A Final Holiday Treat

Todd J. Barber, Cassini lead propulsion engineer

Happy New Year from the Cassini team at JPL! One of my New Year’s resolutions is to get a bit more up to date with this column, so if you’ll allow me one last indulgence, I’ll highlight a busy December of 2008 and then start fresh in 2009. We began the month with a multi-instrument blitz in observing Saturn’s north polar region, along with non-targeted flybys of Calypso and our old friend, Enceladus. Auroral movies of Saturn and a close Titan flyby all took place during the first week of December as well. The Titan-48 flyby was a scientific tour-de-force, including observations of the Tui Regio portion of Xanadu, potentially a “hotspot” of cryovolcanic activity, if you’ll pardon the oxymoron. This flyby was the only Titan equatorial daytime pass during the prime and extended missions, offering unique geometry for our eager scientists and their obliging instruments.

Even with a spate of propulsive maneuvers, Cassini science continued unabated in the brief but all-too-familiar sixteen days between Titan flybys in December. Our infrared and visible-light instruments looked for Saturnian ring spokes, observed a Tethys eclipse, snapped an F-ring movie -- all in few days’ work while orbiting the ringed planet! The Cassini team on Earth remained as busy as the spacecraft itself, including a significant redesign of the Cassini website and participation in the annual American Geophysical Union meeting in San Francisco (where Cassini results often steal the show).

For the final Titan flyby of the year, T49, radar again took center stage, with altimetry measurements over Ontario Lacus. Similar in size and shape to Earth’s own Lake Ontario, this feature in Titan’s southern hemisphere boasts a liquid lake of methane and ethane. These radar data can help in determining the slopes of shorelines around this lake, useful for understanding the flow of liquid hydrocarbons in and around Ontario Lacus. Altimetry measurements over the lake itself can reveal the extent of liquid methane and ethane. Just as, for example, Earth’s oceans are at the same Earth-relative elevation (i.e., sea level), liquid on Titan within a lake should have the same elevation (waves notwithstanding).

As a final holiday treat for the flight team, the propulsive maneuver planned for the afternoon of December 24, 2008 was able to be canceled with minimal cost. Yes, Virginia, even 900 million miles from Earth, there is a Santa Claus. Happy 2009 to you and yours and best wishes from your faithful explorers of the Saturnian system!