About the Author Slides from the Lecture Presidential Lecture 1992 - James A. Van Allen

Figure 9. The trajectories of the four outer-solar-system spacecraft Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2 as projected on the ecliptic plane. The dates of planetary encounters are shown. Tick marks along each trajectory are at one-year intervals. All four spacecraft are now in hyperbolic solar-system-escape trajectories.


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