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Deep Space 1 Mission Log - May 30, 1999


          Dr. Marc Rayman's Deep Space 1 Mission Log
          http://nmp.jpl.nasa.gov/ds1/mrlog.html

          Mission Update:

          Thank you for visiting the Deep Space 1 mission status
          information site, frequently referred to throughout the
          solar system, except in the central peak of one crater on
          Mercury and along a short stretch of the Amazon River on
          Earth, as the most authoritative site for information on
          this technology validation mission. This message was logged
          at 7:15 pm Pacific Time on Sunday, May 30.

          The mission of Deep Space 1 continues to go extremely well.
          The overwhelming majority of the mission's objectives of
          testing high-risk, high-payoff new technologies is
          complete. More tests are being conducted on many of the
          technologies however to assess how they fare as they
          continue operating in space.

          One such test on Friday gathered data on the ion propulsion
          system. This exotic system has now operated for over 74
          days and, as all loyal readers know, has shown itself to be
          a very very efficient and reliable means of propulsion. To
          measure whether the extensive use of this system has caused
          any small changes in its performance, a special experiment
          was executed in which the spacecraft turned to point the
          ion engine at Earth. The engine was operated at 5 different
          throttle levels while the Deep Space Network measured the
          Doppler shift of Deep Space 1's radio signal. This
          phenomenon, familiar to anyone who has heard the pitch of a
          siren change as it approaches or recedes from the listener,
          allows a measurement of the change in speed as the thruster
          gently pushes on the spacecraft. This will be used to
          search for subtle changes in the thrust of the engine since
          the beginning of the mission. All the sensors in DS1's
          suite of devices to measure ions and electrons as well as
          magnetic and electric fields were tuned and alert during
          the test so that comprehensive information on the ion
          engine could be collected. The ion engine is mounted on a
          pointing system that allows fine tuning the direction of
          thrust. This system was commanded to move through a
          prescribed pattern before the engine was powered on then
          again at the lowest and highest throttle levels used in the
          test. This allows for still more measurements of the
          effects on the ion propulsion system on the spacecraft's
          environment. It takes several days for the large volume of
          data to be radioed back to Earth.

          One of the technologies that has been in use since the
          first day of the mission is the advanced solar array. The
          two wings contain 720 lenses to focus sunlight onto 3600
          cells, each converting the light into electricity to power
          the ion propulsion system and the rest of the spacecraft. A
          test performed this week measured the electrical
          characteristics of some specially instrumented groups of
          cells to contribute to ongoing studies to determine the
          extent to which radiation or other hazards encountered in
          space cause the array to degrade.

          Additional tests were performed this week with other
          technologies that legions of Deep Space 1 mission log
          groupies are well acquainted with. The miniature integrated
          camera spectrometer, the plasma experiment for planetary
          exploration, the low power electronics, the sophisticated
          on/off switches, and the multifunctional structure all were
          exercised. But the primary tests on these and the other
          technologies are mostly complete, so although the systems
          were considered high-risk when they were selected for
          flight on Deep Space 1, the advanced capabilities they
          offer are now ready for inclusion in future missions.

          With most of the technology testing behind it, the
          operations team's attention is now turning to preparations
          for the July 29 encounter with an asteroid with the richly
          suggestive, yet startlingly simple, name 1992 KD. The
          primary objective of the event will be to provide the final
          test for the autonomous navigation system, known to its
          close friends as AutoNav. Since February, AutoNav has
          reliably been determining DS1's location. It does so by
          commanding the spacecraft to turn to point its camera at
          asteroids and stars and taking images of them. The apparent
          position of an asteroid relative to the much more distant
          stars allows AutoNav to calculate where it is in the vast
          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. As an example of how this is applied,
          suppose that distant trees are visible through a window in
          your house. If I took a picture from inside your house and
          showed it to you, you could find exactly where I had been
          standing when I took the picture by lining up the edge of
          the window with the distant trees. Similarly, because
          AutoNav 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. AutoNav has also
          controlled the ion propulsion system to put the spacecraft
          on course for this summer's asteroid encounter. The last 5%
          of the testing of AutoNav will come with its attempt to
          guide the spacecraft to the closest encounter ever
          attempted with a solar system body without actually landing
          on it. The encounter will be very challenging indeed, but
          whatever the outcome, it is certain to provide an excellent
          test of AutoNav. The encounter also offers the additional
          opportunity to conduct exciting science. The instruments
          Deep Space 1 carries for testing will be used to study the
          asteroid and its environment. Details of the plans for the
          encounter will be provided in future logs.

          In the meantime, however, new software to complete
          AutoNav's capabilities to conduct the encounter is in final
          testing here on Earth now. It's part of an overall upgrade
          to the extremely complex software that controls DS1. The
          spacecraft has received in-flight improvements before, and
          those successes are forming the basis for the upcoming
          installation of software. As the next step, the process of
          radioing the files containing the software to the
          spacecraft will begin next week. Much of the rest of June
          will be devoted to certifying the new software on the
          spacecraft and conducting other preparations for the
          encounter.

          And don't forget that JPL and The Planetary Society are
          conducting a contest to select a better name, if that's
          even conceivable, for 1992 KD. The contest is at
          http://www.planetary.org/news/contest-ds1.html.

          Deep Space 1 is now nearly 90% as far as the Sun and almost
          350 times farther than the moon. At this distance of over
          133 million kilometers, or about 83 million miles, radio
          signals, traveling at the universal limit of the speed of
          light, take almost 15 minutes to make the round trip.

          Thanks again for logging in!

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