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Radar And Mariner 10, Best possible mapping, pre-Messenger
t_oner
post Dec 8 2007, 10:17 AM
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Hi gcecil, thanks for the map but it seems to have some serious scale problems, Mariner 10 data covers more longitudes than it should. I think there was a mistake in compositing.
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edstrick
post Dec 8 2007, 11:46 AM
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Mariner 10 took a series of approach <crescent> data for something like 6 days and outgoing data for maybe 3. Granted, the furthest out data is pretty horribly low rez, but the data shows stuff beyond the terminator on both approach and flyout. That's how the large crater "Mozart", south of Caloris, was discovered. It's not in the high rez mosaics.

Some of the data was lost or truncated by camera wander due to Mariner's large attitude control slop, and I vaguely recall some color band data may have been smeared by the wander, or some data was over-exposed, but I've always wanted to see the several frame zoom "movie" from approach and flyout, both at native resolution, and rescaled to a uniform diameter.
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t_oner
post Dec 8 2007, 12:13 PM
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I am not sure if edstrick's post is an answer to my post but let me make it clear: Mariner 10 high res data covers 190 to 10 degrees longitude, not 190 to -10 as in gcecil's map. That map has a scale problem.
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gcecil
post Dec 8 2007, 01:19 PM
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QUOTE (Tayfun Íner @ Dec 8 2007, 07:13 AM) *
I am not sure if edstrick's post is an answer to my post but let me make it clear: Mariner 10 high res data covers 190 to 10 degrees longitude, not 190 to -10 as in gcecil's map. That map has a scale problem.


Yup, scale was messed up when I cutoff at +/-70 lat. Fixed now, so reposting with proper format. Thank you!

This map
Attached Image
(full res image here) includes recent (reported within last 2 wks) amateur imaging (290-360 deg) by John Boudreau and our SOAR telescope imaging from earlier in the yr (185-290 deg), only to +-70 deg lat shown. Hints of topography near the terminator in our data (e.g. other half of Mozart), elsewhere mostly bright rayed radar craters. Alignment along longitudes of bright features is an artifact of the phase correction. Agreement with rayed radar craters (and their diameters) is given in our paper.
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t_oner
post Dec 8 2007, 02:35 PM
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Here is Version 3 with optical data added from Baumgardner et al. Cosmetically corrected for Celestia.
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edstrick
post Dec 9 2007, 10:11 AM
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I didn't spot the scale problem, I was just pointing that to some extend, Mariner 10 converage extends beyond the high-rez mosaic's terminations at the terminators.

Did Mariner really say "I'll be back!"?
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tedstryk
post Dec 14 2007, 03:56 AM
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Here is an example of a Mariner set that shows a bit beyond what the high resolution images show. This is the same set of images, processed to look relatively natural on the left and with heavy high-pass filtering on the right.

Attached Image


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peter59
post Dec 30 2007, 09:13 AM
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I recognize that many of you are waiting for new images of Mercury, but you can't also see old images.

Attached Image

Tape MVE_033 Image 091 (29 November 1973)


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Free software for planetary science (including Cassini Image Viewer).
http://members.tripod.com/petermasek/marinerall.html
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tedstryk
post Jan 4 2008, 09:55 PM
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I have been playing around with some Mariner-10 shots. I experimented with color, but Mariner 10's camera had such a weird filter selection that, when combined with calibration issues, make things really difficult.

Attached Image


Here is a cleaner view of the south polar view I did a while back, both in original form and from a high pass filter. There is a larger mosaic, but since it depends on a heavy amount of reprojection, I decided to stick with the wide angle data, as Mercury's topography makes significant reprojection obvious.

Attached Image


Here is the 3rd encounter Discovery Rupes mosaic, with a small gapfill from stacked first-encounter images to fill the sliver between the two lower images. Also, I did a stack of the "Discovery Dome" area using third encounter images.

Attached Image


Attached Image


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JRehling
post Jan 4 2008, 10:41 PM
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[...]
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tedstryk
post Jan 4 2008, 10:44 PM
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True-color is such a relative thing....I think even Messenger stuff might go through a few variations as we have seen in color images from many early missions....the problem is the lack of a standard for subtle balancing work. By the way, if anyone downloaded the image right after I posted it, I posted the wrong file...it has now been corrected.


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JRehling
post Jan 4 2008, 10:57 PM
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[...]
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tedstryk
post Jan 5 2008, 12:04 AM
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What I am trying to say is that it might take a while before images can be calibrated to the point of providing color of the quality of, for example, Cassini images. For the other planets, we at least have good earthbased color data. Mercury images, on the other hand, are so damaged by atmospheric refraction and (in daylight) scattered sunlight that they don't provide much of a reference point. In other words, I can see the color images being produced two years from now looking very different from the ones we will see in the next few weeks.

Incidentally, Mariner 10, while having odd filters, had a great camera, but unfortunately, as has been mentioned before, the camera pointing resembles footage from an drunken camera man. That makes the images very hard to assemble, especially using color. I always wondered why Mark Robinson and his team only produced a color ratio map of a small area. After trying to work with the data, I understand.


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ugordan
post Jan 5 2008, 12:42 AM
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I personally think any color uncertainties in the first images will be smaller than any comparative "ground-truth" later, onboard spectrometer corrections will suggest. Mercury, after all, isn't likely to be a very spectrally complex place like Jupiter, Io or Saturn. It will probably have gentle spectral slopes and that's where even discrete filter MDIS composites can come very close in "true color" to what a more precise integration through many spectral wavelengths (approximating the actual spectral curve to a good degree) would give. Messenger carries a spectrometer, although apparently not an imaging one. MASCS will probably be good enough anyway, just like Cassini's VIMS can be used at Saturn.
The MER rovers don't have that kind of training tool and all their surface "true" color views are basically generated on the basis of being the most probable result of solving some integral equations IIRC.

I'd like to know if Cassini image products were trained on groundbased imagery (I know my first reactions to the first Saturn color shots were how different it looks than from other earthbased views I saw) because the vantage points were different and direct color calibration would be difficult due to phase angle effects etc. There is certainly variation in color results even today from CICLOPS image releases, although less than before. I'm saying that with good spectrometers onboard you don't even need groundbased observations for good color quality and this might very well turn out to be the case with Mercury.

Color me happy if Mercury doesn't turn out as spectrally grey as our own Moon. Even a brownish hue is some personality.


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tedstryk
post Jan 5 2008, 01:20 AM
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I think the lack of color is the problem. With color variations being so faint, balancing is made very difficult. For "natural" views, this may be only subtly visible, but it may effect the warm/cool color appearance, which is why I say there may be a lot of variation at first (it really depends just what color Mercury really is to see whether this materializes). I have never thought it too terribly important to replicate the human eye in planetary images - the RGB response of our eyes is so arbitrary for planetary targets that unless we are generating graphics for astronaut training, using other wavelengths that better highlight a world's compositional variations is a great technique. However the Mariner 10 filters set is just weird. It does have a dedicated yellow filter, but it was seldom (if ever) used. There is so much overlap between the filters used here (UV = blue, blue = green, and "minus UV" = red) that isolating three channels is quite treacherous.

On a more abstract level, I often wonder how much variation there is between different sets of eyes. I have gotten into long debates with people who are looking through my telescope and could swear it has a cool hue while others swear it has a warm hue. I have noticed that on many nights, it looks cool in my left eye and warm in my right eye. Perhaps this is what gives me my opinion on color.


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