As the Cassini-Hugyens spacecraft arrived at Saturn at 10:36 p.m. on June 30, among the most anxious participants was Joseph Burns, Cornell's vice provost for physical sciences and engineering. As a member of the Cassini imaging team, he has been jointly responsible for observing the gaps in two of the planet's outer rings that the spacecraft had to slip through to become the first mission to orbit Saturn.

The decision to go through these gaps in the ring debris was made on May 20 after multiple observations by Burns and his colleague at NASA-Ames, Cornell alumnus Jeff Cuzzi ’67 EP. "I am looking at the place where the spacecraft is going to make sure there is nothing there," said Burns, who is the Irving Porter Church Professor of Engineering in the Department of Theoretical and Applied Mechanics as well as professor of astronomy.

The fear was that something might have changed since May 20 in one of the two entry rings, known as the "G" ring. "We ask ourselves the question: Are we basing our orbit insertion strategy on old data?" he said.

Well before Cassini began its approach to Saturn, Burns and Cuzzi were studying images of the area taken by the Voyager spacecraft (Voyagers 1 and 2 flew past Saturn nine months apart in 1980 and 1981), as well as at ground-based observations and images taken by the Cassini camera every other day. "We were trying to see whether or not anything might have changed in the region to make sure it is still the safest place to go," said Burns.

There was jubilation at the Jet Propulsion Laboratory that night and sighs of relief from Cornell researchers as the spacecraft successfully made its perilous passage through two of Saturn's rings and went into orbit around the giant planet. The $3 billion-plus mission is the result of an international cooperation between NASA and 17 European nations. After a nearly seven-year journey, the spacecraft will make 76 orbits of the giant planet over four years, touring Saturn's rings, icy moons, and magnetosphere and sending a probe onto Titan, the planet's largest moon.

The mission, said Burns, will transform our knowledge of Saturn, with the almost certain discovery of new rings and new moons beyond the 31 already known. Voyager, he said, "essentially took a couple of beautiful photos of a glorious dance as it went by. We are going to have the motion picture."

—David Brand, Cornell News Service