MEX VMC - Back on, and online! Options

[ormstont]

Yep, that was certainly my thinking, I want to leave the zip of the raw files exactly as-is, all the processing I do there is literally stripping the data out of the downlink packets, removing packet headers and splitting them into individual images. For the "instant gratification" PNG images though this could be a really nice addition. I also might look into systematically boosting the colour levels or sharpening as described if it's possible.

Just as some background...what currently happens is my Java software does the stripping described above (into the raws) then I call from Java ugordan's vmc2rgb v2 convert them into PNGs and then the Java packages it all up and posts it on the blog. The aim is to keep it "hands off" so no operator needs to be present and the time from downlink to being online can be kept as short as possible. Therefore we would need to work out a way to either implement any enhancement in my Java code or in vmc2rgb or a similar external exe that could be called from the command line.

Any ideas or suggestions let me know!

[ElkGroveDan]

do we think a real flat-field observation would bring significant improvements on the already stunning improvements just shown by ugordan?

If it isn't a huge ordeal from your end to create one, (or maybe three) I'd say yes and I'm sure Gordan would agree.

[ugordan]

Also would be great if we could post a small article about how flat-fielding works and how you derived it for VMC (also an image of the flat field to see how messy the camera really is!). Thanks in advance!

The .raw file can be opened in Photoshop as a 640x480, interleaved 3-channel 16 bit image in IBM PC byte order. Here's a jpeg version:

It's actually the flatfield multiplied by 32768 (as pixel normalization factors are centered around 1.0) so as to fit into a 16 bit image and so I don't need to use 32 bit floating point images.


The way I created it was stacking a whole bunch (134) of recent images which weren't overexposed in Registax. This provided a good flatfield portion for the center and lower part of the detector because sharp limb contours infested outer parts of the stacked image:


I then applied a median filter to that image to remove most of the small scale details that affect VMCs noise the most. I then divided the two images and this resulted in my base flatfield - essentially only leaving the high frequency noise and manually taking care of the larger blemishes present. I used another older observation that had Mars fill most of the screen at low phase to produce another flat in a similar way and to mask out the circular arcs in the lower part of the image edges and in the upper portion. It's not a perfect result and rings are still plainly visble in the flatfield above, but I don't have a good way of getting rid of those. Making flatfields is not really my area of expertise.

The caveat of me using a median filter is that only the high frequency noise is flatfielded out, so the flatfield does not account for any vignetting and/or large scale mottling. I don't know how to work that out from the data at hand, hence the flatfield above looks uniform brightness-wise.

If someone is willing to produce a better flatfield, I'd be more than happy to see what can be done.

[machi]

This flatfield looks very promising Ugordan. Thanks!

I send one image from my "ping pong" with colors (inspirated by Elakdawalla).
This one is yet without any flatfielding

Attached thumbnail(s)

 

[Juramike]

I think having the unprocessed raw images available is necessary, while having the pre-processed PNG images available will give instant gratification. (It will be necessary to show what version utility was done to process the PNG, though)

It might be handy to have a direct link on the Mars Webcam website to the latest version of Gordan's vmc2rgb utility as well as a general article on how flatfielding is done And including a link to the lastest flatfield image version will also be neat.

[jekbradbury]

Here's an animation of some data from quite a while ago (September 2008) which is greatly improved by the flatfield. The frames are registered on the keyhole-shaped region below and to the right of the large crater in order to better show spacecraft motion.
Click to enlarge (1126x830, 2MB):

[elakdawalla]

Very well done, and an awesome animation!

[ngunn]

you are our scientists and investigators on VMC

How is that application going Doug? The image work appearing here now is astonishing and the pro/am collaboration definitely newsworthy.

[Juramike]

Digging through the archive (http://webservices.esa.int/blog/album/6/57):

Might be useful for making a dark field:
Sept 19, 2007 images: (http://webservices.esa.int/blog/album/6/298)
May 25, 2007 images: (http://webservices.esa.int/blog/album/6/121)
January 28, 2007 images: (http://webservices.esa.int/blog/album/6/108)


Might be useful for making a flat field (close-up images where features drift across field of view, more or less filling most of the view):

July 1, 2008 images: (http://webservices.esa.int/blog/album/6/217)
July 5, 2008 images: (http://webservices.esa.int/blog/album/6/222)
July 12, 2008 images: (http://webservices.esa.int/blog/album/6/225)
July 16, 2008 images: (http://webservices.esa.int/blog/album/6/227)

and June 22, 2008 (sequence animated by Fran): (http://webservices.esa.int/blog/album/6/214)

[jekbradbury]

September 2008

This was in fact the June 22, 2008 data referenced by Juramike, and September comes from me lazily using the "date modified" of the images instead of looking up the actual DoY.

[Juramike]

Here is yet another "super-resolution" attempt with the MEX-VMC image sequence taken on July 5, 2008 of Valles Marineris:

Full image corresponding to Image No. 2:


Subsection of Valles Marineris:


Even closer zoom to E edge of Candor Mensa (image scale is 1 pixel per km):


To make the super-res, each VMC image was bicubic enlarged 10x, then unsharp masked, then dropped down 50% (thus 5x). A really complex series of masks was used to allow the useful parts of the overexposed images to overlay with a darker "base" image. The images needed to be grouped carefully, since changing perspective made the overlay difficult.
(So...image 1 and 3 were overlapped with 2, while image 7 and 4 were overlapped with 6.)

It was a heckuva lot of work, and while a very slight sharpening can be seen in at the pixel level, it wasn't worth the effort.

(The final super-res image has a pixel scale of 1 km/pixel).

[Juramike]

Color study of Valles Marineris image:

[djellison]

Had a go at a few more since the flatfieldorama version of vmc2rgb (only one request - can we have a version that would work with a batch file that reads vmc2rgb.exe *.raw for example, like img2png? )

Attached File(s)

 08_291.mov ( 37.18K ) Number of downloads: 477
 08_294.mov ( 36.6K ) Number of downloads: 455

 

[elakdawalla]

I'll echo that request unless someone can tell me a quick and dirty way to run an EXE on all items within a folder...

[helvick]

CODE

for %f in (c:\temp\*.raw) do vmc2rgb.exe %f