Todd J. Barber, Cassini lead propulsion engineer


Todd Barber
As April draws to a close, the relatively infrequent Titan flybys we enjoyed earlier in 2009 seem a distant memory. Even though we only returned to sixteen-day orbits a bit over one month ago, the months start blurring together when Titan encounters come fast and furious. We started the month with a high-altitude (4150-kilometer, or 2579-mile) Titan-52 flyby. This offered our navigation and engineering teams a unique challenge—there were only eight days between T51 and T52! As such, we didn’t have our usual calendar time to execute a series of propulsive maneuvers to target T52—we had to nail it with OTM-186, a hybrid between a T51 “clean-up” maneuver and a T52 final targeting maneuver. I’m happy to tell you that our targeting for T52 was excellent despite these time pressures.

The Titan flyby itself went very well, largely for the benefit of radio science. Despite approaching five years in Saturnian orbit and being well into an extended mission, Cassini still manages to routinely perform “first-time” events during these flybys. T52 was no exception, with the first-ever radio science occultation near the Titan equator. I’ve talked about radio science occultations in a handful of prior columns, but in the simplest terms, by measuring the effect Titan’s atmosphere has on our return radio signal to Earth, a multitude of information can be discerned about atmospheric temperature, pressure, and even small-scale structure. Even with this unique and critical science, radio science participated in another first-time event, radar bi-static scattering observations near Titan’s north pole. I’m happy to say both major science activities were successful, along with a wonderful and leisurely stellar occultation as observed by our ultraviolet instrument. As always, science results from these various observations will follow in the weeks and months to come.

Even while scrambling with the frenetic pace of Titan encounters, the science teams took a moment to reflect on their favorite Cassini science results from 2008. We hope your favorite Cassini achievements at Saturn and its moons made our list! You can view the list here: http://saturn.jpl.nasa.gov/news/cassinifeatures/feature20090330/ and see if you concur with our choices. What a tough (but wonderful!) assignment, reflecting on some truly great scientific memories from the past year and posting them on our website. Speaking of the Cassini website, I’ll close with a brief mention of our recent Webby Award nomination! I have precious little to do with the website (other than penning this column), but, like you, I often click away and marvel at the latest adventures of our robotic buddy nearly a billion miles away. It’s easy to get buried with my engineering duties and forget how truly trailblazing this mission is. I thank the folks who keep the website so informative, cool, and inspirational, day after day. Your efforts in outreach actually moonlight as inreach—providing wonderment and awe that never fail to bring a smile to my face.