This albedo map of Titan from latitude 30°N to 80°S was produced by combining imagery taken by Cassini between 2 and 22 June 2004, and gave an improvement of almost a factor of 3 over terrestrial observations. As the rotation of the moon is synchronous with its orbital motion, longitude is measured westward of the centre of the Saturn-facing hemisphere.
apparent whether this was a moon 5 kilometres in size, or merely a transient clump of ring material.164,165 In studying four frames taken 40 seconds apart, 5 hours later, for a photometric study of the 'F' ring, Joseph Spitale at the University of Arizona at Tucson found another object interior to the ring; this was designated S/2004S4.
After the critical sequence for Saturn Orbit Insertion had been uplinked and stored in Cassini's solid-state recorders, it was read back to verify that it had been received correctly. As a further verification, the sequence was allowed to execute part of the set up, turning the spacecraft to the appropriate attitude, transitioning attitude control from the reaction wheels to the reaction control thruster system, and configuring the instruments. It was activated for real on 22 June, and Cassini adopted a 'quiescent' state that prohibited instrument state changes. At this point, the 70-metre antennas of the Deep Space Network began continuous coverage -which was to be maintained through Saturn Orbit Insertion to the start of solar conjunction a week later. Whereas a 'normal' command sequence is designed to take note of an anomalous situation and 'safe' the spacecraft, a 'critical' sequence is required to 'push on' as best it can with preprogrammed recovery options. Unless something were to go badly amiss, Cassini would not be actively commanded during this time, but merely monitored.
The location of the 'bow shock' where the solar wind accumulates in front of the magnetosphere varies with the strength of the solar wind which, being gusty, causes the magnetosphere to inflate and deflate. Cassini first encountered this feature some 3 million kilometres from Saturn, which was about 50 per cent further out than for the fly-by missions. The shock washed back and forth over Cassini a total of seven times over an interval of several days before the vehicle finally entered the relatively quiescent magnetospheric environment on 28 June. The Plasma Spectrometer found the outer region of the magnetosphere to be populated by solar wind plasma, but the charged particles closer in were evidently derived from the icy satellites and/or the rings.
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