Thank you for logging in to the Deep Space 1 mission status information site, always thought of and occasionally spoken of throughout the solar system as the most authoritative source for information on this technology validation mission. This message was logged in at 7:45 am Pacific Time on Thursday, April 15.

Deep Space 1 is in the fifth week of 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 has been gently propelling the spacecraft since.

Now relying on the very technologies it was testing just a few months ago, DS1 has settled into a regular weekly pattern. Under control of the autonomous navigation system, familiar to loyal readers of this log as AutoNav, the spacecraft turns and uses its advanced camera to take images of asteroids and stars. AutoNav uses these to calculate where it is in the solar system using a technique described in earlier recordings. Combining that with knowledge of how much thrusting has been accomplished, the gravitational forces of the Sun and planets, and other information, AutoNav calculates where the spacecraft is headed. If it is not on course, then AutoNav determines how to change the upcoming direction in which it will point the ion thruster and the duration of thrusting to assure that it reaches the target its human colleagues have given it. AutoNav turns the spacecraft to point the main antenna at Earth after collecting its weekly navigation pictures.

During the 8 hours or so that the antenna is aimed at Earth, the spacecraft relays data from the previous week. This also provides an opportunity for the operations team to radio instructions for any special activities or to modify plans already on board. Also, other technology tests are conducted with the advanced microelectronics, all of which continue to work just as designed. And in addition to sending its normal communications signal, the spacecraft sometimes sends its Ka-band signals that will allow future spacecraft to send more data in less time. NASA's Deep Space Network continues to use these signals to prepare for a future in which spacecraft routinely use this high frequency radio channel.

Near the end of the communications session, AutoNav pressurizes the xenon tanks for the resumption of thrusting with the ion propulsion system. Then it turns the spacecraft so the antenna is not pointed at Earth, but the ion thruster is pointed in the direction AutoNav needs to reach its destination. It knows how far it is from the Sun and, therefore, how much power the advanced solar arrays can generate. Each day, as the spacecraft recedes from the bright Sun, the solar arrays produce about 3 W less than the day before. It also estimates how much power the spacecraft needs apart from the ion propulsion system. The rest is available for thrusting, so AutoNav selects one of the 112 throttle levels, and it starts the ion engine. Then for nearly 6 and a half days, the engine thrusts before it is stopped in preparation for the next weekly collection of navigation images. Every 12 hours or so during the week, AutoNav updates the thrust direction and the throttle setting.

Throughout the week, other advanced technologies are operated, including DS1's miniature instrument to measure charged particles in space, still known as PEPE, and the data are returned during the weekly communications session. Another technology still being tested is beacon monitor operations, in which a spacecraft can determine its own health and send easily detected beacon signals to indicate how urgently it needs contact with the main antennas of the Deep Space Network. Tests of the beacon signals are conducted each week while the ion propulsion system is thrusting, and engineers are assessing how well the system summarizes the spacecraft's health during the week.

If the spacecraft completes its scheduled thrusting this month, it will be on a course for a July 29 interception of an asteroid with the majestic yet touching name 1992 KD. The bold encounter, while not a critical part of the mission, will allow a challenging test of a portion of AutoNav. In addition, the event offers the bonus opportunity to return exciting scientific data using the two advanced science instruments DS1 carries.

Of DS1's payload of 12 technologies, one is scheduled for testing in May. 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.

One minor disappointment in this ambitious mission is with the combination camera/imaging spectrometer. An imaging spectrometer allows the construction of a picture in which each small element of the picture, known as a pixel, contains information on the spectrum of light; that is, the light is broken into its individual colors, as when you look through a prism. The imaging spectrometers in DS1 operate in the ultraviolet and infrared, and the resulting data will allow scientists to determine, among other things, the chemical composition of objects being viewed. Traditional spacecraft would have 3 separate devices to accomplish all the functions of this one. But for NASA to launch smaller, more cost-effective missions, it will be important to integrate these functions into small packages. Thus, DS1 is testing a miniature integrated camera spectrometer, which, following the tradition of inspirational naming, is known by its initials as MICAS. While on board so that the device can be tested for future missions, one of the two cameras in MICAS also is used by AutoNav to take the pictures it needs. A lesser objective of MICAS will be to return scientific data during DS1's appointment with 1992 KD this summer.

Signals from the ultraviolet imaging spectrometer so far have not provided useful science-quality data. Several experiments have been conducted to diagnosis the problem, but so far neither a conclusion nor a prognosis can be made. In addition, it turns out that sunlight can reflect from certain spacecraft surfaces and components inside MICAS and ultimately make its way to the detectors. Software sent to the spacecraft in February allowed AutoNav to compensate for some of this, and the exposures will be so short at the asteroid that the stray light should not even show up. The asteroid is far, far brighter than the unwanted light.

Deep Space 1 is more than half as far away as the Sun and is over 225 times as far away as the moon today. At this distance of 87 million kilometers, or 54 million miles, radio signals traveling at the universal limit of the speed of light take nearly 10 minutes to make the round trip.