Capture Orbit Apoapsis

There was a hiatus from 5 to 12 July 2004 for solar conjunction with the Sun within 3 degrees of the line of sight, during which Cassini maintained its high-gain antenna facing Earth and the Deep Space Network uplinked sequences of 'no op' commands for periods of 5 minutes 10 to 20 times per day in order to accumulate statistics on the reliability of the uplink in such conditions. Meanwhile, the spacecraft recorded magnetospheric and plasma science observations. On 13 July Cassini emerged back into the solar wind. While the Plasma Spectrometer monitored the state of the solar wind, the Ultraviolet Imaging Spectrograph observed the auroral activity at Saturn's south pole.

By the end of July, the Sun was 20 degrees off the line of sight and the tracking by the Deep Space Network was sufficiently improved to enable the Periapsis Raise Manoeuvre to be specified on 19 August. The bipropellant propulsion system burn on 23 August lasted 51 minutes 8 seconds and increased the spacecraft's speed by 392.9 metres per second. The speed beforehand was 325 metres per second relative to the planet - a mere 1 per cent of its speed at the conclusion of the orbital insertion manoeuvre but, as with anything thrown 'up' in a gravity field, it had slowed as it climbed. The manoeuvre was designed to set up the trajectory for the fly-by of Titan on 26 October and lift the periapsis on 28 October by 300,000 kilometers in order to clear the ring system. After the 88-minute Deep Space Manoeuvre in 1998 and the 96-minute Saturn Orbit Insertion burn, this was the third most significant firing of the engine. As this was to be the last fully pressurised burn of the primary mission (subsequent firings would made in 'blowdown' mode, using the residual pressure in the propellant tanks) the latch on the helium flow was left open for 33 minutes after the burn in order to build up the pressure in the propellant tanks, then closed to isolate the system from the leaking outflow regulator. On 27 August, at apoapsis at a range of 151 planetary radii, some 9 million kilometres, Cassini headed back in on revolution 'a' of the tour designed to overcome the Huygens relay problem. On 8-9 September the Titan Atmosphere Model Workshop met at the Goddard Space Flight Center to integrate the atmospheric observations of the T0 fly-by with ground-based supporting work. On 19 October the mission critical event readiness review assessed the results of the Titan Atmosphere Model Workshop.

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