Can’t Slow Down Cassini’s Scientific Appetite

Todd J. Barber, Cassini lead propulsion engineer

In a few paragraphs, I’m going to try to cover the spacecraft highlights from a jam-packed November. Truth be told, my last installment left off just before the Enceladus-6 flyby on Halloween. I’m sure those familiar with Cassini and the Saturnian system already know what a tremendous success that flyby was, so I’ll jump right into the 11th month of 2008. On the first day of the month, our protective main-engine cover ended a flurry of autumn activity, with its last close-open cycle until October of 2009. Even though the cover cycling mechanism is somewhat beyond its design life, it continues to work beautifully in flight, protecting our twin main engines from micrometeroid mischief. Just three days after the Halloween E6 flyby, we buzzed Titan within 1105 kilometers, a bona fide one-two punch, scientifically. This flyby was primarily about acquiring radio science data, including bistatic surface scattering measurements.

A mid-month press release revealed yet another Saturnian mystery -- a massive, bright aurora that engulfs the north polar region as seen in infrared light. Both Jupiter and Earth have familiar “ring aurora,” perhaps most notably photographed by astronauts on the space shuttle. This bizarre magnetic field feature changes within tens of minutes, quite a dynamic phenomenon. Cassini observed this quirky display in extreme northerly latitudes only (above 82 degrees), a vantage point made possible by recent nearly polar orbits of Saturn. Magnetospheric scientists will have their hands full in the coming months and years with these new and intriguing data.

Many ring observations occurred early in the month as well, in addition to non-targeted flybys of Polydeuces, Telesto, and our old friend, Enceladus. Even propulsive maneuvers can’t slow down Cassini’s scientific appetite -- during Orbit Trim Maneuver #170 (OTM-170), our robotic proxy searched for radio signals from Saturn's atmosphere called "Whistlers." These are waves produced by lightning strokes; they get their name because of their unique sound when the signals are amplified and played through a speaker. They sound like a whistling tone. I’m amazed how much science can be packed into even these zippy periods with only sixteen days between Titan encounters. Speaking of Titan, mid-month we turned our scientific eyes, ears, and noses to this second-largest moon of the solar system in the T47 flyby just over 1000 kilometers in altitude. I can’t begin to describe the variety of science plans for this very special flyby, but one highlight was surely the first high-resolution imaging of the Huygens landing site by our Visual and Infrared Mapping Spectrometer. Even though the spacecraft remained busy through the end of the month, the flight team was able to take a small break. Our maneuver scheduled for Thanksgiving afternoon itself was able to be canceled, actually with a savings of propellant. Now that is something for which to be thankful!