From: LARRY KLAES (ljk4@msn.com)
Date: Tue Nov 05 2002 - 13:09:40 PST
>From: baalke@jpl.nasa.gov
>Reply-To: stardust-owner@www.jpl.nasa.gov
>To: undisclosed-recipients:;
>Subject: STARDUST Successfully Images Asteroid Annefrank During Dress
>Rehearsal
>Date: Mon, 4 Nov 2002 19:42:39 -0800 (PST)
>
>http://stardust.jpl.nasa.gov/news/news94.html
>
>STARDUST Successfully Images Asteroid Annefrank During Dress Rehearsal
>STARDUST Project
>November 4, 2002
>
>Late Friday evening Pacific time on November 2, 2002 at
>the Jet Propulsion Laboratory (JPL) in Pasadena, California, and at
>Lockheed
>Martin Space Systems - Astronautics (LMA) near Denver, Colorado, the NASA
>STARDUST flight team pulled off a tremendously successful close flyby of
>the
>main belt asteroid Annefrank. This flyby was used as an engineering test of
>the ground and spacecraft operations that will be implemented at the
>primary
>scientific target, Comet Wild 2 (pronounced "Vilt" 2) just over one year
>from now.
>
>STARDUST is a low-cost Discovery Mission that continues to perform as
>expected after more than three and a half years into a planned seven-year
>mission to rendezvous with Comet Wild 2 in January 2004. STARDUST will
>collect cometary dust samples, flowing from the nucleus just hours before
>spacecraft flyby, and return the samples to Earth in a Sample Return
>Capsule
>in January 2006. The close flyby of Annefrank offered a unique opportunity
>to thoroughly test all planned operations on the spacecraft and ground
>support operations which will be used during the rendezvous with Comet Wild
>2.
>
>"We performed a full dress rehearsal with the cometary dust collector
>deployed as we flew STARDUST within 3,300 kilometers of Annefrank," said
>Professor Donald Brownlee, the project's Principal Investigator from the
>University of Washington. "The spacecraft was poised in its flyby attitude
>with all the science instruments on. The flyby has exceeded all of our
>expectations and provided us with unexpected data about the asteroid," said
>Brownlee.
>
>The approach geometry to Annefrank was much more difficult than will be the
>case for Comet Wild 2. The spacecraft was pointed over 60 degrees off of
>the
>normal Sun and Earth pointing attitude and was running on its battery
>in order to attempt to detect and capture images of Annefrank.
>
>"The spacecraft performed every command perfectly and did everything asked
>of it," said Allan Cheuvront, Spacecraft Engineer at Lockheed Martin
>Space Systems near Denver. "We are thrilled with how well the entire
>operation went. We couldn't have asked for better performance from STARDUST
>and the images it captured of the asteroid exceeded everyone's
>expectations.
>The spacecraft's pointing, attitude and flight operations were excellent.
>This really adds to our level of confidence about how well the spacecraft
>will perform when we reach Wild 2," added Cheuvront. Cheuvront and a team
>of
>engineers at Lockheed Martin's spacecraft control center, known as the
>Mission Support Area, control the spacecraft in conjunction with JPL and
>the
>Deep Space Network.
>
>The Navigation Camera was straining to see Annefrank during approach. "This
>camera was operating at its limit of performance and seeing very dim stars
>down to about 11th visual magnitude", said Ray Newburn, the Lead Scientist
>for the camera at JPL.
>
>However, the brightness predicted by Drs. Stephen Synnott and Donald
>Yeomans
>of JPL was dimmer than 11th visual magnitude. "We tried everything we could
>think of including taking multiple long exposures and adding these on the
>ground", said Dr. T. S. Mike Wang, Optical Navigation Specialist at JPL,
>"but Annefrank was not cooperating. It was just too dim."
>
>Because of the high probability of not seeing Annefrank during the
>approach,
>the flyby was designed to be successful without having to see it up to 20
>minutes from encounter. "A flyby distance of 3,000 km (1,864 miles) was
>chosen so that there was no risk of the spacecraft flying near any possible
>dust environment or small satellites of Annefrank", said Ed Hirst, JPL
>Mission Design Manager. "We also wanted to ensure that Annefrank would be
>in
>the camera view at the start of the encounter sequence," added Hirst.
>
>Since Annefrank was not seen in the approach images, the flight team felt
>that the asteroid was at least as dim as predicted and possibly even
>dimmer.
>The team decided to send up a new encounter configuration file and set the
>initial flyby exposures longer. "We had a planned uplink six hours before
>encounter for this very purpose," said Robert Ryan, Mission Manager at JPL.
>"We had some communications problems the day before that gave us some
>difficulty, but NASA's Deep Space Network gave us highest priority, and
>excellent communications on Friday, allowing us to play back earlier images
>we missed as well as sending our final encounter commands," added Ryan.
