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: 10231 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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Nov 29 2005, 08:33 AM
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Senior Member Group: Members Posts: 1870 Joined: 20-February 05 Member No.: 174 |
Bruce Moomaw: ".... But they did come fairly close to adding an Earth-occultation photometer that could have told us what the cloud-top altitude was, which makes me wonder whether it might have clued us in to the clouds being sulfuric acid -- which instead wasn't discovered until 1973....."
I doubt it would have helped much. We actually "knew" what the cloud top altitude was from the visible/(and IR?) spectra of CO2, assuming the atmosphere was CO2 dominated, and not mostly nitrogen. And UV data indicated little Rayleigh scattering gas above the cloudtops, so there wasn't a huge over-abundance of Nitrogen. What we didn't know was the "altitude" o fhte suface below the cloud tops!.... where the bottom was. The expectation was that we'd eventually learn the cloud composition from infrared spectra, but that was "underinformative" and we weren't experienced enough to find a match to the so-so at best quality data we had. Somehow, people never included sulfuric acid in lists of candidates matched against cloud data so there never was a good match. A review article from the early 70's showed a distinct sense of frustration at the lack of progress and lack of signs of how to make progress in solving the problem. It took polarimetery data from earthbased observations to suddenly break the logjam. It showed with astonishing precision that the cloud particles were non-absorbing spherical droplets, about 2 micrometers in size with a narrow size distribution, and last but overwhelmingly most importantly ... a refractive index of 1.44 +- 0.01 (If I remember right). This totally blew away any candidates and yielded 90% sulfuric acid droplets as the only even close match.. and it wasn't close.. suddenly everything fit and made sense. |
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