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Posted by: elakdawalla Dec 23 2009, 03:53 AM

Hi folks, as I've been working on this advent calendar thing I thought it'd be fun to dig into the Viking archive on Deimos and make my own color composite (since Viking is, as far as I know, the only mission that's gotten views on anything other than the Mars-facing hemisphere). The data is quite a bit more gnarly than I anticipated. Thanks to Peter Masek's VikingOrbiterView software though I have put together a montage of all the halfway decent Viking Orbiter images of Deimos, and I thought you guys would enjoy. Attached also is a color composite from a set taken at random (made by making an R-G-V combo, mixing a bit of the green into the V because the V is a little underexposed, and then converting to HSB and swapping in one of the much nicer clear images for the brightness channel). Anyone else want to have a go at making a pretty color combo? Anyone have any helpful comments on the color? The images in the montage are not processed at all except for removing salt-and-pepper noise and (in a few cases) doing some destriping to correct missing lines, so there'd be nothing wrong with grabbing individual images straight from the montage rather than hunting down original files. I've posted the http://planetary.s3.amazonaws.com/misc/viking_deimos_all_despeckled_destriped.png.

The view in the attached color composite is primarily of the leading and southern hemispheres. Deimos has this weird squashed south pole -- I guess it's one big impact crater, but it's a crater with a diameter similar to that of Deimos itself.

Posted by: volcanopele Dec 23 2009, 04:55 AM

Of course, I can't help but playing with my paper Deimos model to get it to match the orientations seen in that montage

This, I think, is F507A01:

Posted by: tedstryk Dec 23 2009, 04:55 AM

Why must you do this to me right now I am supposed to be addressing birth announcements...

By the way, Phil Stooke has a cool resource for this
http://www.ssc.uwo.ca/geography/spacemap/deindx1a.htm
http://www.ssc.uwo.ca/geography/spacemap/dem9pics.jpg

Posted by: elakdawalla Dec 23 2009, 05:11 AM

How do you think I figured out how to orient the image I showed?

Ted: As gungy as I think these data are, I figured it was too easy for you!

Posted by: ElkGroveDan Dec 23 2009, 06:42 AM

If anyone can do it, Ted can

Posted by: scalbers Dec 23 2009, 09:07 PM

This is great, Deimos is more irregular than I had realized.

Posted by: JohnVV Dec 26 2009, 04:48 AM

you might be interested in my cmod 3d celestia model ( or a 3ds )
http://www.youtube.com/watch?v=g7A4RaaOzho

Posted by: scalbers Dec 26 2009, 03:31 PM

John - Looks very nicely imposing to see Deimos up close like that. I wonder if there is a Viking ephemeris for Celestia that can be used to reproduce some of the image situations for comparison? I suppose getting Deimos' rotation correctly into an ephemeris could be tricky.

Posted by: JohnVV Dec 27 2009, 05:05 AM

no , but there is a spice set for deimos and phobos .I was using "mar080.bsp" in isis to work with the images .
so the kernel can be used in celestia .I just have not done it yet .It is on the list of things to do

Posted by: PhilCo126 Dec 27 2009, 01:24 PM

Phobos:
First imaged by Mariner 7

Deimos:
First imaged by Mariner 9

The 1971 Mariner 9 pictures were the basis for the first two-dimensional US Geological Survey maps of the Martian moons.
In 1975, a rubber mould for globes of Phobos was constructed by scientific modeller Ralph J. Turner at a scale of 1:60000
After the 1977 Viking orbiter 1 and the 1989 Phobos 2 spacecraft encounters, new mapping accuracies became available and Ralph Turner created another Phobos globe and a Deimos globe on scale 1:100000
Additional Phobos and Deimos globes at scale 1:50000 were made by Astrophysics departments of the Martin Luther University (Wittenberg - Germany) and the Max Planck Institute (Munchen - Germany)

What on earth would make you post a list of random facts only tangentially related to the thread?

Posted by: PhilCo126 Dec 28 2009, 05:29 PM

Well, the post started with a wrong fact (Viking first to image a Moon of Mars) and the other info adds to the topic
Or should/may I start a new topic on Martian Moon globes so I can share photos?

Posted by: ugordan Dec 28 2009, 06:19 PM

That is not what the opening post says.

Posted by: PhilCo126 Dec 28 2009, 07:32 PM

Indeed, I've read that too fast... ( Mars-facing side of Deimos )
Here's some nice " shaded relief " by Phil Stooke: http://www.gis.unbc.ca/courses/geog205/lectures/current_trends/deimos.jpg

Posted by: JohnVV Dec 28 2009, 11:08 PM

back to the orig post

go with your gut . i know that is not scientific but even the nasa color of Deimos and Phobos are only close guesses
i used these as a guide for my maps
http://hirise.lpl.arizona.edu/deimos.php
http://hirise.lpl.arizona.edu/phobos.php
http://photojournal.jpl.nasa.gov/target/Deimos
http://photojournal.jpl.nasa.gov/target/Phobos
and old sites
http://www.nineplanets.org/phobos.html
http://www.nineplanets.org/deimos.html
the two moons will have some red in them from dust from mars getting ejected by impacts

so if it is consistent with the above examples and looks nice ...

Posted by: HughFromAlice Jan 1 2010, 10:56 PM

Your YouTube vid of Deimos rotating was v good ***** ! Liked your photo Emily and may take up the challenge (although back to work in a day or so).

IMO close guesses are about as near to 'ground truth' as we are likely to get. Even with a calibration target in situ to refer back to, there are so many intervening variables that perhaps even a Jim Bell or David Malin would scratch their heads just a little bit.

The reproduction of great paintings in the most expensive art books is a good case in point. When I see one of them (by itself) I think (assume!) that it is like the original! But, open a couple of books and put two different reproductions side by side and the naked eye can see the differences between them.

Electronic technology is even more variable. A couple of examples from many
- Even with improvements in the html environment converting a graphic produced in RGB or CMYK to hexadecimal (web 'safe' colours) is not seamless
- The angle that you look at a PC Monitor effects what you see... the same pic looked at just a few degrees away from level line of site appears to lose saturation and contrast.

The big q to me is what do you want to produce the image for. A scientific paper? A popular book like Postcards From Mars? A web pic on UMSF? Space Art?

The challenge that I personally enjoy is that working on images like these requires a thoughtful balance between science and interpretation(experience + art) depending on what you are producing the image for and the strengths/weaknesses of the tools that you have at your disposal. On UMSF, to pick two good contributors among many, there is a range from a James Canvin (more scientific) to a Stu (more interpretive)... I get inspiration from both of these approaches depending on what I am looking for.

Posted by: Phil Stooke Jan 11 2010, 07:34 PM

This was an attempt I made about 10 years ago to fix up the 413b90 sequence of Viking images of Deimos:

Phil

Posted by: jasedm Apr 27 2023, 07:06 PM

Some crisp images of Deimos from the UAE 'Hope' spacecraft including one with Mars as a stunning backdrop:

https://www.universetoday.com/161077/new-high-resolution-photos-of-deimos-from-the-hope-mission/