MEX VMC - Back on, and online! Options

[Juramike]

I finally downloaded Celestia (slaps head, why did I wait so long?) and poked around Mars on the date of the observation time to line up the features (thanks for the suggestion, Gordan!).

The location of the cloud feature in post 14, this thread was identified (highlands around Kepler Crater [-47S, 220W])
and the caption/location of the mosaic in this post was identified and corrected.

Color me embarrassed.

-Mike

[EDIT: Oh great. This post is right at the top of the page...terrific...]

[Juramike]

Interesting how both the "mystery cloud" picture and the putative dawn cloud (post 35) are both located around the highlands of Terra Cimmeria.

Is this a known cloud zone?

-Mike

[ormstont]

...it seems the images are in two sections: a ~1hr period near apocenter, and another ~1hr period near pericenter....I'm assuming operations (downlink etc.) and other instruments prevent this from being done

Yep, you're right there - it's mainly instrument operations that constrain us to those windows. Aspera, a Swedish experiment looking into space plasma and energetic atoms aims to be on permanently to get a good dataset. However, every 3-4 orbits (~once per day) we have to perform a reaction wheel offloading and orbit maintenance, which means firing the thrusters. When we do this Aspera shuts down for an hour because the thruster plumes would interfere with their measurements. This thruster activity is always placed right after apocentre for maximum activity and that gives us our ~1 hour VMC window. Sometimes though these are impacted as you say by ground station passes a that's why we get our average frequency of 2-3 obs per week.

The VMC obs just after pericentre are much rarer and happen when we perform a orbit change, here we have to fire the thrusters to achieve this but the point of highest efficiency is at pericentre. Therefore Aspera shuts down and we get a relatively low-altitude VMC observation (assuming Flight Dynamics don't choose that period to obtain tracking data from the burn).

one VMC image every ~5 minutes for one full orbit would make for one amazing animation.

You're very very right here too (you could come work for us!), we'd all love to do a full orbit animation! As this would require agreement from all the other instruments though it will require quite some negotiation. I'm constantly on the look-out for chances though, but don't want to impact our prime science mission. The other slight problem is that the VMC packet store (like a directory on a computer) is limited to 60 images, so we'd have to ask nicely for another instrument to lend us their packet store

Color me embarrassed.

Lol....we all get embarrassed - how do you think we felt when we got our first VMC images and they looked like this: http://www.esa.int/SPECIALS/VMC/SEM4SJEVL2F_1.html#subhead4 ?! At least it makes for a cute story in the history of VMC I'll ask Daniel to update the captions for your images on the website. Even if they're of a slightly different location they're still great work!

[Juramike]

It's baaaack!

Another cloud sequence at sunrise over Terra Cimmeria taken one month after the post 35 cloud movie. This shows a much more impressive series of clouds. These are located near Electris Crater [-45S, 150W] in Terra Cimmeria.



(click to animate GIF)

The brightish crater at center is Copernicus crater at [-50S, 170W]. There was another dimmer cloud visible near the terminator just to the ESE of Copernicus crater but it wasn't as photogenic (or on all the frames).


All these used the first image (the most exposed) in the sequence of 4 exposures. These are beautifully spaced in 10 minutes steps for a neat time-lapse sequence of 1 h.

Terra Cimmeria seems to be a breeding ground for these clouds (3 for 3!). Might be nice for the next scheduled observation run that views Terra Cimmeria near the terminator to use the longer exposure times, and space the images at shorter time periods (3 to 5 min.). Then you can get a neat smooth movie, or do image stacking to pull up the contrast on a particularly nice set.

-Mike

[ormstont]

Interesting that we might have a cloud factory on our hands! I'll ask around and see if anyone here has any ideas why there should be clouds generated around this region. The instrument team did indicate to me though that we're going into a "cloud rich" season at the moment, so maybe it's just coincidental that most of our terminator shots recently have been around this region?

Also...I promised to update you on the exposure settings used. I'm still trying to work out a way to pass exposure information on every image through our automated processing chain. However, all recent images have used the 4-step exposure settings, with looping values of 0.4 ms, 6.8 ms, 14 ms and 22.8 ms.

For changing the exposure settings to better catch clouds - this is very possible, I'll try and have a look at what we can do and when we can do it - maybe come back to you and ask you to define your very own VMC observation

[ormstont]

Just a quick plug - got some more lovely shots from last week of the volcanoes...just gone up on the VMC website

[Juramike]

The thing that's been puzzling me is the appearance of the middle "rolling" cloud in the the sequence above. From the orientation of the image (S is roughly at top), it appears that the cloud stuff is moving/growing from S to N.

I would have thought that if there is a global redistribution caused by the CO2 freezeout at the cold high South Pole during the S hemisphere winter, then the overall circulation pattern (especially near the S pole) should go from N to S. This is in direct contrast to the image sequence.

