MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109 TELEPHONE (818) 354-5011
Contact: John G. Watson
FOR IMMEDIATE RELEASE
August 3, 1999
ASTEROID MYSTERY IN DEEP SPACE: SIBLINGS OR PARENT AND CHILD?
NASA's novel Deep Space 1 spacecraft not only achieved a
technology milestone when it successfully flew itself past an
asteroid last week, it gave scientists a deep-space "family tree"
mystery to ponder.
Deep Space 1 flew within an estimated 26 kilometers (16
miles) of asteroid 9969 Braille on July 28. The spacecraft's
infrared sensor confirmed that the small asteroid is similar to
Vesta, a rare type of asteroid and one of the largest bodies in
the main asteroid belt, which lies between Mars and Jupiter.
"This clear link between Vesta and Braille is an important
finding," said Dr. Laurence Soderblom of the U.S. Geological
Survey, team leader for Deep Space 1 experiments using the
spacecraft's integrated spectrometer and imaging instrument.
Scientists are now wrestling with a thorny question: Is the
near-Earth asteroid Braille a chip off Vesta's old block, or are
the two asteroids siblings which originated elsewhere, perhaps
thrown off a larger body that has long since been destroyed?
The scientists made their finding from three sets of data
collected by the spacecraft's infrared camera. Called spectra --
data obtained when the instrument breaks light into component
colors, much like a prism does -- the data sets cover different
parts of the asteroid and were taken just after closest approach.
Braille's longest side is now estimated at 2.2 kilometers
(1.3 miles) and its shortest side appears to be 1 kilometer (0.6
miles). This elongated asteroid was expected to be irregular, and
two photographs taken approximately 15 minutes after closest
encounter have helped to confirm this.
By contrast, Vesta, discovered in 1807, has a diameter of
about 500 kilometers (310 miles). The fourth asteroid ever
discovered, Vesta shares with Braille a high visual reflectivity.
In fact, Vesta is the most reflective of the main-belt asteroids.
Apart from flyby findings, project scientists have
determined that Braille is one of the asteroids that drift in and
out of Earth's orbit over eons and that it will return to Earth's
vicinity within a few thousand years.
The flyby, at 9:46 p.m. PDT on July 28 (04:46 Universal Time
July 29), occurred at an estimated distance of 26 kilometers (16
miles), although the exact distance is still being measured.
Diagnosis of an apparent target-tracking problem that affected
the taking of black-and-white photos during the flyby continues.
Preliminary results suggest that a combination of the asteroid's
highly irregular shape, its orientation relative to the Sun and
the camera's response under these unusual conditions are
Launched Oct. 24, 1998, Deep Space 1 is the first mission
under NASA's New Millennium Program, which tests new technologies
for future space and Earth-observing missions. The technologies
that have been tested on Deep Space 1 will help make future
science spacecraft smaller, less expensive and capable of more
decision-making so that they rely less on tracking and
intervention by ground controllers.
Of the 12 new technologies on board, all but the
spacecraft's autonomous navigation system had been completely
tested since launch. With the asteroid encounter, AutoNav
successfully finished its last 5 percent of testing. Science
return was a bonus for this technology validation mission.
A Deep Space 1 asteroid flyby press kit, along with mission
status reports from launch to the present, is available at:
The mission is managed for the Office of Space Science, NASA
Headquarters, Washington, DC, by NASA's Jet Propulsion
Laboratory, Pasadena, CA, a division of the California Institute