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Mars calendar, mission sols in a standard calendar
Phil Stooke
post Apr 30 2012, 02:38 PM
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This file is something I put together to relate sols for all Mars lander missions to the standard Mars calendar devised by Clancy et al. and now widely used with orbital data. I'm posting it in case it might be useful to others.

It's an Excel file, so it can easily be extended if necessary. Each mission is given three columns, one for mission sols on the surface (some start with sol 0, some with sol 1, according to mission usage), one for the Mars year and one for the sol of that year.

Please note that there may be discrepancies of one sol here and there because I am simplifying things quite a lot here. For instance, MER-A and MER-B are half a planet apart, so their sols are half a sol out of phase, but I'm ignoring that in relating them to the planet-wide sol of the Clancy system. Details of the Mars calendar can be found on Emily's website at:

http://www.planetary.org/explore/space-top...s-calendar.html

(I have made independent lists of Mars historical dates in my forthcoming Mars atlas). And conversions to Earth dates can be made via this VERY useful website:

http://www-mars.lmd.jussieu.fr/mars/time/martian_time.html

Phil

Attached File  mars_calendars.xls ( 323.5K ) Number of downloads: 213


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tanjent
post Apr 30 2012, 10:46 PM
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Trying to figure what happened in 1955 to mark the base year. Must be so obvious that it doesn't get routine mention detectable in my brief attempt to Google it. Forgive me for asking rather than conducting a more thorough search. (In my personal planetary time zone, it's about time to head to the office.) My best WAG is that it's the publication year of something by Clarke, Bradbury or Heinlein.
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djellison
post Apr 30 2012, 11:00 PM
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It seems that most quote :

QUOTE
An intercomparison of ground-based millimeter, MGS
TES, and Viking atmospheric temperature
measurements' Seasonal and interannual variability of
temperatures and dust loading in the global Mars atmosphere
R. T. Clancy, B. J. Sandor, 2 M. J. Wolff, P. R. Christensen,
J. C. Pearl, 4 B. J. Conrath, 5 and R. J. Wilson


As the source for the 1955 date. In that paper, they simply say:

QUOTE
For the purpose of this comparison, we
use the solar longitude range 0-360 to define a Mars
year and adopt April 11, 1955 (L$=0 ) as the beginning
of year 1. In this arbitrary convention, the Mariner 9,
Viking, Phobos, and Pathfinder missions occurred in
years 9-10, 12-15, 19-20, and 23, respectivel
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Phil Stooke
post May 1 2012, 12:16 AM
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The 1955 start date is designed to be just before the global dust storm of 1956, the first one to be investigated in detail. This calendar system was originally set up for atmospheric studies.

Phil


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mwolff
post May 3 2012, 02:43 PM
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QUOTE (Phil Stooke @ Apr 30 2012, 07:16 PM) *
The 1955 start date is designed to be just before the global dust storm of 1956, the first one to be investigated in detail. This calendar system was originally set up for atmospheric studies.

Phil



As the citations indicates, it was an essentially arbitrary choice. However, the fact that 1956 was an International Geophysics Year and that it had the best Mars "opposition" for the previous 15 years led to a lot of attention for Mars (including the beautiful imagery in Slipher's book of 1962). So, it was a confluence of things including the dust storm...including the wish to avoid the need to large numbers at present. It was not Clancy's birthday (and he has expressed happiness of not having chosen that year...since he wasn't really thinking about how that would look).

There has been some debate (among a very small number of people) about what would have been a better choice. However, it boils down to the fact that this system is in use and it seems that many of the people who propose different zero-points don't actually use the system.
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Phil Stooke
post May 3 2012, 02:56 PM
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In fact I have never seen any other system used beyond the person or group who devised it. This particular calendar is in widespread use in the literature and in PDS documentation.

Phil



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