Thank you for visiting the Deep Space 1 mission status information site, currently regarded in the majority of the local group of galaxies as the most authoritative source for information on this technology validation mission. This message was logged in at noon Pacific Time on Wednesday, December 23.

DS1's ion propulsion system is continuing to propel this flying laboratory, but now it is under control of DS1's autonomous navigation system, developed by JPL and affectionately but unimaginatively known as AutoNav. The operations team turned the ion propulsion system off to turn the helm over to AutoNav. It began by directing the ion propulsion system to pressurize its xenon tanks for thrusting, and then commanded the spacecraft's attitude control system to turn the spacecraft to thrust in the direction AutoNav desired, and then it started the thruster. AutoNav determines how much power to devote to the ion propulsion system, which uses electricity to ionize and accelerate xenon. To do this, AutoNav has knowledge of how much power the advanced solar arrays can produce and how much power the spacecraft consumes apart from the ion propulsion system. The spacecraft will consume more power as it ventures farther from the hot Sun because it will need to operate its heaters more. In addition, each day, the ever increasing distance of the spacecraft from the Sun causes the solar arrays to generate about 8 W less than the day before. AutoNav knows how far the spacecraft is from the Sun, so it can calculate how much power is available for the ion propulsion system. Today it is at throttle level 76, and by the first week of January, AutoNav should have throttled it down to level 72. As the spacecraft continues its orbit around the Sun, every 12 hours AutoNav will update both the direction and the throttle level for the thrusting to follow the flight profile stored on board. AutoNav has operated flawlessly, demonstrating another powerful capability in DS1's set of advanced technologies.

On Monday, December 21, thrusting was suspended for a few hours during which AutoNav successfully performed another of its many functions. It commanded the spacecraft to turn to point its camera at asteroids and stars and take images of them. The apparent position of an asteroid relative to the much more distant stars will allow AutoNav later in the mission to estimate where it is in the solar system. This is based on parallax and is the same phenomenon you observe if you hold a finger in front of your face and view it through each eye separately. The apparent position of your finger shifts as you switch from one eye to the other. If you knew the exact location of your finger and of the background objects, you could determine which eye was perceiving the scene. Because the autonomous navigation system knows where the asteroids are and where the more distant stars are, it can determine where it is in the solar system when the picture is taken. The images taken this week will allow AutoNav's designers to improve on-board computer routines for processing the pictures. Previously, all they had was prelaunch predictions of the camera's performance; now, with actual images, the routines can be updated. The successful demonstrations of AutoNav's control over the ion propulsion and attitude control systems and the camera are another step in preparing NASA for an exciting future in which many of the responsibilities normally fulfilled by human controllers will be transferred to intelligent spacecraft.

A skeleton team will monitor the spacecraft over the holidays. Following the rapid development phase for DS1 and the intense activities in the two months since launch, during which many important technology validation data were collected, the operations team will attempt to recapture remnants of normal life and have some time to rest. Your faithful correspondent will remain diligent and update this log if events warrant.

During the first week of January, the ion propulsion system will be turned off. For the subsequent two months, attention will be devoted to other technology validation experiments.

Deep Space 1 is over 26 times as far away from Earth as the moon. Each day it moves over 275,000 kilometers, or more than 170,000 miles, farther from Earth. As the complex ballet of the solar system proceeds, DS1 travels about 290,000 kilometers, or over 180,000 miles, farther from the Sun every day. To continue this nerdy if not compulsive accounting, consider that because of the use of the ion propulsion system, today DS1 is about 200,000 kilometers or more than 120,000 miles farther from Earth than it otherwise would have been. And without the gentle but steady thrust of this exotic propulsion system, DS1 would be over 165,000 kilometers, or more than 100,000 miles, closer to the Sun.

Each NASA mission has a well documented set of objectives that must be satisfied. Earlier in December, DS1 met the criteria for minimum mission success. That was achieved by completing 200 hours of thrusting with the ion propulsion system and collecting extensive data on the performance of the advanced solar array, provided by BMDO, and the radio transponder built by Motorola. While other important experiments on these and other technologies have already been accomplished, and many more lie ahead, the mission now ranks as another success in NASA's long and impressive history of travels beyond Earth orbit.