Mariner Mars 1964, Mariners 3 and 4 to Mars: imaging plans? |
Mariner Mars 1964, Mariners 3 and 4 to Mars: imaging plans? |
Apr 28 2005, 05:05 PM
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Solar System Cartographer Group: Members Posts: 10226 Joined: 5-April 05 From: Canada Member No.: 227 |
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 -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PDF: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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Guest_BruceMoomaw_* |
Nov 29 2005, 05:56 AM
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Guests |
Fawning won't be necessary. It was indeed the originally planned destination of one of the 1959 Atlas-Able probes. It and the probe that later became Pioneer 5, after being launched in 1960, were to be launched in the direction of Venus in the first few days of June 1959 -- but Pioneer 5 (lauched by a Thor-Able, later to be renamed Thor-Delta) had no midcourse correction system and so would certainly have missed Venus by a great distance, whereas the spin-stabilized Atlas-Able probe had two hydrazine engines pointing out its two poles. The rearward pointing one could be fired four times; the forward-pointing one only twice (at least in the lunar version), with one of those burns being for final orbit insertion -- but apparently they had some confidence that this awkward setup could put them close enough to have a shot at orbiting Venus.
This thing came astonishingly close to being launched -- the front-page headline for the NY Times on (I believe) May 1, 1959 shows the mission being cancelled only then, apparently because the planned science experiments couldn't be gotten ready in time. I've spent years trying to find out what those experiments were, but the only clue I've found is a single paragraph in a 1959 issue of "Astronautics" magazine quoting a Lousisiana Congressman on "Meet the Press" who very briefly described them in a way which implies that they were exactly the same as on the second Atlas-Able Pioneer, which was scheduled for a launch to the Moon later in 1959. That is, they were particles and fields experiments, plus an IR photometer that could build up a low-resolution spin-scan map -- of the Moon's farside, or (presumably) Venus' cloud tops. (I'd assume that such a craft could have carried a UV photometer like Mariner 5's, to measure the planet's atomic H and O and thus provide an indirect estimate of its water vapor; but this wasn't mentioned. I also presume that it could, in any case, have carrried out radio occultations of Venus' atmosphere.) At any rate, after that cancellation, Pioneer 5 was rescheduled for a launch in late 1959 into a solar orbit with its perihelion at Venus' orbit -- and after months of technical delays it ws finally launched in March 1960, although the booster underperformed somewhat and so it fell well short of reaching Venus' orbit. They had hoped to communicate with it at distances of up to 50 million miles, but a slow battery leak finally silenced it 22.5 million miles out -- which still utterly shattered Pioneer 4's radio-range record of 407,000 miles. The Atlas-Able probe was rescheduled for that single launch to the Moon on Oct. 3 (a day before the Russians launched Luna 3), but its Atlas booster blew itself to kingdom come during a static test on Sept. 24, so they drafted the Atlas that had been scheduled for the second unmanned Mercury "Big Joe" test (which had been cancelled because the first was successful) and attached the Able upper stages and the probe to that instead. It took off on Nov. 26 and immediately failed ignominiously because its payload shroud hadn't been adequately vented and came off due to internal air pressure about 45 seconds after launch; the air blast quickly tore off the probe and the third stage, and damaged the second state enough to knock out its radio (apparently it then ignited without separating from the Atlas). This, of course, would have happened had it been launched to Venus. Since the cancellation of the Venus launch meant that they still had a second such probe built, the White House ordered a third probe to be built, one launch attempt to be made in 1960, and the third probe launched only if that first 1960 effort failed. Alas, they too both failed. (Neither carried that IR scanner; instead, they were the very first US spacecraft to carry plasma analyzers.) Clearly NASA's very early ambitions exceeded its grasp; the agency must have initiated this plan almost as soon as it was created at the start of 1959. It's very hard to find data on the Venus plan for this thing, but I first heard about it at age 11 from the space column of a 1959 back issue of "Sky & Telescope". You can find sprinkled references to it in other places, such as Aviation Week -- and notably that NY Times front-page headline article -- but about a decade ago, when I corresponded with one of the experimenters for the Atlas-Able probes' radiation experiments to try and get more information on it (he'd written a late 1980s nostalgic retrospective in a major science journal), I was thunderstruck to learn that HE had never heard of the Venus part of the plan! |
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