Mercury Flyby 1 Options

[edstrick]

"...While we are waiting, here is my incoming mosaic..."

Thanks !!!
That's a view I've been waiting for for 33+ years

The Mariner 10 cam was pretty good, but it's decalibration left a lot to be desired, partly because of comp limitations at the time.

The thing that really was sucky was the color filter set. I never saw a really clear explanation of what they picked and why it was so bad on it's primary target. Mariner 9 at Mars had an excellent set of filters: Red, Green, Blue and Violet for the color set, similarly shaped medium-wide spectral bands with little overlap should have given a good first look at Martian multispectral patterns. But the camera was uncalibratable due to residual image (damn near) and then the filter wheel stuck on an orange-polarizing passband and THEN the dust storm cleared. Aaaarughhhh.

[4th rock from th...]

Nice mosaic! I do like the colors, at least they are consistent, although I'm not a fan myself of Voyager like OGV ou OBV color compositions. Of couse, and having worked with the M10 data, any atempt to get "real color" out of that filter set is very difficult. I really like the overall orange-brown color, it looks real to me.

[ugordan]

Color ahoy!!!

[elakdawalla]

Woo hoo!

What do you think of that "orange-brown color," 4th rock?

--Emily

[Juramike]

Color ahoy!!!

I like the little "blue splat" at lower center of the released image:




-Mike

[ugordan]

What do you think of that "orange-brown color," 4th rock?

It looks a bit stretched to me personally.

Mike, I think we'll find all the fresh(er) craters will have blue ejecta blankets in this filter combo, this probably signifies less space weathering and... well, fresher materials. The same thing we see on icy moons, only different compositions.
I wonder how much of the blue hue is due to compositional differences (less meteoric dust in the regolith) and how much is due to crystallinity of materials? Would crystalline materials appear any bluer, anyway?

[tedstryk]

I am pleasantly surprised to see that the color, which does seem a bit stretched, matches my crescent OGV view fairly well (the one I posted last night), but my color is much more subdued.

[JRehling]

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[JRehling]

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[ugordan]

I actually think they brightened the violet frame to match the brightness of the IR frames, for the sake of pleasing appearance. I'm skeptical the blue splat actually is brighter in violet than in IR, only brighter than the rest of the planet. It'd be cool to be wrong, though, that would mean Mercury's much more colorful than our Moon.

If you look at the first MESSENGER spectrum of Mercury, you can see the sample of the "normal" surface is much dimmer in the violet portion than in the IR. The "true" color might actually turn out to be much redder/more brownish than this and the fresh ejecta might turn out to be more gray. That's my hunch at least.

If only they put some wavelength marks on that spectrum, I could run it through some CIE XYZ code and see what color that would approximate to the human eye.

Taking that spectrum and taking a rough ratio between R/B wavelengths (I get blue slightly over 80% as bright as red) and applying that to the neutral regions of Mercury (approximating the 700 nm filter brightness as red for a first iteration and taking the 430 nm violet as blue, with a synthetic green from the two) gives roughly something like this:


Ugly? Wait, that's not all. Invariably, almost all spacecraft images are displayed non-gamma corrected because that increases the contrast and color saturation. If we apply the sRGB correct gamma of 2.2 to essentially linear spacecraft data, this is the end result:


That winds up looking similar to the false color composite, only with less pronounced blue hues. It's also similar to Ted's earlier composite.
As a comparison, non-gamma-corrected imagery is usually responsible for a very brown-looking Moon seen by many spacecraft.

[4th rock from th...]

What do you think of that "orange-brown color," 4th rock?

I like it :-) The most important thing is that the brown hue (moon like but more saturated) seems consistent in M10 images, earthbased views and this Messenger image, even considering that each image was derived from very different filters. That's not completely surprising, as the planet's spectrum is close to a straight line. So you can get almost any 3 evenly spaced wavelengths and get the same global tone.

[tedstryk]

I like it :-)

Regarding your OGV or UV comments....Of course, with vidicon's red-blindness, it is often our best option. It has always bothered me more than a red/near IR shift because it tends to give fewer new interesting color feature in exchange for not being as "human." However, with some worlds, it is more bothersome that others. For example, Ganymede doesn't look too much different in properly done Voyager and Galileo color. However, Io and Europa look quite different. Mercury, with its rather flat spectral curve, appears to be more like Ganymede in its response to color shifting.

[Bill Harris]

It has been decades since I've observed Mercury through a telescope, but I'll alwasy remember it as having a warm hue: the "orange-brown" color noted upstream. Of course there is always the personal equation on the perception of "true (or actual?) color", but there is some validity to the perceived color of Mercury.

One classic example of color mis-perception is found on telescopic views of Mars. The darker albedo markings (AKA "Mare") have long been perceived to have a blue-green hue, caused by the contrast with the orange color of the adjacent lighter areas.

--Bill

[DrShank]

Ive taken the released color image and applied some simple saturation to it. some of the color differences begin to come out, including the blue crater and some orange patches. looks like there could be some interesting geologic patterns!

paul

[4th rock from th...]

Regarding your OGV or UV comments..... However, Io and Europa look quite different. ....

I agree. The only solution for working with wavelenght outside the visible (or borderline visible like violet) is some sort of colorspace convertion. This way, a OGV composite can have some "red". That "red" will come from a correct display of the violet filter into RGB space. Simply put, Violet in RGB corresponds to both the Blue and Red channel (of course mainly to the Blue, but witha significative presence in the Red).