NASA launches Chicago scientists’ data-collecting instrument on Stardust

A University of Chicago instrument is riding shotgun on the first spacecraft designed to return a sample of a comet to Earth. The instrument, launched aboard NASA’s Stardust spacecraft on Feb. 7, is working properly and has already begun collecting data.

Stardust will be blasted with a hail of dust particles traveling nearly four miles per second as the spacecraft approaches within 93 miles of Comet Wild-2 (pronounced “Vilt”-2) in 2004. The main body of the spacecraft will be protected from the dust by a special shield called the bumper shield. The detectors for Chicago’s Dust Flux Monitor Instrument, or DFMI, are 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 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 & Space Research.

The DFMI registered three impact events during its first week of operation, which began Feb. 19. But it is possible the instrument was triggered by Stardust’s attitude control thrusters rather than by dust particles, Tuzzolino said.

The Chicago instrument was not originally part of the Stardust mission. Noel Hinners, vice president of 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,” said Tuzzolino. “Conditions may seem 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 spacecraft.

Scientists also will correlate the DFMI’s data with the samples Stardust will collect and return to Earth in 2006.

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 similar to Saran wrap. 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 the 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 DFMI may also be able to detect particles of interstellar dust, which NASA”s Ulysses spacecraft recently discovered streaming into the solar system.

“There is a chance that we can identify the trajectory of incoming particles that must have come from interstellar space,” said John Simpson, the Arthur Holly Compton Distinguished Service Professor Emeritus in Physics. “This is matter that is involved in the origin of the solar system itself.”

The $350,000 DFMI was funded by NASA.