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Crossing the Dunes at Murray Buttes, Sites 54-, Sols 1353-, May 28 2016-
Art Martin
post Jun 7 2016, 06:28 PM
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Could it simply be that the material used for the ribbing is naturally magnetic?
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PaulH51
post Jun 8 2016, 01:22 AM
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Curiosity Mission Update by Ken Herkenhoff, dated 06 Jun 2016. Sols 1364-1365: Analyzing drill sample:
QUOTE
The Oudam drill campaign continues to go well, with sample acquired and ready for analysis. Planning is now restricted, so we are planning 2 sols today. On Sol 1364, ChemCam will acquire passive spectra of the drill tailings and a LIBS raster of the wall of the drill hole. Later that afternoon, the unsieved portion of the drill sample will be dumped on the ground and imaged by MAHLI from 25 cm to support future planning. After dark, MAHLI will take pictures of the inside of the drill hole, the tailings, and the CheMin inlet using its LEDs for illumination. The APXS will then be placed on the drill tailings for an overnight integration.
Early on Sol 1365, the Right Mastcam will extend the mosaic of Hartmann's Valley, adding 22 images. That afternoon, the APXS will be retracted and vibrated to clean it, then the arm will be moved out of the way for ChemCam and Mastcam observations of the drill tailings. Navcam will search for clouds both near the horizon and at zenith. Finally, CheMin will analyze the drill sample overnight.



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James Sorenson
post Jun 8 2016, 05:31 AM
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I like the "UV darkening of the adhesive" theory. The trouble that I'm having though with it possibly being adhesive is it appears to take an exact imprint of the pattern like the pattern was intricately cutout then bonded which would support what we are seeing but that seems a little unlikely. I would have thought the pattern would be printed on some sort of backing surface with then a uniform adhesive on the back, which is not what we are seeing if that was the case. Need more information on these particular fidicual targets, how they were made and applied, and why they were removed. Though the latter isn't as important to know.
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PaulH51
post Jun 8 2016, 11:31 AM
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QUOTE (James Sorenson @ Jun 8 2016, 01:31 PM) *
I would have thought the pattern would be printed on some sort of backing surface with then a uniform adhesive on the back, which is not what we are seeing if that was the case.

I really enjoy a good detective story smile.gif So I throw a possible clue onto the table (just for fun)...

I looked at the Photo-Journal page for PIA14131 which make reference to a 'space simulation chamber at JPL'

Google pointed me to the actual chamber used LINK which even has a photo of Curi in the chamber before the doors were closed.

The chamber contains a large 'collimating mirror' on the seiling that collects light from 37 xenon arc lamps installed in a 'solar basement,' and focuses the light onto a test subject. Each of the lamps are 20 to 25-kilowatts depending on which reference I found... the other link to the test chamber (Chamber 25 Space Simulator, Building 150) LINK

So, returning to Jame's comment about one piece labels with a uniform adhesive / UV darkening etc.

Xenon arc lamps produce a lot of light and a lot of UV, maybe enough to alter the backing adhesive of the temporary fiducial targets on the port covers. But why the different effects leaving our matching pattern behind? Possibly the intense UV from the xenon lamps passed through the black and white fiducial marks differently, one section being masked? Maybe this resulted in some change in sections of the uniform adhesive where some was altered or baked onto the surface?

Just another 2 cents towards this discussion smile.gif


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mcaplinger
post Jun 8 2016, 03:54 PM
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QUOTE (James Sorenson @ Jun 7 2016, 09:31 PM) *
I would have thought the pattern would be printed on some sort of backing surface with then a uniform adhesive on the back...

If you look at the original M34 raw images taken in the system thermal test (sorry, can't share), you can see that the background color is identical to the cover's, so there is no backing surface as far as I can tell at the resolution of the image. It looks like a cut decal, very conformal to the cover.

I don't know more about the story of this target, but I have some inquiries in.

[EDIT]
Ah, the full story. The covers were originally black-anodized but were found to be flaking ( http://llis.nasa.gov/lesson/8403 .) Seems like the original white target got stripped off when the covers were reanodized but there was some residual etching and that's what you're seeing.


