February 2, 1999
For immediate release
Contact: Steve Koppes
Chicago instrument to get close look at comet during Stardust mission
Launch scheduled for Feb. 6
A University of Chicago instrument will be riding shotgun on the first
spacecraft designed to return a sample of a comet to Earth. NASA plans
to launch the Stardust spacecraft to Comet Wild-2 as early as Feb. 6.
Stardust will be blasted with a hail of dust particles traveling
nearly four miles per second as the spacecraft approaches to within 93
miles of Comet Wild-2 (pronounced "Vilt"-2) in 2004. A special shield
called the bumper shield will protect the main body of the spacecraft
as it passes through the glowing gas cloud that surrounds the comet's
solid nucleus. The detectors for Chicago's Dust Flux Monitor Instrument
will be mounted on the front of the bumper shield.
"There, they will be exposed to the full force of the dust flux to
measure the size of the dust particles the spacecraft encounters and
map their distribution around the comet's nucleus," said Anthony
Tuzzolino, Senior Scientist at Chicago's Laboratory for Astrophysics &
The DFMI was not originally part of the Stardust mission. Noel Hinners,
vice president of spacecraft contractor Lockheed Martin Astronautics,
suggested its addition to provide rapid measurement of the dust density
around the comet to help engineers and flight controllers assess the
health and safety of the spacecraft as it approaches the comet. Ben
Clark, also of Lockheed Martin, led the effort to find a way to
integrate the experiment and the spacecraft, the design for which was
already nearly complete.
"Our instrument performs an important health-hazard function,"
Tuzzolino said. "Conditions may be far more hazardous than we thought
as we approach the comet." If so, DFMI data will warn mission
controllers that it is time to take protective measures for the
Scientists also will correlate DFMI's data with the samples that
Stardust will collect from the comet and return to Earth in 2006.
Stardust will use a material called aerogel to collect the samples
without damaging or altering the speeding particles. Aerogel is a
silica-based solid with a porous, sponge-like structure that consists
mostly of empty space. "It is so light that it has been called 'solid
smoke,'" Tuzzolino said.
The other instruments aboard Stardust include a camera to take detailed
photographs of the comet's surface features, and the Cometary and
Interstellar Dust Analyzer, which will analyze the composition of the
comet's dust particles.
The DFMI consists of an electronics box, two detectors mounted on the
front of the spacecraft's bumper shield and two acoustic sensors,
measurements from which will be analyzed by a team headed by Professor
J.A.M. McDonnell of the University of Kent in England.
The detectors consist of a polarized plastic material. "The material is
similar to Saran wrap," Tuzzolino said. The material generates an
electrical pulse when hit by small, high-speed particles, even those
many times smaller than a sand grain.
The two acoustic sensors are embedded between layers of the shield that
protects the spacecraft from impacting dust particles. "The acoustic
sensors will be triggered by a large impact particle that hits the
shield anywhere," said LASR Senior Scientist Bruce McKibben.
Stardust will meet Comet Wild-2 at a distance of 242 million miles from
Earth, following a flight trajectory that will loop twice around the
sun. The spacecraft will loop once more around sun after its comet
encounter on the way back to Earth.
The trajectory will take Stardust close to several meteor streams that
the DFMI may be able to detect. The first such opportunity will occur
April 20, 1999 when Stardust comes within 3.5 million miles of the
Orionid meteor stream. The Orionid meteors, left in the wake of Comet
Halley, can be seen from Earth each October.
The DFMI may also be able to detect particles of interstellar dust,
which NASA's Ulysses spacecraft recently discovered streaming into the
"There is a chance that we can identify the trajectory of incoming
particles that must have come from interstellar space," said John
Simpson, Arthur Holly Compton Distinguished Service Professor Emeritus
in Physics. "This is matter that is involved in the origin of the solar
system itself. It's primordial material."
Stardust will be the 34th space-science mission Simpson and Tuzzolino
have participated in, starting with Pioneer 2 in 1958. Last November,
Tuzzolino received the NASA Public Service Medal for his role in the
development of cosmic ray and dust detectors, including the first to be
sent to Mercury, the moon, Mars, Jupiter and Saturn. All of their
experiments have been aimed at understanding the origin of elements and
matter that formed Earth's galaxy and solar system.
The DFMI is a descendant of Chicago's Dust Counter and Mass Analyzer
instrument that flew on the Soviet Union's Vega 1 and Vega 2 missions
to Halley's Comet in 1986. Simpson invented the instrument concept in
1983, with Tuzzolino playing a key role in its rapid development and
On the Vega missions, Chicago scientists discovered to their surprise
that tiny dust particles streaming from the comet had survived to the
outer bounds of the comet's coma, the spherical cloud of glowing gas
that develops around a comet's solid nucleus as it approaches the sun.
"We were able to show that the particles coming off the comet's nucleus
had to be a conglomerate, probably bound together by an ice glue,"
Simpson said. "Then, as it carried far out into space, the ice glue
dissolved, releasing the very small stuff that would have otherwise
disappeared if it had come directly from the comet."
Two other instruments related to the DFMI are components on NASA's
current Cassini mission to Saturn and on the Air Force's unclassified
Advanced Research and Global Observation Satellite.
Simpson and Tuzzolino built Cassini's High Rate Detector, part of the
larger Cosmic Dust Analyzer from Germany, which will collect and
analyze dust particles found in interplanetary space and those that
form the major components of Saturn's rings.
The ARGOS Space Dust instrument, devised by Simpson, Tuzzolino and
McKibben, will measure the mass, speed and trajectory of cometary dust
particles and man-made space debris found in low-Earth orbit when
launched later in February.
The $350,000 DFMI was funded by NASA for Stardust, the fourth mission
in the space agency's Discovery Program of smaller, faster, cheaper
missions. The Stardust scientific team is led by University of
Washington astronomy professor Donald Brownlee.
Editor's Note: An image of the researchers with a model of Stardust and
a prototype of their detectors is available upon request.
NASA Stardust home page: http://stardust.jpl.nasa.gov