STARDUST Successfully Images Asteroid Annefrank During Dress Rehearsal 

November 4, 2002 

Late Friday evening Pacific time on November 2 (sic - actually November 1), 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".