Cassini Equinox Mission Set to Begin
The Cassini Project Science Group (PSG) meeting #45 is taking place this week in Rome. Because of the large European participation in the international Cassini-Huygens mission, every third PSG meeting is hosted by a European participant in Cassini. The 4-year Cassini prime mission officially ends at at the end of the month, and a two-year extension to the mission begins the next day. Because a highlight of this extended mission is to take Cassini through equinox at Saturn, when the Sun is in the plane of Saturn’s rings, this is officially known as the Cassini Equinox Mission (CEM). The CEM was recently officially approved by NASA headquarters through September 30, 2010. The CEM does not end with the demise of Cassini. It will still be orbiting Saturn on October 1, 2010. Because there are planetary protection issues at Saturn (a requirement to avoid any possible biological contamination of potential abodes of life in the Saturn system), the spacecraft will ultimately be disposed of, probably by crashing it into Saturn. So there will be some sort of extension beyond the end of the CEM. Hopefully this will include further scientific study of the Saturn system, as there will be much more to learn after the end of the CEM. In large part this is due to the long seasons at Saturn, but there are also dynamical phenomena in the rings that operate on timescales of many years. An extension of Cassini beyond the CEM will enable us to study these phenomena as well as perhaps studying the atmospheres of Saturn and Titan until the northern summer solstice. This would show us the lakes region at the north pole of Titan and show if they change over the course of the seasons.
This image of the F ring shows two narrow components, a structure also seen in recent stellar occultations and significantly different than the appearance of the F ring in earlier Cassini images as well as from Voyager, highlighting changes in the rings over the course of decadal timescales.