Cornell astronomers playing important roles in Cassini mission, which will begin orbiting giant planet Saturn, June 30
By David Brand
Cassini's piercing vision reveals a never-before-seen level of detail on Titan's surface as the moon executes nearly one complete rotation under the spacecraft's watchful gaze. Complex surface markings are visible. Dark, often linear markings, with seemingly preferred orientations, cover the moon's equatorial region, except throughout the large, bright Xanadu region. Such trends in surface features are often indicative of complex internal processes. Several individual bright regions, some with faint radial patterns, can be seen upon close inspection of the images, candidates for large recent cratering events. A persistent bright feature is also observed in the movie near the South polar region where ground-based astronomers had previously detected clouds. Cassini captured the 45 images comprising this movie in the near-infrared (938 nanometers) through a polarizer filter from June 2 and June 17, 2004, from distances ranging from 14.9 million kilometers (9.3 million miles) to 7.7 million kilometers (4.8 million miles). The Sun-Titan-spacecraft, or phase, angle ranges from 66 to 61 degrees. Most of the images have been re-sized so that Titan appears to have the same width throughout the movie. The image scale ranges from 89 to 46 kilometers (55 to 29 miles) per pixel. Contrast has been slightly enhanced for visibility.
Cornell researchers are playing an important role in yet another planetary space mission, this time to Saturn, the second largest planet in the solar system. On June 30 at approximately 10:30 p.m. EDT, the Cassini-Huygens spacecraft will go into orbit around Saturn for an extensive tour of the giant planet's rings and 31 known moons.
Launched in 1997, Cassini is the best-equipped spacecraft ever sent to another planet. During the mission it will make 76 orbits around the Saturn system and execute 52 close encounters with Saturn's moons.
Cornell researchers on the Cassini imaging team are Joseph Burns, the Irving Porter Church Professor of Engineering, Theoretical and Applied Mechanics, professor of astronomy and Cornell's vice provost for physical sciences and engineering; Joseph Veverka, professor and chair of the Department of Astronomy; Steven Squyres, professor of astronomy; and Peter Thomas, senior researcher in astronomy. The team has two CCD cameras that will take pictures in visible, near-infrared and near-ultraviolet light; one is a wide-angle telescope to see broad areas, while the other sees 10 times better.
Completing the Cornell contingent are professors of astronomy Peter Gierasch, who is on the composite infrared spectrometer team, and Philip Nicholson, who is on the visual infrared mapping spectrometer team. Nicholson's instrument has much lower resolution than the CCD cameras, but it detects much longer wavelengths. It also can do a better job of determining the chemical makeup of the surfaces, atmospheres and rings.
For the critical Saturn orbit insertion maneuver on June 30, the spacecraft will fire its main engine for 96 minutes. That will reduce Cassini's speed and allow it to be captured into orbit as a satellite of Saturn. Cassini will pass through a gap between two of Saturn's rings.
The spacecraft carries a powerful scientific instrument called the Huygens probe, which will begin a long descent to the surface of Saturn's giant moon, Titan, in December. The small cone-shaped probe, which will coast for 22 days as it descends into Titan's cloudy atmosphere, carries six sensitive instruments to study the moon's atmosphere and surface. A camera will make more than a thousand images of Titan's surface and clouds. Another instrument will use radio signals to measure Titan's winds. Three sensors will analyze the moon's atmosphere. If it survives the landing, Huygens will measure Titan's surface.
The $3 billion mission is a cooperative project of 260 scientists funded by NASA, the European Space Agency and the Italian Space Agency. The science instruments will study Saturn's rings, icy satellites and magnetosphere, as well as Titan. The Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, Calif., manages the mission for NASA's Office of Space Science, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL.
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