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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Guest_BruceMoomaw_* |
Apr 30 2005, 01:35 PM
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Guests |
Yep, that's all correct. (Don't ask me how I remember exactly how many command words in memory Mariner Mars '71 had, when I have no idea how many any later spacecraft had...)
While the '69 Mariners were indeed a complete quantum leap upwards from the earlier Agena-launched Mariners in many ways, though, I think the most dramatic was the incredible leap in their communications rate from 8 bps for the earlier Mariners to fully 16,200 bits for the '69 Mariners. I couldn't believe that figure when I first read it in 1968 and thought it was a misprint -- especially since the earlier design for the "Mariner B" line of spacecraft on which Mariner 69 was patterened only had a bit rate of (I think) 256 bps. However, there had been very dramatic improvements in communcations technology since Mariner B was designed in 1962, and NASA decided to take full advantage of them. Mariner 7's recovery from near-disaster was indeed very lucky -- although not as lucky as the incredible Perils of Pauline experiences of Mariner 10, when they practically had pieces fall off the spacecraft all the way to Mercury. (I suspect it was that experience that soured NASA on cost-control programs for some time.) |
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Oct 29 2005, 02:22 AM
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Member Group: Members Posts: 447 Joined: 1-July 05 From: New York City Member No.: 424 |
In Bruce Murray's book "Journey into Space: The First Three Decades of Space Exploration" (1989), Murray gives an account of of a coup he pulled off for one of the early planetary spacecraft, which might be relevant to the quantum leap to which Bruce refers.
In the process of designing a mission, Murray was frustrated by the bandwidth limitations of communications with the Deep Space Network. Despite what Murray described as a policy of DSN to reveal as little information as possible to other NASA centers, an unguarded remark in a paper by a DSN engineer gave Murray an inkling that DSN's actual communications abilities were substantially (orders of magnitude?) better than it was willing to admit. Murray made them 'fess up, and the mission's product return goals were substantially increased. *** My memory tells me that this anecdote related to a sixties mission and that the destination was Mercury, but one of these must be false, since Mariner 10 wasn't launched until 1973. I owned the book briefly when it came out, thanks to an enthusiastic review in the NYT, despite the fact that my interest in space exploration was in a decades-long lull that didn't pass until December 2003. I had expected an armchair tour of Pioneer, Voyager, etc., and was disappointed by Murray's focused recollections of small group interactions and institutional politics. I had to borrow another copy from the library to reread it last spring, when I found it much more interesting. The account of early Shuttle politics is grimly fascinating. Murray also singles out for criticism one or more eighties NASA administrators who couldn't be bothered to show up for important unmanned spacecraft rendezvous. The more recent administrators are doing much better. Tom Tamlyn QUOTE (BruceMoomaw @ Apr 30 2005, 09:35 AM) While the '69 Mariners were indeed a complete quantum leap upwards from the earlier Agena-launched Mariners in many ways, though, I think the most dramatic was the incredible leap in their communications rate from 8 bps for the earlier Mariners to fully 16,200 bits for the '69 Mariners. I couldn't believe that figure when I first read it in 1968 and thought it was a misprint -- especially since the earlier design for the "Mariner B" line of spacecraft on which Mariner 69 was patterened only had a bit rate of (I think) 256 bps. However, there had been very dramatic improvements in communcations technology since Mariner B was designed in 1962, and NASA decided to take full advantage of them.
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Nov 29 2005, 05:40 AM
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Senior Member Group: Members Posts: 2542 Joined: 13-September 05 Member No.: 497 |
QUOTE (Tom Tamlyn @ Oct 28 2005, 06:22 PM) In the process of designing a mission, Murray was frustrated by the bandwidth limitations of communications with the Deep Space Network. Despite what Murray described as a policy of DSN to reveal as little information as possible to other NASA centers, an unguarded remark in a paper by a DSN engineer gave Murray an inkling that DSN's actual communications abilities were substantially (orders of magnitude?) better than it was willing to admit. Murray made them 'fess up, and the mission's product return goals were substantially increased. Not quite. The mission was Mariner Venus-Mercury 1973 (aka Mariner 10) but the realization was that if the bit error rate was increased the bit rate could also be increased, and with imaging it didn't matter much if the bit error rate was higher, since isolated bad pixels could be removed with simple filtering techniques (such as median filters.) MVM73's bit rate was 117 Kbps at a BER of 5e-3 for this reason. See http://history.nasa.gov/SP-424/app-b.htm for more info. -------------------- Disclaimer: This post is based on public information only. Any opinions are my own.
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