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HSchirmer
post Jun 8 2016, 04:52 PM
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QUOTE (mcaplinger @ Jun 8 2016, 03:54 PM) *
If you look at the original M34 raw images taken in the system thermal test (sorry, can't share), you can see that the background color is identical to the cover's, so there is no backing surface as far as I can tell at the resolution of the image. It looks like a cut decal, very conformal to the cover.

I don't know more about the story of this target, but I have some inquiries in.

[EDIT]
Ah, the full story. The covers were originally black-anodized but were found to be flaking ( http://llis.nasa.gov/lesson/8403 .)


Hey, two birds with one stone- the crosshair pattern and mudcrack flaking.

Seems the rover's aluminum was developing a mini-mudcrack pattern as the anodized layer flaked off...


SEM images of the flaking surface showed a micro-cracking or crazing
of the surface with much of the anodize removed.
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Steve5304
post Jun 8 2016, 07:02 PM
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So this pretty much tells us mars atmosphere eats and corrodes stuff over a period of time. Much more than earth... That explains the wasteland of hollow rocks.
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fredk
post Jun 8 2016, 07:07 PM
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How does it tell us that? The anodized coating flaking was during testing on earth, if that's what you meant.

The pattern visible in mastcam now is due to residual etching according to mcaplinger. Perhaps it was especially noticable due to the large phase angle.
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HSchirmer
post Jun 8 2016, 07:28 PM
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QUOTE (Steve5304 @ Jun 8 2016, 07:02 PM) *
So this pretty much tells us mars atmosphere eats and corrodes stuff over a period of time. Much more than earth... That explains the wasteland of hollow rocks.


Sorry, I should have been clearer - Curiosity has tan lines.
Instead of spring breakers writing-on-somebody-with-sun-tan-lotion, it's engineers, sticker residue and aluminum that was re-anodized on earth.

Same end result, you can see the pattern where something protected the surface.

The part that seems poetic is that the covers had to be re-anodized because the anodizing flaked off, creating a mud crack pattern, likely due to temperature variation.
That same temperature crack pattern seems to appear on the exposed rocks around curiosity.
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mcaplinger
post Jun 8 2016, 08:32 PM
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QUOTE (HSchirmer @ Jun 8 2016, 11:28 AM) *
...sticker residue and aluminum that was re-anodized on earth. Same end result, you can see the pattern where something protected the surface.

To be clear, I don't think there was ever adhesive of any kind. I think the original white pattern was some kind of paint/marking ink (probably epoxy-based, that's what we use for labeling) that was stripped off when the cover was re-anodized.


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PaulH51
post Jun 8 2016, 08:49 PM
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QUOTE (mcaplinger @ Jun 9 2016, 04:32 AM) *
... I think the original white pattern was some kind of paint/marking ink (probably epoxy-based, that's what we use for labeling) that was stripped off when the cover was re-anodized.

Thanks for solving this puzzle smile.gif

I have one remaining question. The reworked cover contains a single white line in place of the fiducial marker on the anodised cover, does that line perform a similar role to the earlier markers? Or does it have a different role?


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mcaplinger
post Jun 8 2016, 09:24 PM
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QUOTE (PaulH51 @ Jun 8 2016, 12:49 PM) *
The reworked cover contains a single white line in place of the fiducial marker on the anodised cover, does that line perform a similar role to the earlier markers?

I don't see what you're talking about. As far as I know all of these targets were used for arm checkout and don't have any ongoing operational role, but I could be mistaken.


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HSchirmer
post Jun 8 2016, 09:31 PM
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QUOTE (mcaplinger @ Jun 8 2016, 09:24 PM) *
I don't see what you're talking about. As far as I know all of these targets were used for arm checkout and don't have any ongoing operational role, but I could be mistaken.




Eh, pretty sure it is the a white line across the lower portion of the "ping-pong-paddle".

Hmm, seems like the "handle" is a bit darker than the "face"
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mcaplinger
post Jun 8 2016, 10:35 PM
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QUOTE (HSchirmer @ Jun 8 2016, 01:31 PM) *
Eh, pretty sure it is the a white line across the lower portion of the "ping-pong-paddle".

I think that's a step in the face of the cover, not a color difference, but I could be wrong.


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serpens
post Jun 8 2016, 11:10 PM
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Kudos to fredk for the insight on phase angle which explained why I couldn't find the artefact on earlier deck images taken on Mars and thanks to mcaplinger for taking the time and effort to research the events that caused the anomaly.
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