The Frenzy of 16-day Orbits

Todd J. Barber, Cassini lead propulsion engineer

In my continuing effort to get caught up, I will attempt to cover an "April shower" of science observations and engineering activities from the ringed gem, Saturn. Cassini sailed right through tax day in the U.S., only taxing our ability to keep up with its torrent of science.

From the engineering side of the project, we were able to cancel OTM-190. Even in the brief window between OTM-190 and the Titan-53 flyby, we did some nifty fields and particles science with the Cassini plasma spectrometer and magnetospheric instruments, studying Saturn's magnetosphere at local dusk. We also turned our ultraviolet camera, UVIS, to Spica, the brighest star in Virgo. This is a handy reference star, just as it is here on Earth for amateur astronomers looking to gaze out of the plane of the Milky Way to countless galaxies that lie beyond.

Titan-53 occurred at relatively high altitude (3,600 kilometers, or 2,237 miles), but this made it no less interesting for our voracious scientific appetites. It was time for UVIS to shine for this flyby; rather, I guess more literally, it was the sun's turn to shine through the Titan atmosphere as UVIS looked on attentively. This allowed for the determination of atmospheric nitrogen levels between 900-2,300 kilometers above Titan, a gas most familiar to denizens of the third rock. Not content with this gander to the nearest star, a more distant stellar target was also observed as it winked from view -- very slowly -- as the Titan atmosphere occulted this distant sun. This leisurely occultation enabled excellent data collection about the haze and hydrocarbon chemistry in the region 300-1,600 kilometers above Titan. In concert with other science instruments and additional Titan flybys, the secrets of this mystery moon will eventually be revealed.

Cassini closed out April with yet another maneuver cancellation (OTM-191), an RWA friction test, Composite Infrared Spectrometer (CIRS) temperature mapping of Saturn's rings, dynamic movies of F-ring streamers by the visible light camera, and a final planned attempt to image potential rings around Saturn's icy satellite, Rhea. There's truly never a dull moment within the frenzy of 16-day orbits!