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Posted by: Myran Aug 21 2005, 06:37 PM

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!

Posted by: BruceMoomaw Aug 21 2005, 08:47 PM

There was a nice detailed article on it -- and its demise -- in the Journal of the British Interplanetary Society about 7 years back. I have a photocopy, and will reread it to refresh my memory. (I don't recall it including atmospheric entry probes, though.)

Two of the craft would have been launched in 1977 to fly by Jupiter, Saturn and Pluto; the other two in 1979 to fly by Jupiter, Uranus and Neptune (thus both stretching out the financing and allowing avoidance of the Saturn-to-Uranus trajectory, which was thought to brush dangerously close to the outer edge of Saturn's rings). The craft would hve been distinctly more complex than the final Voyagers to ensure long lifetimes -- including, in particular, computers with triple components each of which would take a majority vote on their decisions.

Even after GT's 1972 cancellation and replacement by Mariner Jupiter/Saturn (renamed "Voyager" in 1977), NASA had a fallback plan: launch the third, backup Voyager by itself to Jupiter and Uranus (with an extended mission to neptune if it was still working) in 1979. "Mariner Jupiter/Uranus", as it was then called, would have had minor modifications: a set of reaction flywheels to allow it to slew around faster and more accurately to rapidly observe different targets during its fight through the Uranian system; replacement of its vidicon cameras by CCD cameras with near-IR sensitivity; and replacement of the IR spectrometer by one with greater sensitivity to longer wavelengths to examine the cold outer planets better. But that, too, got the axe in 1975, simply because of the never-ending funding demands of the Space Shuttle -- plus the fact that NASA wanted no extension of the expendable rocket program into 1979, which is the same reason they vetoed all proposals to launch Galileo on a Titan booster in 1982. They had a really major fraud to perpetrate on the taxpayers, after all, and any slipup like that could have bollixed it. So Voyager 3 hangs on the Air & Space Museum wall instead (near the third Viking lander and the backup to Mariner 10).

Had Voyager 3 been flown, I think it very likely NASA would also have extended Voyager 2's mission to proceed on from Saturn to Pluto -- which it would have reached a month or two before Voyager 3 reached Neptune, thus getting a good look at that planet when it was near both perihelion and equinox to provide the best possible scientific view of it (and also allowing Clyde Tombaugh to get a closeup look at the planet he had discovered). No such luck.

Posted by: tedstryk Aug 21 2005, 11:26 PM

I don't think that was possible. It was Voyager 1 that could have been retargeted to Pluto.

Posted by: BruceMoomaw Aug 21 2005, 11:41 PM

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

Posted by: tedstryk Aug 22 2005, 12:14 AM

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.

Posted by: JRehling Aug 22 2005, 02:51 AM

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!

Posted by: edstrick Aug 22 2005, 07:02 AM

The Voyager 1 Titan flyby was enormously successful. The surface radius was established, the atmosphere structure was determined with such precision that the Huygens probe was possible. Atmosphere composition and haze physical properties were determined with considerable precision. Before Voyager, it was unknown whether there was a significant greenhouse effect, or whether the surface was only 0.1 atmosphere pressure with a temperature of around 80 K.. essentially at the tropopause. Some of this would have been determined by Earthbased observations in the 2+ decades since Voyager, but a lot would not have been.

The only investigation that was a "bust" was surface geology investigation.. but.. then, that was a "bust" too for Jupiter, Saturn, Uranus, and Neptune!

Posted by: Myran Aug 22 2005, 07:15 AM

Thank you BruceMoomaw for your reply.
Yes I distictly remember it was supposed to be four probes, and not two which is said on some sources like Wikipedia. For the number of only two I think theres some confusion with the dual Pioneers that also was a spinoff of sorts from the early Grand Tour proposals. But in the end it was the Voyagers that carried out the plan and did so very well, getting us a clear look at the moons of Jupiter and Saturn but also the only clear views of Uranus and Neptune that I will ever get.
But I agree its a pity we did miss out on Pluto, the opportunity was there. It will be a close call for me with New Horizons in 2015, lets try!

Regardless, I do remember a plan that involved cone shaped atmospheric probes in regard with the first four probe plan, and I remember that one well since it had a graph. But that proposal might not have been one AMES or JPL proposal at all but originated somewhere else like at some university. After 40 years things in my memory tend to blend somewhat.

Posted by: dvandorn Aug 22 2005, 07:32 AM

Exactly -- each mission does, indeed, build upon what we learned from the last one. Without the Pioneers, we might not have designed the Voyagers to properly withstand the radiation environments at Jupiter and Saturn. Without the Voyagers, we wouldn't have had nearly as good an idea of which instruments would give us the best scientific return from Cassini. (For example, had we not done the Titan flyby during Voyager 1, we might not have included RADAR on Cassini.)

