Another Marathon Begins

Todd Barber, Cassini lead propulsion engineer



Hello from the flight deck of Cassini! The flight team has begun its version of a marathon, a six-month onslaught of short-period orbits, very frequent maneuvers and Titan flybys, and science extravaganzas. Our next true break won’t come until Cassini and Saturn are behind the sun as seen from Earth, but that’s not until September.

In my last column, I described the thrill of successfully swapping to B-branch thrusters in mid-March, and now that timing seems especially appropriate. There simply was no time between March and September to switch thruster branches, given the spate of Titan encounters and maneuvers facing the flight team.

Speaking of maneuvers, we had one curious event during OTM-183. A thermal sensor on the main engine started behaving erratically, Cassini’s first temperature transducer failure in over eleven years in flight. Even more curiously, the sensor managed to come back to life and read the correct value during the next main-engine maneuver, OTM-186, and it has been reading correctly ever since! This occurred early on Sunday morning, precisely two weeks prior to Easter. At any rate, there are no operational concerns for this intermittent sensor failure, and we have decided its output should not be trusted in the future. This is even more benign given that there is a back-up temperature measurement on the same engine chamber which is working fine.

On to things more scientific (for, after all, that is the ultimate purpose of Cassini), the last few weeks have been busy and productive. Our infrared, ultraviolet, and visible-light instruments teamed up to investigate a potential ring around Saturn’s icy moon, Rhea. We also used the same instruments to target Saturn’s braided F ring. Many of our science instruments picked up where they left off after the thruster swap, including visible-light monitoring of Titan clouds, observations of the bizarre plumes of Enceladus, and thermal infrared scans of Saturn’s rings from a new geometric perspective. We closed out a busy March with the Titan-51 flyby, a south polar pass dominated by ionospheric and magnetospheric observations. Even so, we managed to execute a Titan surface bi-static scattering experiment at T51 using our radio science instrument. No matter how many times we fly by Titan, it seems our scientific appetites are insatiable and can only be appeased with more Titan flybys.

I’ll close this week with the ultimate in armchair adventure travel—new Titan images and even movies for the earthbound observer, based on Cassini data. Human trips to Saturn are many decades off, but with this website (see Cassini Provides Virtual Flyover of Saturn's Moon Titan) the ringed planet’s largest satellite and Earth’s frosty twin is only a mouse click away.