Mariner Mars 1964, Mariners 3 and 4 to Mars: imaging plans? Options

[Phil Stooke]

I am currently working on a book about lunar exploration, but looking ahead to the next one, which will cover Mars. One question to which I think I have an answer - but I'd like to see what my fellow Mars enthusiasts think - is this:

Mariner 3 failed to leave Earth. But if it had flown successfully, what area on Mars would it have photographed?

My understanding is that there was no specific plan. The MM64 press kit, for instance, says nothing about image coverage for either Mariner 3 or Mariner 4. I believe that navigation to planetary distances was still so uncertain that the flight team could not predict at launch the sub-spacecraft point at closest approach - uncertainties included the exact time of the flyby, the distance and the point at which the spacecraft would pass through the target plane. These things would be known closer to the flyby but they weren't precisely predictable at launch, so Mariner 3 never got to the stage of having an imaging plan.

Am I right?

Phil

[Guest_BruceMoomaw_*]

The scheme was more complex than that. It did involve launching Pioneer 5 toward Venus in early June 1959, but without a midcourse correction motor no one thought it would get anywhere close. HOWEVER: it also involved simultaneously launching the very first of the much bigger Atlas-Able Pioneer orbiters to Venus -- and since that had two restartable hydrazine motors sticking out of its poles, the plan really would been to make an honest effort to put it into Venus orbit. Aviation Week had several short items on it in 1959 -- and the NY Times of (I believe) May 1, 1959 made the plan's last-minute cancellation its front-page headline. (It was cancelled on the grounds that "the science payload could not be gotten ready in time", by which NASA may have meant the entire spacecraft.)

A second Pioneer orbiter was to be built simultaneously to be put into lunar orbit later. I've wasted a little time trying to find out what the exact science payload of the Venus version would have been, and all I've been able to find is one short paragraph in a 1959 aerospace magazine quoting a Democratic Louisiana Congressman briefly describing its payload on "Meet the Press" in a way that suggests it would have been identical to the payload on the lunar Atlas-Able orbiter -- that is, a bunch of fields and particles instruments plus a spin-scan IR photometer that could build up images (in this case, presumably a temperature map of Venus' cloud cover). No mention of a UV photometer, which would seem to be a natural for such a mission -- but such an orbiter could have given us radio occultations of the atmosphere.

I first heard about this plan all the way back in 1965, when I was 11 years old. (It was mentioned briefly in a back issue of "Sky and Telescope".) But finding information on it is like looking for an Upsidaisium mine -- you just find tiny crumbs here and there (including one brief mention in the June 1959 "American Mercury", H.L. Mencken's magazine which by then had been bought by a bunch of rabid right-wing anti-Semites who used to refer to "the Jewish termites gnawing at the Cross"). I finally found, in an early 1990s issue of the Proceedings of the National Academy of Sciences, a long historical reminiscence by a fields and particles scientist mentioning some of the instruments he'd put on these Atlas-Able orbiters, and I eagerly asked him for the Straight Dope -- only to be told that even HE had never heard of the Venus plan!

Anyway, after the cancellation of that plan, the goal of the smaller Pioneer 5 remained to be put into a solar orbit with its perihelion at Venus' orbit -- and after sitting on the pad through delay after delay during the last half of 1959, it finally got off the ground in March 1960 and became the only genuine success of the early Pioneers (although its perihelion ended up considerably outside Venus' orbit, and its power supply failed at a range of 22.5 million miles instead of the 50 million hoped for). The plan to launch a single Atlas-Able orbiter to the Moon remained; and after its planned October launch was scrubbed when the booster blew up during a September static test, NASA grabbed the Atlas planned for the cancelled second Mercury "Big Joe" test and launched it in late November -- only to end up with the infamous "turkey shoot" in which the shroud came off due to inadequate venting of internal air pressure, and the air blast then tore off the probe and third stage and crippled the second stage. No doubt this would have been its fate had it been launched to Venus in June.

Since this meant that there was still one spare Pioneer orbiter, Eisenhower gave permission to try to launch it to the Moon in late 1960 -- and to build a third copy for one last attempt if the second one failed. Unfortunately, both the second AND third tries also failed ignominously (due to failures of the second stage, which by then was usually working pretty reliably on Thor-Able). Both these versions had slightly changed science instruments -- the IR farside spin-scanner was removed and replaced by the first plasma probe on any NASA spacecraft, for instance. All the instruments on those two 1960 lunar orbiters were fields and particles; pretty much the only information they could have gotten on the Moon itself was to look for a magnetic field, but then that was also the case for Explorer 35. And so ended one of the stranger (and sadder) forgotten stories of the early Space Age.