My memory of the whole Grand Tour concept is that, sometime in 1968 or 1969, I saw a proposed plan for two Grand Tour spacecraft that would require Saturn V boosters. They would take advantage of the late-70s launch windows to send both spacecraft to each of the outer planets in turn, with entry probes for the gas giants and, IIRC, a Titan hard-lander.

When NASA decided to shut down the Saturn V production line in late 1969, the people at JPL proposing the Grand Tour mission took it rather poorly, insisting it was total madness to pass up an opportunity like this. They made some enemies at other NASA centers with their vehemence. For a while, no plans for late-70's outer Solar System exploration were allowed to have the words "Grand Tour" in them -- it got that bad.

Pioneers 10 and 11 were already in the pipeline, and a follow-on mission, consisting of similar Jupiter/Saturn flybys *only*, was being developed that later became the twin Voyagers. But during the process of designing the Voyager missions, the Grand Tour aspects were played WAY down. It was as if the JPL teams were told that bringing up Grand Tour was a good way to kill the Jupiter/Saturn flybys. But, at the same time, they designed both spacecraft with enough power and maneuvering gas to handle the full Grand Tour -- with a little bit of luck.

So, at least the way I remember it, we got almost all of our Grand Tour mission by selling it as *only* a set of Jupiter/Saturn probes, and sneakily adding the Uranus and Neptuine encounters only after the spacecraft were in flight. Even though the Grand Tour was implicitly designed-for during spacecraft and mission development, it was simply not discussed in detail for fear that those who thought they had "killed that Grand Tour nonsense" wouldn't notice until it was too late...

-the other Doug

Posted by: BruceMoomaw Aug 22 2005, 08:26 AM

The article I was after is D. Rubashkin's "Who Killed the Grand Tour? A Case Study in the Politics of Funding Expensive Space Science", in JBIS, Vol. 50, pg. 177 (year 1997). Unfortunately, it isn't available on the Web.

The short version is that Grand Tour was like Rodney Dangerfield -- at the time, it got shockingly little respect from ANYBODY. The Space Studies Board (aka COMPLEX) took a surprisingly dim view of it (as compared to the intensive exploration of Jupiter alone), and in fact recommended it be flown only if NASA's space science budget got a 50% hike for the rest of the decade -- which everyone knew wouldn't happen. Sen. Clinton Anderson of NM (then chairman of the Senate Aeronautical and Space Sciences Committee) took a very dim view of it because it was bleeding off funds from the NERVA nuclear rocket program, which he fiercely defended because Los Alamos was associated with it; no other member of Congresss seems to have any fondness for it; and Pres. Nixon had no intention of funding anything that would interfere with the Space Shuttle's development.

Anderson used the idea that NERVA and other nuclear rockets might allow space probes to be launched DIRECTLY to the three outer planets to bash Grand Tour mercilessly in 1971. By mid-1971 GT was already virtually moribund (and NASA had already dropped its plans to launch a preliminary test of the craft in 1975 that would fly by Jupiter and then go sharply out of the ecliptic, and had also delayed the launch of the first of the two Jupiter-Saturn-Pluto craft, which was originally supposed to fly in 1976 instead of 1977).

The last straw came in October 1971, when Nixon decided that in order to properly fund Shuttle he had to cancel either Apollo 16 and 17 (which he initially leaned toward doing), or GT (which NASA and COMPLEX persuaded him to do instead). At the same time, ironically, the White House zapped NERVA, briefly mollifying Sen. Anderson (who retired only a year later) with a smaller nuclear propulsion program which they also cancelled as soon as he was safely gone. The moment GT was cancelled in Dec. 1971, however, NASA and the White House replaced it with Mariner Jupiter/Saturn, which by contrast everyone -- COMPLEX, the White House and Congress -- immediately and enthusiastically endorsed, largely because it would cost less than half as much. (NASA still hoped from the start to fly at least one such craft to Uranus and Neptune, but without the "Self-Test And Repair" computer that was a major feature of the GT craft.)

The article doesn't say anything about the sequel to this story: NASA's brief hopes of flying Mariner Jupiter/Uranus in 1979. I'll do a bit more digging on that subject, but the main story is very simple: as with so much else, the Shuttle ate it. (And I have still seen no sign that GT was intended to carry any entry probes -- indeed, I very clearly remember that the detailed description of the GT craft in "Astronautics and Aeronautics" magazine at the same time included no mention of any entry probes.)

Posted by: edstrick Aug 22 2005, 08:41 AM

The vehicle for grand tour was for a while at least known as "TOPS": The Outer Planets Spacecraft. Bruce: There was a substantial article in either Space Aeronautics or Astronautics and Aeronautics on the proposed mission in the 1970-71 time frame. I can't get at my brother's copies now to find and ID it.

