On this page, I found what I’ve been looking for over the past week or so: information on where the Voyager and Pioneer spacecraft are right now.
But, looking at the neato graphs, I see that Voyagers 1 and 2, as well as Pioneer 11, are all heading one way, generally, as they speed out of the solar system.
Pioneer 10, on the other hand, is going pretty much the opposite way than the others. Why is that?
Just a WAG, but weren’t they all primarily visiting various planets, and were just left moving in whatever direction they happened to end up going?
Certainly NASA knew they were going to continue outward, but I don’t recall any particular reason for choosing a direction.
Well, crapola!
I had written a lengthy (and clever!) answer to this query which even included a reference to Ken Kesey’s One Flew Over the Cuckoo’s Nest. (“One flew east, and one flew west, and …”) when AOL logged me off due to “inactivity”. Apparently witty remarks and astrophysical wisdom doesn’t count as activity.
Then when I log back on rjk has already answered with essentially the same answer as mine, i.e.: just luck.
I can’t reconstruct all of my previous reasoning (well, guessing, actually) but the short answer is that these long-distance probes typically use Jupiter as a gravitational slingshot to boost them on their way. If you pass to the “right” of Jupiter you get slung off to the “left” and vice versa. For some reason the two Pioneer probes were directed on opposite sides of the planet.
The fact that the two Voyager probes are on about the same path is because they passed on the same side at about the same time. The fact that one of the Pioneer probes is on the same path is, IMHO, pure luck. The possible configurations of the probes and the planets is theoretically infinite and it’s surprising that two different programs, years apart, end up in the same place.
Sorry to hear it, pluto! I’m sure your reply would have been far more readable than mine. (This one was funnier, too! 
)
Voyager 1 & Voyager 2 were launched at about the same time (NASA used to do everything in pairs) for more or less the same mission. So, they followed similar paths. IIRC, Voyager 1 did a close fly by of either Saturn or one of its moons, thereby sending it “up” out of the plane of the solar system. Voyager 2 kept within the plane of the solar system and when on to see Uranus & Neptune. You can see in that second picture that V1 and V2 are going in different directions now.
I’d have to check into the Pioneer info.
Here’s a helpful link for the status of NASA’s spaceprobes…
http://spacelink.msfc.nasa.gov/NASA.News/Where.Are.They.Now/.index.html
Voyager 1 was sacrificed in order to do a close flyby of Titan, Saturn’s largest moon, and the moon with the thickest atmosphere in the solar system. Unfortunately it turned out that Titan’s atmosphere was even thicker than anyone had guessed and all we saw was a fuzzy orange blob, no breaks in the clouds to get a peak at the surface…which might be a liquid ocean of various carbon compounds.
Can’t help on why P10 is going such a different direction from P11. They were launched at Jupiter at basically the same time…I guess the glib answer is that P10 took a left turn at Jupiter while P11 took a right turn in order to reach Saturn.
NASA seems to be cursed with Titan. The Cassini probe is going to drop a probe into Titan, but unfortunately they just realized that the Titan probe will likely not be able to keep in radio lock with Cassini. Luckily they still have three plus years to come up with a solution on the fly.
Here’s a link to basic mission descriptions of Pioneer 10 and 11. It doesn’t say why, but it does indicate that 11 went on to give us our first good views of Saturn whereas 10 just went on its way. It may have been that the relative positions of Jupiter and Saturn were more favorable at the time of 11’s visit (364 days after 10) for a slingshot in that direction, whereas it wouldn’t have worked as well for 10 so they just let it keep on truckin’ in the direction it was generally headed.