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Phobos
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post Nov 11 2007, 09:43 PM
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peter59
post Feb 16 2008, 05:03 PM
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The High Resolution Stereo Camera (HRSC) on Mars Express is not the best instrument.

Orbit 3802, Phobos, image h3802_0003_sr2
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Orbit 3802, Phobos, image h3802_0004_sr2
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djellison
post Feb 16 2008, 05:19 PM
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HRSC itself is great, but the super resolution bolt-on camera from which those two frames came from has never achieved good focus.

Doug
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peter59
post Feb 16 2008, 06:39 PM
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Mars Express (MEX) release #2.
February 14, 2008

Online Data Volumes - Mars Express

Orbit 3310, Phobos, image h3310_0000_s22
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Orbit 3310, Phobos, image h3310_0000_s12
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peter59
post Feb 16 2008, 06:50 PM
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Another high (??) resolution image.

Orbit 3769, Phobos, image h3769_0004_sr2
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djellison
post Feb 16 2008, 09:09 PM
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QUOTE (peter59 @ Feb 16 2008, 06:50 PM) *
Another high (??) resulution image.

Orbit 3769, Phobos, image h3769_0004_sr2



The SR2 dictates it's from the super resolution camera, bolted on to HRSC, and thus suffers the same issue I mentioned previously.

Doug
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algorimancer
post Feb 16 2008, 10:57 PM
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QUOTE (djellison @ Feb 16 2008, 11:19 AM) *
...has never achieved good focus.

I tried running Helicon Focus software on a few images. Looks like a combination of motion smear + out of focus, but the dominant effect seems to be motion smear. Due to the jpeg artifacts it's a little difficult to do a good job of this, but here are some images with the motion smear (somewhat) corrected. I think that if I had uncompressed versions of the images then I could pull quite a bit of fine detail from them.

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ugordan
post Feb 16 2008, 11:13 PM
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I don't think it's motion smear, more like noncircular PSF due to out of focus deformity in some part of the optics. It gives an appearance of vertical motion smear. It would probably be possible to do a proper deconvolution if we knew the PSF exactly (say by imaging a star), but as I recall the amount of defocus isn't constant either.


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Phil Stooke
post Feb 17 2008, 01:37 AM
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It certainly is not motion smear, but it does look like it because there is a 'double exposure' effect. Regardless, they are still nice images in other respects, and are being used to improve the shape model of Phobos (The other HRSC images are less useful for that because they are from a scanning rather than framing camera). The top one just above is inside Stickney. These pics come in sets of 4 or 5 making up strips across the surface, and would make nice mosaics.


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mgrodzki
post Feb 17 2008, 03:26 AM
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peter59
post Feb 17 2008, 07:34 AM
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QUOTE (Phil Stooke @ Feb 17 2008, 02:37 AM) *
It certainly is not motion smear, but it does look like it because there is a 'double exposure' effect.


'Double exposure' effect.
Orbit 3196, Deimos, image h3196_0005_sr2.
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peter59
post Feb 17 2008, 07:46 AM
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QUOTE (Phil Stooke @ Feb 17 2008, 02:37 AM) *
These pics come in sets of 4 or 5 making up strips across the surface, and would make nice mosaics.


Orbit 3802 - images h3802_0003_sr2, h3802_0005_sr2, h3802_0005_sr2
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Orbit 3802 - image h3802_0000_s12
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algorimancer
post Feb 17 2008, 02:05 PM
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QUOTE (ugordan @ Feb 16 2008, 05:13 PM) *
I don't think it's motion smear, more like noncircular PSF...

I'll take your word on that. Incidentally, what is "PSF"?
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djellison
post Feb 17 2008, 02:51 PM
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the S12 image is pushbroom.

PSF = Point Spread Function. i.e. the contribution of surrounding pixels to the pixel in question. With accurate info on that, you can subtract it all back out again..ish...roughly.

Doug
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tedstryk
post Feb 17 2008, 06:08 PM
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Here is a quick attempt. There does seem to be motion blurring in some of the data, almost as if it is a double exposure with one of the two slightly smeared in a direction almost but not quite perpendicular to the direction of the double exposure offset.

Attached Image


Edit: The bit of motion blur I mentioned could also be explained by optics being slightly out of alignment. Normally, the difference between the two is obvious, but this is too slight for that.


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