The Grand Tour, A proposal that ended with Voyager 1 & 2 Options

[Guest_Myran_*]

Seeing descriptions and even images of old projects that never did get underway, my memory was stimulated into remember 'The grand tour' plans.

Back in the 1960 the proposal was to fly no less than 4 spacecrafts, each with atmospheric probes for the four gas giants and one even with a flyby of Pluto after swinging past Jupiter and Uranus.

The proposal for this project did fare the same way as many other ambitious plans, that of limited funding but it was skillfuly advocated and eventually ended up with the dual Voyagers (which btw originally only was planned for flyby's of Jupiter and Saturn).

Regardless, if anyone remember some tidbits or even sits on more specific information I would be happy to have my memory refreshed. Thank you in advance!

[Guest_BruceMoomaw_*]

You may be right -- but one of them could certainly have been retargeted to Pluto.

[tedstryk]

You may be right -- but one of them could certainly have been retargeted to Pluto.

The choice had to be made...Send Voyager 1 on to Pluto or have a close Titan flyby. The Titan flyby, thanks to the clouds, was largely a bust, so in 20/20 hindsight, it is a shame it didn't go on to Pluto.

[JRehling]

The choice had to be made...Send Voyager 1 on to Pluto or have a close Titan flyby.  The Titan flyby, thanks to the clouds, was largely a bust, so in 20/20 hindsight, it is a shame it didn't go on to Pluto.

I don't think Voyager 1 @ Titan was a bust. It provided radio occultation data that pegged the surface temperature and pressure so accurately that Huygens scarcely improved the measurement -- THAT is saying something. (I'm sure Huygens shrank the error bars...) That occultation also pegged the mean molecular weight. And Voyager images of Titan in the orange filter DID show surface features, though that fact was recognized only 15 years later.

It is subject to debate if the same information could have been had using later stellar occultations. The key question would be if Cassini/Huygens design was improved in any way owing to the Voyager 1 pass -- could be a PhD thesis to try to shake that out. Extra credit for assessing whether V1's probing of the bow shock would have been altered in the other plan.

Taking the counterfactual too literally, we could say that with Cassini there now, we would have all of the Voyager 1 discoveries in our pocket by today's date anyway, so in a sense, we got nothing from it that we wouldn't have had by 2005, and could only have gained by swapping it for Pluto. Then again, New Horizons would not have been approved if we'd had a Voyager flyby of Pluto, and NH certainly has a superior instrument payload thanks to 28 years of technical improvements. So come 2015, it may be said that *Pluto* science owes a lot to Voyager 1 not having flown by it!

[ljk4-1]

I don't think Voyager 1 @ Titan was a bust. It provided radio occultation data that pegged the surface temperature and pressure so accurately that Huygens scarcely improved the measurement -- THAT is saying something. (I'm sure Huygens shrank the error bars...) That occultation also pegged the mean molecular weight. And Voyager images of Titan in the orange filter DID show surface features, though that fact was recognized only 15 years later.

It is subject to debate if the same information could have been had using later stellar occultations. The key question would be if Cassini/Huygens design was improved in any way owing to the Voyager 1 pass -- could be a PhD thesis to try to shake that out. Extra credit for assessing whether V1's probing of the bow shock would have been altered in the other plan.

Taking the counterfactual too literally, we could say that with Cassini there now, we would have all of the Voyager 1 discoveries in our pocket by today's date anyway, so in a sense, we got nothing from it that we wouldn't have had by 2005, and could only have gained by swapping it for Pluto. Then again, New Horizons would not have been approved if we'd had a Voyager flyby of Pluto, and NH certainly has a superior instrument payload thanks to 28 years of technical improvements. So come 2015, it may be said that *Pluto* science owes a lot to Voyager 1 not having flown by it!

Are those surface images of Titan from Voyager 1 available somewhere? I can't recall ever seeing them before, just the big fuzzy orange tennis ball ones.

What do folks here think of the assessment that Voyager 2's exploration of Triton in 1989 was equivalent to a flyby of Pluto?

[JRehling]

Are those surface images of Titan from Voyager 1 available somewhere?  I can't recall ever seeing them before, just the big fuzzy orange tennis ball ones.

What do folks here think of the assessment that Voyager 2's exploration of Triton in 1989 was equivalent to a flyby of Pluto?

The Titan-from-Voyager work is here. That includes some best-yet looks at the northern latitudes! Add 'em to the map!

http://www.lpl.arizona.edu/~jrich/vgertitan.html

A close look at Triton is in no way equivalent to a Pluto flyby. The two worlds appear to be very similar in bulk composition, but the same could be said of Venus and Earth. Admittedly, no one would expect the two to turn out to be as different as Venus and Earth, but we won't know until we see Pluto.

Pluto should experience harsh seasons and some level of atmosphere freeze-out, while Triton (most latitudes, anyway) maintains more constant illumination from a very constant distance from the Sun. Pluto is in stationary lock with little Chiron while Triton faces tides from massive Neptune. And even without those two things, the worlds may have evolved differently for other reasons.

We don't know enough about Pluto to know how similar the two worlds might be, but for now, we have to assume that there are significant differences. Of course, they're liable to be more like one another than either of them is like some other randomly-chosen world...

[Bob Shaw]

The Voyager Titan surface images are remarkable! It's astonishing that after a quarter of a century the old data can still reveal so much (though we've seen elsewhere on the board that Surveyor, Mariner 69 and the Phobos mission all had many hidden gems, too - not to mention the super-resolution Viking views, or the Pioneer Io image). I suppose this shows the true value of properly archived data, and the false economy of disposal. I don't especially rate the 'Pioneer Anomaly' argument, but these Titan pictures certainly do show that a scientific consensus can shift over time, and that the new paradigm can make effective use of old data.

So: Let's hear it for saving the data, folks!

And: Let's spread the word of these happy outcomes!