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October 4, 1997 Press Contact: Steve Koppes
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University of Chicago instrument will unveil mysteries of Saturn’s rings

When NASA’s Cassini spacecraft begins winging its way toward Saturn later this month, it will carry on board an instrument–designed and built at the University of Chicago’s Laboratory for Astrophysics & Space Research–that will delve into the mysteries of Saturn’s rings. The launch is currently scheduled for Monday, Oct. 13, and the spacecraft will reach Saturn in June 2004, after a seven-year interplanetary voyage.

Scientists from LASR, in the University’s Enrico Fermi Institute, also built the Alpha Proton X-ray Spectrometer, now roving the surface of Mars and analyzing the chemical composition of Martian rocks and soil.

Cassini’s High Rate Detector (HRD) instrument, built by the University of Chicago’s John Simpson and Anthony Tuzzolino, is part of a larger instrument, the Cosmic Dust Analyzer, from Germany, that will collect and analyze the dust particles that abound in interplanetary space and form the major components of the Saturnian ring system.

The rings of Saturn are one of the most recognizable and most mysterious features of the sixth planet in our solar system. The Cassini mission, only the fourth spacecraft to visit Saturn, will be the most detailed exploration to date of Saturn’s rings, moons and icy satellites.

Explorations of Saturn by Pioneer 11 and by the Voyager 1 and 2 spacecraft showed Saturn’s rings to be made up of thousands of individual rings, largely composed of ice particles ranging in size from dust grains to large boulders. “One big question that hasn’t yet been answered,” said Simpson, the Arthur Holly Compton Distinguished Service Professor Emeritus at Chicago, “is how the rings actually formed, whether they are leftovers from planetary formation, at the one extreme, or accretions of material from outer space, at the other.”

Tuzzolino, Senior Scientist in the University’s Enrico Fermi Institute, added, “We will be able to tell the mass distribution of the particles in the rings and get an idea of which of the many theories of ring formation might be correct.”

The HRD is capable of collecting and analyzing 100,000 particles per second, and will determine the size and mass distribution of particles in the rings that range from 0.1 micron to more than 100 microns in diameter.

Cassini will be the first spacecraft to orbit Saturn, and it will make 60 tours of the planet in four years (2004 to 2008). On board Cassini is a small probe, Huygens–designed by the European Space Agency–which will descend to the surface of Titan, Saturn’s largest moon and the only one with an atmosphere. Other Cassini instruments, from several nations, will probe Saturn’s magnetosphere, get close-up pictures of other Saturnian moons and map the surface of Titan.

Cassini’s journey to Saturn includes two gravity-assist fly-bys of Venus and one each of Earth and Jupiter, which will give the spacecraft added momentum to reach its distant goal.

Instruments similar to the HRD and built at LASR flew on Vega 1 and 2, Russian spacecraft that visited Comet Halley in 1986 to gather information about the composition of the dust emitted from the comet’s coma. Another will fly on the ARGOS mission, to be launched in the spring of 1998, to measure orbital debris above Earth’s atmosphere and assess the optimal orbits for satellites and the planned space station. And finally, a fifth will be launched with the Stardust mission to Comet Wild 2 in 1998.

At age 80, Simpson has launched instruments on board three dozen spacecraft, after he witnessed the dawn of the space age as one of the organizers of the International Geophysical Year in 1957. In 1962, he founded the University of Chicago’s Laboratory for Astrophysics & Space Research.

“In the early 60s, we were the first to develop solid-state sensors in space," said Simpson. “Up until then, they were notoriously unreliable, and our success–led by Anthony Tuzzolino–led to many spinoffs. We invent and execute new space experiments, and then others pick them up.”

Simpson and his colleagues’ exploration of the solar system spans from Pioneer 2 in 1958 to Ulysses, which is currently conducting a study over the north and south poles of the Sun. Among their scientific accomplishments include the determination of the age of our galaxy’s cosmic radiation (20 million years), explorations of the size and nature of the Sun’s heliosphere of radiation and charged particles, and the study of planetary magnetospheres, including those of Earth, Mercury, Jupiter and Saturn.
Last modified at 03:50 PM CST on Wednesday, June 14, 2000.

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