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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Apr 30 2005, 08:36 AM
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Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
Bruce.. that matches what I recall without digging into the archives. I expect the design was intended to be able to find the planet, even if command capability had been lost and the flyby geometry was poorly known.
I'm still at a loss to understand why missions like Galileo and Cassini don't have "planet sensors" to help with fine targeting during close encounters. Cassini's lost full disk mosaics of moons just cause the targeting was say 50 or 100 km off and a big chunk of limb was clipped. Mariner 69 was the "bridge" to everything later. Mariner 62 and 64 had "central computers and sequencers", but they weren't reprogrammable in flight. Mariner 69 had 128 or 256 command-words of storage. (Mariner 9 in 1971 had (I think) 512.) With that added command capability, they were able to reprogram Mariner 7 to take a full tape recorder load of some 33 pictures instead of about 24 that Mariner 6 did, DESPITE having a Loss-of-Signal event and major spacecraft emergency only 5 days before, while Mariner 6 was doing it's close flyby. (They added more frames to the pass over the south polar cap and then let the tape run till it was full as it crossed the terminator over Hellas, trusting that real-time telemetry would get the nightside and night-limb data, as it had worked on Mariner 6.) Mariner 7's battery had overcharged, shorted, and *RUPTURED*, venting into the spacecraft, sending it into a roll, and giving a small propulsive nudge to the spacecraft from the vapors venting from the main body of the spacecraft! |
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