The de-scoping of the mission also had the effect of descoping the instruments to Mariner Jupiter Saturn requirements. Their sensativities in many respects at Uranus / Neptune were crummy compared to what would have been flown <bigger apertures, etc> on TOPS.

The real loss, of course, was the third spacecraft. We, also of course, were lucky. Both Voyagers survived their primary mission and into extended missions. If Voyager 1 had failed to do it's required science at Titan and the critical ring radio occultations, Voyager 2 would have recovered those observations and there would have been no Uranus-Neptune mission.

Posted by: Bob Shaw Aug 22 2005, 10:10 AM

I thought TOPS was Thermo-electric Outer Planetary Spacecraft?

Posted by: Myran Aug 22 2005, 12:01 PM

Thank you dvandorn, you nailed it there. The timeframe of 1968 or 69 is just about right, since my recollection of the proposal fits with other memories from my personal life of that time.

The four probe proposal had blended in my memory with the two probe one.
I think so since you stated one thing I failed to mention, that the proposal included the option to have one atmospheric probe swapped for a Titan lander. So you did indeed remember correctly.

BruceMoomaw set the record straight for me, yes somehow I must have had the Mariner Jupiter/Uranus proposal in the back of my head when I wrote the original post. But also brought up another tidbit for my original interest for the Grand Tour and that was the 'Self-Test and repair' ability plus the other autonomous abilities they would have been given. If they had flown they would have been true robotic ambassadors for the human race.

Posted by: edstrick Aug 22 2005, 12:08 PM

Mariner Jupiter/Uranus was sunk by both the Shuttle, and as I recall, by the Ford Administration's utter indifference. Remember "WIN: Whip Inflation Now" buttons?

The shuttle... and Jimmy Carter sunk the Hally's Comet Rendezvous mission when they refused to fund development of SEPS.. the solar-electric propulsion system and flight test it so it'd be mature technology for a major solar electric system that could do a Hally rendezvous.

One of many reasons I regret being stupid enough to vote for "Malaise Jimmy".. I wanted something better than "King Log" and voted for "King Stork" ......

Posted by: BruceMoomaw Aug 22 2005, 12:52 PM

You may rest assured that either one of them would have been suckered by the Shuttle; I doubt there would have been any significant difference in their space policies.

That article you're thinking of was definitely in "Astronautics and Aeronautics"; I read it at the time, although I can't quite remember whether it was in 1970 or 1971.

Regarding Mariner Jupiter/Uranus' instrumentation: I mentioned that it would have carried both CCD cameras and an improved version of the IRIS spectrometer of its two predecessors. NASA made a considerable effort to get a copy of the latter ("MIRIS") onto Voyager 2, given its hoped-for Uranus and Neptune flybys; but in the end they weren't quite able to qualify it in time.

As for Voyager 1's close Titan flyby: there was absolutely no question that it was worth attempting, even if you had to give up an optional Pluto flyby in the process. Quite apart from the far better (and crucial) atmospheric data obtained from such a close flyby, before the flyby there was a good chance that Titan's atmosphere and clouds would be thin enough to provide a view of the surface -- in fact, chief camera PI Bradford Smith bet that such would be the case.

One thing that has always puzzled me is why no attempt was made to have Pioneer 11 do a Titan occultation, since that could have been done even at a long range -- after all, Pioneer 10 did it for Io. Apparently there was no way to combine it with the proper trajectory for a rehearsal of Voyager 2's close brush past the rings, but I don't know the details.

Posted by: Bob Shaw Aug 22 2005, 12:59 PM

Hmmm... ...an outer planetary mission with a self-testing and repairing computer system aboard. Sounds fine until the AE35 unit enters a predicted failure mode.

'OK, STAR, let's take those pictures!'
'Shan't. Won't. Can't make me. N'yahh, n'yahh, n'yahh!'

Posted by: Myran Aug 22 2005, 02:43 PM

Hehe! I see that Bob Shaw have seen the 2001 movie. (Yes me too.)

In reality it wouldnt be such a bad thing to have, not even for our MER rovers. Remember when Spirit was brought to a complete standstill due to one overfilled flash memory. So self test, diagnostics and automatic correction/repair is something that still could save the operators from sleepless nights.

Posted by: Bob Shaw Aug 22 2005, 03:15 PM

Myran:

They said that about XP!

Bob Shaw

Posted by: Analyst Aug 22 2005, 06:24 PM

Besides the paper „Who killed the Grand Tour?“ published in JBIS the following monograph gives a good overview of the Voyager program from a management point of view. You can compare it with SS’s recent book about the MER missions. It starts with the program genesis and hurdles and continues to building and lauching the spacecraft. The important resuls from the flybys are given and some facts about the current interstellar mission.

