Todd J. Barber, Cassini lead propulsion engineer
Greetings from Pasadena as another holiday season is upon us! I'm nearly two months behind in summarizing some of the key science results from the Cassini mission to Saturn, but I'll do my best via this column to get you caught up. This is never easy with the steady deluge of new science data from Saturn!
Mid-September was punctuated by wonderful opportunities for radio science, including ring occultation experiments. By passing Cassini's radio signal through Saturn's rings, data about the ring particles may be revealed by the effects they had on the radio signal as it passed through on its way to Earth. It's a conceptually simple idea, but as always, the challenge is in the details.
This period also included observations by the Imaging Science Subsystem (ISS) of many of Saturn's lesser-known moons, the underdogs of the Saturnian system, if you will. These visible-light images were more about improving knowledge of satellite location than about revealing surface details. This also offered a wonderful way to kick off a month-long period with a bounty of non-targeted moon observations. Titan and Enceladus sometimes steal the show, but the dozens of other moons in orbit around Saturn are no less worthy of exploration.
Through all of this terrific science data return, engineering teams have been busy as well. For example, the last few months have been peppered with many main-engine cover cycles, a rate of usage never seen in the mission to date. Cassini occasionally encounters dust hazards in its lofty pirouettes of Saturn, typically when crossing the ring plane. Even the tiniest of particles could damage our delicate columbium coating within the Cassini main engines, due to the spacecraft's great speed with respect to the bits of dust. A deployable cover has been shuttled back and forth dozens of times in flight, forming a protective cocoon around the engines during periods of concern. The engineers who designed the cover thought of everything -- even if it were to become hopelessly stuck closed (thus precluding main-engine operation), we have the "cowboy" option of jettisoning the main-engine cover via pyrotechnic devices! Let's hope this never becomes necessary.
Despite an unbelievably busy October (more about that in future columns), we paused ever briefly on Halloween, a bona fide Cassini tradition. For some reason, we seem to celebrate this holiday more than any other. Perhaps it is because we launched in mid-October, eleven years ago and counting. Anyway, through soft drinks, appropriately scary music, ghoulish decorations, and enough sugar to tackle all the insulin in the world, the annual pumpkin-carving contest took center stage. Yet again, our Cassini Space-Craft Operations (SCO) office came up empty in our bid to win "Best in Show" at least once. I'm starting to feel like Linus in the pumpkin patch, but (as he would say) there's always next year. I can only imagine what tricks of nature and scientific treats Cassini will reveal during the next twelve months!