>
>At 8:00 pm (PST) Friday evening, communications were established with the
>spacecraft to watch its pre-loaded sequence command turn the spacecraft
>away
>from the Sun and Earth into its flyby attitude. "We have built up over
>three
>years of flight experience and a tremendous amount of confidence and
>respect
>for our spacecraft to perform such operations routinely," said Joe
>Vellinga,
>STARDUST Program Manager at Lockheed Martin who led the development and
>manufacture of the spacecraft. "The spacecraft did not miss a beat during
>its flyby and it maintained all critical thermal, power, attitude, memory
>and reserves at or above design levels," added Vellinga.
>
>The main function to be tested during flyby was a sophisticated flight
>computer program that would take over control of the spacecraft to keep the
>camera view locked on Annefrank during a 25-minute period around its
>closest
>encounter. "This software was a derivative of the nucleus tracking software
>successfully flown on the Deep Space 1 (DS1) flyby of Borrelly," said Dr.
>Shyam Bhaskaran, developer of the algorithms at JPL. "Based upon my
>previous
>experience on DS1, it performed up to my expectations with this encounter
>at
>Annefrank with over 60 successful images having Annefrank right in the
>middle of each image," added Bhaskaran. David Gingerich, Flight Software
>specialist at LMA who implemented and tested the nucleus tracking software
>said, "its performance was executed just like the coach drew it on the
>blackboard."
>
>Over 70 encounter images were obtained that show a typical small solar
>system body, highly irregularly shaped and cratered. Annefrank is about
>twice as large as predicted, at least 6 kilometers in diameter, but darker
>than
>expected and therefore more difficult to detect in the early images. Not
>only did the camera perform well but the University of Chicago Dust Flux
>Measurement Instrument (DFMI) and the German Cometary and Interstellar Dust
>Analyzer (CIDA) performed as expected.
>
>Professor Tom Economou, DFMI scientist from University of Chicago, stated
>"we ran for 28 minutes as we will at Wild 2 with DFMI performing all
>expected functions". Dr. Jochen Kissel, Lead Scientist for CIDA from Max
>Planck Institute in Garching, Germany, said "I will be able to put CIDA
>into
>an even better configuration at Wild 2 based upon the Annefrank
>experience."
>Both dust instrument teams are combing through their data to see if by
>chance they may have seen a dust particle.
>
>"Performing such flight testing before the primary encounter is a critical
>part of reducing risks and significantly increasing the probability of
>success when we reach Wild 2", said JPL Project Manager, Thomas Duxbury.
>"We
>have performed exhaustive testing and training with LMA at their spacecraft
>test laboratory and through flight simulations, but these cannot totally
>replace actual flight operations testing. We learned a lot that will
>improve
>our operations at Wild 2 based upon the lessons learned at Annefrank. The
>bottom line is that if Annefrank had been Wild 2, we would have succeeded
>in
>every respect," added Duxbury.
>
>"I applaud the entire flight team," said Don Brownlee. "We could not have
>asked for more, except possibly for Annefrank to be a little brighter.
>However, for everything that we could control with the spacecraft, we were
>nearly perfect.
>
>Even though this was an engineering test, the flyby with Annefrank provided
>new information previously unknown about the asteroid about its size,
>shape,
>spin state and brightness as a function of viewing angle.
>
>"It was an exciting Friday evening for those of us involved in this
>mission," Brownlee said. "We captured images of a primitive asteroid with a
>highly significant name and one whose size turned out to be similar to the
>asteroid that likely killed the dinosaurs 65 million years ago. We have now
>validated STARDUST's systems and operations and we are eagerly awaiting our
>encounter with Comet Wild 2, just over one year from now".
>
>Asteroid Annefrank images are available here:
>
>http://stardust.jpl.nasa.gov/photo/annefrank.html
>http://photojournal.jpl.nasa.gov/catalog/PIA02885
>http://photojournal.jpl.nasa.gov/catalog/PIA02886
>
>IMAGE CAPTION
>
>Image of Asteroid 5535 Annefrank taken by the Stardust spacecraft just
>prior
>to closest approach. The gray scale figure on the right show a partially
>illuminated, highly irregularly shaped asteroid, typical of all small
>bodies
>imaged in our solar system. The STARDUST camera resolution was sufficient
>to
>show that Annefrank was about 8 km in length, twice the predicted size from
>Earth-based observations. The surface reflects about 0.1 - 0.2 % of the
>sunlight, slightly less than predicted. A few craters many hundreds of
>meters
>are seen as well as surface brightness variations due to changes in solar
>illumination as well as albedo variation. These variations are exaggerated
>in
>the false color image to the left. Both images have been digitally
>enhanced
>and resampled.
>
>For more information on the Stardust mission -- the first ever comet
>sample return mission -- please visit the Stardust home page:
>
>http://stardust.jpl.nasa.gov
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