“Voyager’s grand tour: to the outer planets and beyond“
by Henry C. Dethloff and Ronald A. Schorn
ISBN 1-58834-124-0

Highly recommended. Read this and SS’s book and you know what roadmaps and long term plans are for.

Analyst

Posted by: ljk4-1 Aug 22 2005, 07:44 PM

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?

Posted by: tedstryk Aug 22 2005, 08:03 PM

I know that at the time of the Titan encounter, Pioneer's communications with earth were so disrupted by the fact that it was almost in solar conjunction that a lot of data was lost. So perhaps they figured they wouldn't have a good enough signal to make it worth it.

Posted by: Bob Shaw Aug 22 2005, 08:05 PM

On the first point, yes, I'm also fascinated to hear that some surface features may have been visible - that's news to me!

And as for Triton, it may be the yardstick by which we judge Pluto, so it certainly was worthwhile having a good hard look at!

Posted by: edstrick Aug 22 2005, 08:18 PM

Pioneer's Saturn flyby was "forced" onto a trajectory that took them through the ring-plane at the approximate radius where Voyager 2 would have to cross to go on to Uranus and beyond. The actual trajectory crossed the ringplane inbound, reached periapsis literally under the ring-plane, and crossed the ringplane outbound at a similar radius as the inbound crossing.

Encounter was only about a week before conjunction, and communications rapidly deteroriated after Saturn, but they didn't lose that much data, they did have to cut data-rates, especially outbound.

The alternate trajectory being considered was "inside" the rings, through the ringplane close to Saturn's equator...through part of the "D" ring. Given that a "D" ring had been claimed and named, even if it was highly debatable, it was not at all clear what Pioneer's chance of survival were. The science on the outside rings crossing was nearly as good, except for gravity studies of Saturn. Given the importance of verifying the survivability of the Voyager trajectory, the recommendation was the outside crossing.

Titan was "behind" Saturn and in a really poor location for any possible encounter. On the departure trajectory, they got low resolution full disk images that weren't much better than Earthbased images at the time, but they did see the north/south brightness assymetrys... opposite (I think) to what Voyager saw, which indicated seasonal or meteorological effects. The infrared radiometer got very rough thermal measurements on the (for it) unresolved disk which crudely supported "weak or no greenhouse" models of the atmosphere.

Posted by: JRehling Aug 22 2005, 08:54 PM

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...

Posted by: Bob Shaw Aug 22 2005, 09:31 PM

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!

Posted by: BruceMoomaw Aug 22 2005, 11:47 PM

Ah. I had forgotten that Pioneer 11 flew through the ring plane at Voyager 2's planned distance TWICE (which I preseume was intended as an additional check on the rings' safety) -- which would have slapped far more limits on its trajectory than a single ringplane pass at that distance. I did know about the alternative plan to fly through the D Ring, which almost all the scientists backed but which NASA HQ vetoed (correctly, I think) because of the need to check the safety of Voyager 2's extension to Uranus. (By the way, brief consideration was given to extending Pioneer 11 on to a Uranus flyby, although it was quickly rejected and I don't know the details.)

As for Triton being an acceptable substitute for Pluto: no way. Triton, having been initially captured into a highly elliptical orbit around Neptune, then underwent really massive tidal heating while its orbit was being circularized -- heating intense enough that it's thought likely that ALL its ice melted into liquid, producing massive chemical changes as well as erasing its original physical structure. And, indeed, both chemically and in terms of their albedo patterns, Triton and Pluto bear little resemblance. If you want a reliable look at a KBO in its original form, the New Horizons mission is a necessity.

Posted by: ljk4-1 Aug 23 2005, 01:19 PM

The famous August, 1970 issue of National Geographic Magazine depicts the flyby routes of the two probes meant for the Grand Tour, plus it contains a fictional ship's log of what those probes and others then planned for the coming decades were believed to find as they journeyed through the Sol system.

http://solareclipsewebpages.users.btopenworld.com/SECalendar_files/NATIONALGEOGRAPHIC.htm

Posted by: tedstryk Aug 23 2005, 03:57 PM

When I made that comment, I was mixing it up with Pioneer 11 where the data return was messed up by solar conjuction. Sorry, I am scatterbrained. It is a shame Pioneer 11 wasn't sent on to Uranus and or Neptune. It could have been, but it wasn't thought that it would survive long enough, plus the Voyager team was first-hungry. While I am not sure if it could have imaged such dark worlds as all, a second pass through their magnetospheres and occultation data would have no doubt been helpful.

Posted by: gndonald Sep 21 2013, 10:35 AM

Apologies for bumping a really old thread, but I have managed to locate the report into the Thermo-Electric Outer Planets Spacecraft from which I've managed to copy the attached images.

Interstingly the report claims that the only spacecraft built was going to be ground test model to develop technology for the coming Grand Tour.

A link to the report (155mb) is below.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19730012834_1973012834.pdf