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Mars Clock
James Tauber
post Aug 15 2012, 12:17 AM
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I recently built this:

http://jtauber.github.com/mars-clock/

It's a single web page with calculations being done live in Javascript.

It started off just as a way to calculate the LMST and LTST for Curiosity but it has a range of calculations for Mars overall from Allison and McEwen's 2000 paper.

Recently I've started adding explanations of each of the calculations including the formulas used.

It's been a huge learning experience for me and I'd appreciate any feedback, both in terms of experts correcting what I've done incorrectly and amateurs such as my self saying what they'd like elaboration on.


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Astro0
post Aug 15 2012, 01:16 AM
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James, nice first post. Great contribution. This is what we like to see on UMSF.

Secondly, a question. Where does it get it's time reference from?
Is it a reference from an online time code source or is it getting its reference from the system clock on the local computer?

Also, just in terms of layout. Any chance of putting the clocks across the page with the mouse-over explanations underneath perhaps. It would save scrolling.
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maschnitz
post Aug 15 2012, 03:40 AM
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That's the great part of his work - you can check yourself how he did it:
QUOTE
var d = new Date();

(line 385) He's getting it from the browser, which in turn asks the system.

There's some offset between the various seconds ticking over. By reading the code, I take it that's a base amount you added on purpose to align the clock to the actual timekeeping millisecond, right?

The code's nice. The only two suggestions I'd make are, 1) setInterval at 10ms might not work so well on older browsers, especially IE8. Perhaps change the interval time based on the browser? 2) maybe for speed on that milliseconds display, update the texts during update via getElementById() rather than jQuery (but I doubt that's much of an improvement - jQuery's pretty fast, especially on post 2010 browsers)

Nice work!
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elakdawalla
post Aug 15 2012, 04:47 AM
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This is fantastic. Useful and also quite pretty to look at. Please add Opportunity!

Usually when I'm looking for Mars time I'm looking to figure out Ls for a past date or the Earth date corresponding to a sol date or some such. I can do this using Mars24, but it's kludgy. I would love to have an easier way to do that (though I am not sure what I'd recommend as far as a user interface for that goes.)


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Gsnorgathon
post Aug 15 2012, 06:29 AM
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I'm a big fan of separators to make it easier to see thousands, millions, &c.
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James Tauber
post Aug 15 2012, 09:07 AM
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QUOTE (elakdawalla @ Aug 14 2012, 11:47 PM) *
This is fantastic. Useful and also quite pretty to look at. Please add Opportunity!


I'll investigate adding Opportunity now :-)

QUOTE (elakdawalla @ Aug 14 2012, 11:47 PM) *
Usually when I'm looking for Mars time I'm looking to figure out Ls for a past date or the Earth date corresponding to a sol date or some such. I can do this using Mars24, but it's kludgy. I would love to have an easier way to do that (though I am not sure what I'd recommend as far as a user interface for that goes.)


I could try add separate pages for that. Let me add Opportunity first then I'll see about that.
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James Tauber
post Aug 15 2012, 09:31 AM
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QUOTE (Gsnorgathon @ Aug 15 2012, 01:29 AM) *
I'm a big fan of separators to make it easier to see thousands, millions, &c.


Done!
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James Tauber
post Aug 15 2012, 10:02 AM
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QUOTE (James Tauber @ Aug 15 2012, 04:07 AM) *
I'll investigate adding Opportunity now :-)


So far I haven't been able to confirm how mission time is calculated for MER-B Opportunity.

http://www.giss.nasa.gov/tools/mars24/help/notes.html says

QUOTE
offset modification of an evenly advancing mean solar time


but also

QUOTE
at approximately the middle of each of the MER A and B nominal missions (i.e., on the 45th sol after landing), lander mission time should align with Local True Solar Time to within 30 seconds.


and, in either case, I don't know the longitude to use. The values I've tried (such as 354.5 E) don't give a mission time anything like what Mars24 gives.

Perhaps I should ask on the Rover-specific forum. (mod: deleted duplicate thread)
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James Tauber
post Aug 15 2012, 10:32 AM
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QUOTE (James Tauber @ Aug 15 2012, 05:02 AM) *
So far I haven't been able to confirm how mission time is calculated for MER-B Opportunity.


Nevermind, I've worked it out.

It's calculated as Coordinated Mars Time / AMT -01:01:06.

I guess I could translate that to a longitude but there's no need to for my purposes.
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James Tauber
post Aug 15 2012, 10:47 AM
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QUOTE (elakdawalla @ Aug 14 2012, 11:47 PM) *
Please add Opportunity!


And, done!
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fredk
post Aug 15 2012, 03:23 PM
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This is looking good, James. Your Oppy time agrees well with Lemmon's Oppy clock, which shows LMST. What is HLST?

Your Oppy clock differs from the MER filenames clock, but then that one shows LTST.
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elakdawalla
post Aug 15 2012, 05:04 PM
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Awesome work! And well done with the explanations. I'll link to it in my next posts about Curiosity and Opportunity. I suggest you add a link to your clock in your signature on this forum -- saves people hunting for it and people asking "where is that clock again?"


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James Tauber
post Aug 15 2012, 07:06 PM
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QUOTE (fredk @ Aug 15 2012, 11:23 AM) *
This is looking good, James. Your Oppy time agrees well with Lemmon's Oppy clock, which shows LMST. What is HLST?


HLST = Hybrid Local Solar Time (according to http://en.wikipedia.org/wiki/Timekeeping_on_Mars)

I first saw the term used on http://www.lpl.arizona.edu/~lemmon/mars-tau-b.html (presumably the same Lemmon smile.gif )

QUOTE (fredk @ Aug 15 2012, 11:23 AM) *
Your Oppy clock differs from the MER filenames clock, but then that one shows LTST.


If HLST is in fact LMST (which Lemmon's Oppy clock suggests it is) then I should be able to add LTST easily (as I just need to add the equation of time)

Thanks!
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James Tauber
post Aug 17 2012, 02:15 AM
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I've added LTST for Opportunity but it disagrees with http://www.greuti.ch/oppy/html/filenames_ltst.htm

I just added the equation of time to the LMST but not sure what the other site is doing differently.
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helvick
post Aug 17 2012, 05:51 AM
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LTST caused Tman issues when he built that if I recall correctly. I know there was a +-10 minute error problem at one stage but I can't recall how he corrected it. I remember that he used an old perl script of mine to look at an alternative way to calculate it but my code was based on the same sources as yours and I haven't looked at it in years so I can't throw any light on the issue right now.

You might find something in the original discussion here and it could be worth sending a PM to Tman. He hasn't logged in since late last year but a PM might alert him by e-mail and elicit a response.
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