STARDUST Successfully Images Asteroid Annefrank During Dress Rehearsal
Image of Asteroid 5535 Annefrank taken by the Stardust spacecraft just prior to closest approach.
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.
Stardust team waits for data to arrive from the Stardust spacecraft in the Mission Operations Room
"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
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
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.
Stardust Project Manager Tom Duxbury (left) discusses Annefrank data with Camera Lead Ray Newburn
"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".