Thank you for visiting the Deep Space 1 mission status information site, for 120 weeks consistently the number 1 site among sentient life forms in the local group of galaxies for information on this mission of exploration and adventure. This message was logged at 12:15 pm Pacific Time on Sunday, February 11.

DS1 continues to operate extremely well on its remarkable travels through deep space. While it requires a great deal of careful planning and diligent monitoring to keep the distant probe happy and healthy, the smooth sailing has allowed the operations team to devote its energies to putting the finishing touches on upgrades for the craft's software. DS1 already has been reprogrammed four times during its voyage, each time to outfit it with new capabilities so that it could blaze new trails. The latest version of software, which goes by the sure-fire market-grabbing name M6F3, will give the spacecraft some enhancements to improve its chances of acquiring science data during the comet encounter in September that will be the extended mission's risky but exciting finale. In addition, a few improvements to make the craft easier to operate will be included, and some minor bugs that have been discovered in the current version of software will be corrected. (Of course, there aren't any major bugs, as the software on board now has allowed the spacecraft to fly nearly flawlessly since it was loaded 8 months ago.)

To prepare the software, experts test it in a Deep Space 1 simulator at JPL. This facility includes some devices that are similar to what is on the real spacecraft. Other systems are recreated with software simulations, and together they all operate with another set of software that allows the system to behave as if it were in space. It is not a perfect recreation of the actual spacecraft in the space environment, but it does allow commands that will be sent to the spacecraft to be checked out first, and in this case it allows the main computer's new software to be tested.

Next month, M6F3 will be loaded on the spacecraft. The Deep Space 1 project has reserved extra time for this with the Deep Space Network, NASA's worldwide array of huge antennas for communicating with remote spacecraft. The week of March 5 will be devoted to beaming the files with the software across the solar system to DS1, then the following week will be used to install it on the craft's central computer. This log will be updated on about March 18 with a report on the outcome of the complex and delicate process of uploading the software, rebooting the computer to begin running it, verifying its performance, and returning the craft to its operational configuration. You can look forward to finding details that will be available nowhere else in the solar system, including what kind of take-out food was provided to the operations team for the day that requires virtually all team members to be at their stations in the DS1 mission control center.

March might hold even more of interest for all Deep Space 1 fans than the tricky replacement of the software. The Learning Channel and the BBC may be broadcasting a documentary on the mission. (If we can learn the broadcast day and time in advance, we will try to put it on the DS1 Web site.) Although your devoted correspondent hasn't seen it yet, with material like this, how could it be anything other than thoroughly captivating? The documentary will focus on the primary mission, which concluded in September, 1999.

As faithful readers throughout the cosmos know, one of the many significant accomplishments of the primary mission was the testing of an advanced ion propulsion system. That system is still being used now, and on January 27, it had accumulated 365 days of operation. In that year of thrusting, the exotic system consumed only about 44 kg, or 97 pounds, of xenon propellant. Even though for a variety of reasons the propulsion system has occasionally been operated in less efficient modes, it still has managed so far to impart the equivalent of 2.6 kilometers/second, or about 5800 miles/hour, to DS1. In fact, the real function of the ion propulsion system is to change the shape of Deep Space 1's orbit around the Sun; a recording in about 4 months will explain more about this with some interesting new statistics you can use to impress members of species less familiar with the complexities of orbital mechanics.

DS1 spends most of the time now in powered flight toward the comet encounter; it turns once each week to point the main antenna to Earth for a few hours of communications before turning back to the preselected thrust direction. Those turns however consume hydrazine, the conventional rocket propellant it uses to rotate or hold itself steady. To help conserve the dwindling supply of this precious resource, we would like to reduce the amount of turning the spacecraft has to do. Engineers recognized that one way to accomplish this would be to arrange it so that the orientation of the spacecraft when it is thrusting is the same as when the antenna is pointed at Earth. In that case, no turns would be necessary to conduct the two separate activities.

As DS1 fires its ion engine to reach the comet, and Earth and the spacecraft move rapidly in their separate orbits around the Sun, how can we guarantee that some of the thrusting occurs while the antenna is pointed to Earth? Well, the ion engine and the main antenna are already bolted onto the craft, so it's a little late to change their separate pointing directions, so we need an alternate solution. Another way, of course, would be simply to move Earth so that it is aligned with wherever the antenna happens to be pointing, but with the very small budget for the Deep Space 1 project, the cost of completing the Environmental Impact Statement for that was considered prohibitive. But ever-resourceful engineers devised a less expensive strategy.

The flight plan for DS1 includes throttle levels and directions for firing the ion engine at certain times, all carefully balanced and choreographed to guide the probe to the comet. In early January we computed what the orientation of the spacecraft would be at all times throughout February if the antenna were pointed at Earth, then we determined what the effect on DS1's orbit would be of thrusting in those orientations, and finally we adjusted the flight plan for January so that the combined effect of thrusting in January and February accomplished the desired effect.

In essence, the craft has a slight zigzag in its flight profile. After zigging in January, the zag in February ends up with the main antenna facing Earth while the ion engine is firing to help the spacecraft close in on the comet. Now this does not mean we can constantly stay in touch with our remote but dear friend. The Deep Space Network is kept very busy maintaining its highly complex and finely tuned systems while it keeps Earth in contact with far-away robotic explorers. But whenever DSN time is scheduled for communications with Deep Space 1 this month, we can receive data without having to turn the craft, thus preserving the hydrazine for future needs.

DS1 is now about 280 million kilometers, or 175 million miles, from comet Borrelly. Each day, as they separately speed toward their September meeting, their separation shrinks by nearly 1.8 million kilometers, or 1.1 million miles.

Deep Space 1 is 2.2 times as far from Earth as the Sun is and about 860 times as far as the moon. At this distance of 330 million kilometers, or 205 million miles, radio signals, traveling at the universal limit of the speed of light, take over 36 and a half minutes to make the round trip.

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