This could be a parallax effect due to changing viewing angle, making the clouds way the heck up there. Or the "rolling" impression could be due to the cloud actually growing N towards the daylight due to the sun starting to warm and mix the upper layers of the atmosphere. (Kinda like the morning clouds you see here on Earth, just on a bigger scale).

I'm going to see if I can add the shorter exposure images (which I guess must be the 14 ms images) into the sequence to make a better resolution movie.

-Mike

[djellison]

I love this camera.

Attached thumbnail(s)

 

[Juramike]

Here is an attempted mosaic of the "relatively clear and kinda undistorted parts" of the MEX VMC images covering August 4-September 11, 2008.
(It's still a work in progress - mosaic is too strong a word, I was overlaying these images on the USGS Mars Map - it's more analogous to what the psycho killer guy was doing in "The Silence of the Lambs")



Here is an EXCEL table I made that lists the image date, approximate time, and the most distinctive feature nearest the center of the image for those MEX VMC images. This will hopefully cut down on the frustration of trying to figure out the features on the image:  MEX_VMC_Features_list_20080918__August_4___September_11_2008_.xls ( 19.5K ) Number of downloads: 688


-Mike

[Juramike]

There are few guarantees in life...
but finding clouds in morning light near [-45S, 193W] on Mars in one of them.

More MEX VMC images from July 6, 2008 and July 12, 2008 (impressive display) of sunrise clouds:



Both images lightly processed, the July 6 image came from the jpeg from the MEX VMC website, and the July 12, image was downloaded in RAW form, debayered through Gordan's latest tool, then pushed to grayscale, then contrast curve modified, and exposure modified. (All images rotated to fit the July 31st and Aug 31st orientation.)

This shows the identification of nearby craters:



-Mike

(For those of y'all keeping score: this is 4 sets of clouds out of 4 MEX VMC observations at this location.)

[dvandorn]

I seem to recall that clouds have been observed over Cimmeria for a long time, even back in the days when it was Mare Cimmerium and observed only through feeble terrestrial telescopes.



-the other Doug

[Juramike]

My surprise isn't the clouds forming over high topography in high latitudes, it's of finding a cloud that seems so localized. That little guy is always there at sunrise.
(The Sept. 7, 2008 MEX VMC images have yet another really nice sequence of clouds in the same location (5/5!) that I'm currently working on.)

The USGS altimetry map of Mars (links to immediate 2.1 Mbyte PDF download) shows two local high areas next to and running south of Cruls and Bjerknes Craters, with the cloud seeming to form in the area between them. Assuming the upper atmosphere circulation is aligned with the winter high latitude eastward jet (Britannica ref here), it would seem that the Bjerknes ridge might be causing a downwind upper atmosphere rotor.

*I think*

-Mike

BTW, if anyone has any lit refs on observations of Cimmeria clouds - please let me know. (Along with the Conan literature - I didn't find any specific articles - but a lot of general observations)

These clouds are not obvious in the MRO MARCI movie for the week September 1-7, 2008 (available here) . But these are in the southern edge of the movie area (and maybe these clouds are only evident at sunrise?)

[Juramike]

Animated GIF showing the September 7, 2008 sunrise clouds of Terra Cimmeria:

(click to animate GIF)

This uses both the longest and second longest exposure images (I adjusted the exposure level so they would match up). Interesting to see the two clouds closest to the daylight portion fade out either due to dissipation or lack of sufficient contrast against the brightening background. Also cool how the sun starts lighting up clouds further back as dawn progresses. (Would be neat to see this from the surface, probably really pretty).

-Mike

[Please ignore the things shooting across the surface from lower right to upper left, those are camera artifacts I wasn't able to totally remove after contrast enhancement.]

[Juramike]

Montage showing the sunrise clouds near Bjerknes Crater for the 5 observations between July 7 and September 7, 2008.


(click to animate GIF)

Images are all centered on Copernicus Crater, I tried to correct for rotation and viewing angle as best I could. The image used was the last, longest exposure image on the observation day. No contrast enhancement or additional exposure correction was used.

-Mike

[ormstont]

Hi all, looks like some brilliant work is going on as usual - once again my congratulations on pulling so much from the VMC images! Just by way of a quick ops update, we've got another two or three nice observations which should be going online soon, some with some interesting linear(ish) surface brightness features you might be interested in checking out.

For the things that have been posted here - first off, Doug - the spinning volcanoes - would love to post that on the VMC website, if you could just add the information that's at the bottom of the "Help us with VMC" page and stick that on an e-mail to us that would be great on the site.

For the clouds work that you've been doing Mike - it's a really interesting study into our little "Cloud Factory" that we've found. I don't know how much longer we'll stay over this area - I guess the orbit evolution will move us away eventually. When you've got enough info though if you want to put your animations, images and plots together with text explaining all you've found and maybe referencing other texts, we could post an article on the VMC website about the VMC cloud factory at Terra Cimmeria!