Jupiter and its moons

1.11 Callisto

2 Discussion of Chapter 9: Jupiter itself

2.1 Jupiter and its missions: an update

Jupiter's visibly flattened shape is a result of the planet's rapid rotation. The flattening is not really apparent in Figure 9.1, because the terminator (the day-night boundary) is within the left-hand edge of the visible half of the globe. The flattened shape is better seen in Figure 1 below, in which the sunlit hemisphere is seen full-on.

Figure 1: A Hubble Space Telescope image of Jupiter, showing the complete sunlit hemisphere as it appeared on 5 October 1995. The arrow indicates the site where the Galileo entry probe descended below the cloud tops 63 days later.
Space Telescope Science Institute and NASA

Teach yourself planets (TYP) Table 1 lists a future mission named Europa Orbiter. Unfortunately, this has since been cancelled, after which NASA instead proposed a highly ambitious mission provisionally called Jupiter Icy Moons Orbiter for launch in 2011 at the earliest. However, this mission was also cancelled due to budgetary changes in 2005. There is now (2008) a planned mission called the Jupiter Polar Orbiter (Juno), with a proposed launch date of 2011, and a mission concept called Europa Explorer, which does not yet have a launch date. If you have Internet access and want to keep track of plans as they evolve, you can do so by selecting the Jupiter option at http://missionjuno.swri.edu/.

The latter part of Section 1.3 mentions the onward journeys of the two Voyager spacecraft towards interstellar space. By January 2003, Voyager 1 had reached over 87 AU from the Sun and Voyager 2 over 69 AU. Both spacecraft were healthy, with enough power to keep them operational until at least 2020.