A Momentous Anniversary and the Tradition Continues

Todd J. Barber, Cassini lead propulsion engineer

As Cassini continues its intricate orbital ballet at Saturn, its home institution, the Jet Propulsion Laboratory in Pasadena, CA, is celebrating a momentous anniversary. As I write this, exactly 50 years ago today JPL's Explorer 1 pierced the Florida night sky just before local midnight. America's first orbital triumph a few months after Sputnik 1 and 2 heralded a new direction for JPL and ushered in a space race fueled by a cold war. The scientific legacy of Explorer still echoes through decades of space science, particularly the discovery of Earth's Van Allen radiation belts. Thus began a never-ending tradition of stunning surprises in the alluring field of space science, a tradition that continues to this day with flagship missions such as Cassini-Huygens.

After a jam-packed maneuver schedule and slew of 16-day orbits at the end of 2007, Cassini is now making a relatively leisurely set of elliptical loops of the ringed planet. Even though we're currently executing 12-day orbits, our last Titan encounter was over three weeks ago, and we're about at the high point (apochrone) of this particular 12-day orbit of Saturn. Since Titan has an orbital period of about 16 days, this second-largest moon in the solar system will encircle Saturn three times before our next Titan encounter, T41 on February 22, 2008. I think as a propulsion engineer I'm most excited about an impending main-engine maneuver for Cassini, scheduled for Feb. 5, 2008. This marathon four-minute burn will change the spacecraft speed by about 37 meters per second (or 83 mph). This may not seem like much given the typical orbital speeds for our robotic explorer, but this actually will be the largest Cassini burn in nearly three-and-a-half years!

Like many of you, perhaps, I struggle to keep up with the continuous outpouring of new Cassini science results. I might suggest if you haven't visited the Cassini main website lately (which is unlikely if you're reading this column, I realize!) that you take a few moments to do so. With the wonderful engineering challenges and opportunities in flying this mission, the vast majority of my science edification comes from viewing the website, just like you. I was tickled with a brief excursion into cyberspace today, reading about Cassini's latest results for the wispy, icy moon Rhea, radar images from Titan's south pole during the T39 flyby in late December, and in particular a knotty F-ring image that knocked me out. If ever I grow complacent about my job as an engineer on this project, one swift visit to the Cassini website reminds me of the passion that brought me to Southern California and JPL, fifty years in the satellite and spacecraft business and counting.