Much had been learned from the process by which the Galileo spacecraft's orbits of Jupiter had been planned on a just-in-time basis.68 In the case of the Jovian system, there were four moons sufficiently massive for gravity-assists to enable a spacecraft to contrive an evolving trajectory for a specific orbital tour. Cassini would be able to use only Titan. An early decision was to set up a fly-by of the enigmatic outer moon Phoebe on the way into the system. For the 1997 launch window, this required the spacecraft to perform its Saturn Orbit Insertion manoeuvre on 1 July 2004.
Given the number of mission-critical events concentrated in the post-arrival part of the primary mission, the first 15 months of all 'serious' orbital tour options were the same. The Saturn Orbit Insertion burn was to put Cassini into a highly elliptical 'capture orbit' so that when the spacecraft was near apoapsis, about 3 months later, it could lift its periapsis above its initial point of closest approach to Saturn. On the inbound leg of this orbit, Cassini would have to refine its trajectory so that when it
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