Posted on Aug 11, 2008 08:10:31 PM | Saturn News | 1 Comments   

Todd Barber, Cassini Lead Propulsion Engineer (bio)   Best wishes from Pasadena, California on this fine day!  As I write the highly anticipated Enceladus flyby is underway. I was in the office this weekend trying to get caught up a bit (a weekend tradition), allowing me to hit the ground running on another busy work week.  This week holds exciting promise and scientific anticipation, though, in addition to my typical engineering duties. Over the weekend, we did two Reaction Wheel Assembly (RWA) biases to optimize the rotational speeds of these objects.  Through angular momentum changes, these wheels can turn and point the spacecraft, allowing incredible precision.  One of my tasks is to calculate how much propellant these biases use, so that's one thing I'm working on today. Speaking of propellant usage, there have been some questions about how much propellant we will use in the maneuvers around Enceladus and for the flyby itself.  As I mentioned in my prior blog entry, we were actually able to cancel our approach maneuver, OTM-163.  In addition, the next propulsive maneuver (OTM-164) is nearly two weeks off, setting up Cassini for solar conjunction and yet another Enceladus encounter (E5) in October.  OTM-164 will be rather large, however, using roughly 10 kg of bipropellant, about 6 kg of nitrogen tetroxide (oxidizer) and 4 kg of monomethylhydrazine (fuel).  For the E4 encounter itself, I don't have a propellant-usage prediction handy, but I can tell you it will be at most a few tens of grams of hydrazine (the monopropellant fuel), for yet another RWA bias. The bottom line is that we have plenty of propellant for our two-year extended mission and beyond.  Thanks for that great question, and we'll see all of you on the other side of Enceladus! Todd

Tags : Engineering, Science