<i>Originally, the spacecraft was to have an independently pointable scan platform, and wasn't it even to have a spinning section and an inertial section?</i><br /><br />No, the Cassini orbiter, even the early iterations derived from the Mariner Mark II design (CRAF/Cassini), has always been a total three-axis stabilized spacecraft. Note that the Mariner Mark II designs had <i>two</i> scan platforms on deployable booms that were baselined for each spacecraft: a high-precision <i>scan</i> platform and a low-precision <i>pointing</i> platform (on Cassini, the latter was to be replaced by a turntable and a ram-direction platform). As you alluded to, the scan platforms were eliminated for cost and complexity reasons, as was the proposed steerable medium gain antenna (MGA) proposed for Cassini, which would have also relayed data from Huygens. This task will now be done through the Huygens radio relay hardware mounted on Cassini's high gain antenna (HGA).