an asteroid with the inspiring yet humble name 1992 KD. The bold encounter, while not a critical part of the mission, will allow a challenging 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 one exists, for this asteroid. The address for the contest is http://www.planetary.org/news/contest-ds1.html.
The previous log explained the weekly pattern of thrusting for nearly 6 and a half days and the hiatus for the autonomous navigation system to get a fix on distant asteroids and stars.
Now that the thrusting is complete, the spacecraft will coast for most of the next 3 months. The ion propulsion system will be operated for about 20 hours in May and for a day or two in June and July.
It took less than 5 kg, or under 11 pounds, of xenon to provide the steady push for 6 weeks of thrusting. Yet with its astonishing efficiency, that was enough to have boosted the spacecraft by nearly 300 meters per second, or over 650 miles per hour.
If instead of using ion propulsion, DS1 had expended 5 kg of rocket propellant with its small conventional chemical propulsion system, the speed would have changed by just over 50 miles per hour.
With a total now of more than 73 days of thrusting behind it, Deep Space 1 has shown that ion propulsion is ready for even more ambitious flights.
Of DS1's payload of 12 exotic technologies, one is scheduled for testing later this month. The others are working well, with 7 having accomplished 100% of their planned basic testing, and the others being on schedule with at least 75% of the experimenting complete.
Tests continue on all of the technologies, in many cases simply to determine how the devices fare as they age in space. It is remarkable how well many of these formerly high-risk technologies are working, thus assuring roles for them in future exciting space and Earth science missions.
The focus of DS1's work in May will be to test that 12th technology -- an artificial intelligence system known as a remote agent. In contrast to remote control, this sophisticated set of computer programs 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 will formulate its own plans, using high levels 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 how to control it. It then executes that plan, constantly monitoring its progress. If problems develop, remote agent in many cases will be able to fix them or work around them.
If it cannot, it can request help from its sentient terrestrial collaborators. This powerful technology is the product of work by many experts at NASA's Ames Research Center and JPL, along with important contributions from Carnegie-Mellon University.
Remote agent, like the other high-risk technologies that have now been tested on DS1, promises to make space exploration of the future more productive and more exciting while staying within NASA's limited budget.
By transferring functions normally performed by people to the remote agent, a spacecraft may be more agile in responding to unexpected situations it encounters.
In addition, if NASA is to achieve its goal of launching many more spacecraft into the solar system without spending more money, it will be necessary to have the Deep Space Network devote less time to communicating with each one.
By carrying out some of the work humans now perform, remote agent will permit spacecraft to fulfill their missions without much of the time consuming communications, thus allowing the Deep Space Network to serve more spacecraft.
During the first part of May, the software for the remote agent experiment is being radioed to Deep Space 1 and loaded into its computer. Future logs will describe the experiments to be conducted.
Deep Space 1 is now more than two-thirds as far as the Sun and nearly 270 times farther than the moon. At this distance of over 103 million kilometers, or more than 64 million miles, radio signals traveling at the universal limit of the speed of light take 11.5 minutes to make the round trip.
Deep Space 1 Reports From Spacer.Com
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