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Targets for LRO
Guest_Zvezdichko_*
post Jul 17 2009, 09:45 AM
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Well, this will still allow us to see something
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djellison
post Jul 17 2009, 12:48 PM
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QUOTE (Paul Fjeld @ Jul 17 2009, 03:25 AM) *
But assuming 1.2 meter/pixel at the 120km altitude, the LM Descent Stage and its shadow should be defined by no less than 70 pixels.


The LEM is approx 4.5 metres across. At 1.2m/pixel - that's 3-4 pixels across, a total of perhaps 16 pixels of LEM.

Assuming a height of 4 meters ( which is generous) - and illumination at 10 degrees - the shadow will be another 17 or so pixels long.

Doug
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Paul Fjeld
post Jul 17 2009, 02:30 PM
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Your calculations are close. The LM structure is 4.22 m across, but footpad edge to footpad edge (still bright Kapton?) is 9.45 m. I would add the gear to show up as another pixel at least making the LM 25 pixels (5 ^2). The top of the LM Descent Stage structure is 3.18 m but the tops of the plume deflectors are at 4.23 m. So the shadow trig has it from 18 to 20 meters long. So 17 or slightly fewer pixels not squared but maybe a third of that is at least 75 pixels. So I revise my estimate upwards: the LM will be defined by at least 100 pixels.

Then there will be extra flotsam like the brightly lit backpacks and other things. We'll know soon!

EDIT: of course I'm neglecting slant range: this all assumes LRO was nearly right above the site when the pic was taken.
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djellison
post Jul 17 2009, 02:53 PM
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Oh - ok - you were counting ALL the pixels. Anyway - I started a new LRO thread for Apollo sites - we'll need it in about an hour or two hopefully smile.gif
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jmknapp
post Jul 17 2009, 03:01 PM
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QUOTE (Paul Fjeld @ Jul 17 2009, 10:30 AM) *
EDIT: of course I'm neglecting slant range: this all assumes LRO was nearly right above the site when the pic was taken.


Since the ground tracks on successive passes are about 30 km apart, and the vantage point is 120 km high, I suppose there needn't be much slant (15/120 = 7 degrees).


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glennwsmith
post Jul 18 2009, 08:31 AM
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John Moore, thanks for link to details on Arecibo radar mapping of the Moon's poles. So, there was no magic involved -- Arecibo had the same oblique view that we do, and as a result was only able to examine 25% of the craters' permanently shadowed areas -- and obviously not the deepest areas. Thus, as someone else mentioned, there is still hope that real "hit it wth a pickaxe" ice can be found on the moon -- lunar gold!
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John Moore
post Jul 18 2009, 10:45 AM
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Re: Arecibo + radar.

Glenn, you're welcome...had been reading up on it just a week earlier, so it was close to hand smile.gif

John
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Guest_Zvezdichko_*
post Jul 19 2009, 02:57 PM
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Uh... what happened to the other thread?
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Phil Stooke
post Jul 19 2009, 03:26 PM
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Yes, I was wondering that... but it's back now...

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... because the Solar System ain't gonna map itself.
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glennwsmith
post Jul 21 2009, 01:30 AM
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Given that the main goal of LCROSS is to search for water ice at the moon's south pole, I suppose this is an appropriate place for the following comment, namely, that the success of said search -- and I am not predicting here that it will be successful -- will pretty much end the Mars vs. Moon debate in respect to which of the two receives our next big push. But that becomes another topic for another time and place . . .
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Paul Fjeld
post Aug 5 2009, 11:55 AM
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QUOTE (jmknapp @ Jul 10 2009, 03:26 PM) *
I made an animation of the LRO passes over the Apollo 11 site, using the "mission baseline v8" data given at http://lroc.sese.asu.edu/downloads.html.

They updated the file to v10. It looks like it tracks pretty closely with the imaging data now.
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jmknapp
post Aug 5 2009, 12:13 PM
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QUOTE (Paul Fjeld @ Aug 5 2009, 06:55 AM) *
They updated the file to v10. It looks like it tracks pretty closely with the imaging data now.


I downloaded the v10 files and indeed it tracked well, differing from the position given by http://lroc.sese.asu.edu/whereislro/ by only a few minutes. BTW, the "Where is LRO" site now seems to be gone (check link). So the question becomes "Where is Where is LRO?"

I hear that up-to-date SPICE kernels are provided to the various centers on a daily basis but those aren't available to the public. That contrasts to, say, MRO, where updated files are continually posted to the NAIF public website, including both planned and as-flown instrument pointing files (so-called CK kernels). Cassini also does this. My understanding is that the older programs (particularly Cassini, being an old-school big budget project) were more committed to this. In Cassini's case, they even provide "science plan" kernels containing text information about the type and purpose of observations, correlated with instrument command sequences.

Eventually the pointing and trajectory files will be posted to the PDS, but only after 8 months or something like that. So near real time for LRO looks to be a no go, as far as the public is concerned.


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Paul Fjeld
post Aug 5 2009, 03:19 PM
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I have no idea how much effort it takes to keep going something like "Where is LRO." I would think it would be trivial: just point some telemetry or tracking data at an automatic web thingy and off you go.

I wish NASA would, as a matter of course, maintain an up to date data stream of a mission's state vector and attitude. They could have a standard web protocol and each mission's data folks would plug those 9 numbers in with a time stamp (every minute or second) and we could all do with it what we wanted. We would know where pics were taken from instantly and, where there are interesting mission events, simulate them if we have the skill or interest. Planetariums could fly along with some missions - landers would be especially fun to follow in "real" time.
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