On Going to Pluto

When I was very young I remember the excitement at seeing pictures taken by Voyager 1 and Voyager 2 when they encountered Jupiter and Saturn in the late 1970s. (I don’t remember any similar excitement during the Uranus or Neptune encounters–certainly nothing mainstream.) According to this article, an encounter with Pluto was a real possibility as well.

Even though they reconfigured Voyager 2 for a Grand Tour, the mission was sold on the exploration of Jupiter and Saturn. In order for Voyager to go on to Pluto, the encounter trajectory with Saturn would have been further constrained. No close flyby of Titan, for example, would have been possible. And even then, Titan was a key target. As Charley Kohlhase recalls, “we also wanted a second crack at Titan in case Voyager 1 failed…. We would have given up the Voyager 2 Jupiter-Saturn-Uranus-Neptune for another Jupiter-Saturn (with Titan).” Ellis Miner – who worked on Cassini with me for a number of years – also commented: “as we were approaching Saturn with Voyager 2, we could have gone directly to Pluto or we could engineer encounters of Uranus and Neptune. We didn’t even know that Pluto had a moon at that time, but it wouldn’t have made any difference. The combination of Uranus and Neptune were deemed far more important than a single flyby of Pluto. If we were making that choice today, I believe the choice would be the same.”

It’s interesting. We could have had pictures of Pluto in the late 1980s, or pictures of Uranus and Neptune, but not both. The mission planners at JPL made the right choice–two planets instead of one–though there’s always the question of whether or not close-up photos of Pluto would have made a difference when the International Astronomical Union made the decision earlier this year to downgrade Pluto from planetary status.

Nevertheless, humanity will get to Pluto within the next ten years. The New Horizons probe will reach Jupiter in February, then with a gravity assist head toward Pluto for a 2015 rendezvous.

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