I took the code I wrote to get the value vs radius combined plots of the 2 full-disk backlit LORRI shots and applied it to the 3 partial-disk backlit LORRI shots (lor_029920671, lor_0299206715, lor_0299206716). These are much closer but also much lower quality.
Data from 550,016 pixels across the three images are plotted here. This covers 8.6 times the number of pixels from the other one I posted, and at a much better spatial resolution, so the plot is much richer.
Click to view attachment
The horizontal axis is the pixel's distance from Pluto's center (left edge is 600 pixels; right edge is 740 pixels).
The vertical axis is the pixel's sample value (bottom edge is 88; top edge is (just below) 256). The sample values of the first two LORRI shots were scaled to match the brightness scaling of lor_0299206716.
All apparent large-scale contours/concentrations apparent here were also apparent in each frame's data individually; they were very consistent.
Artefacts near the bottom are from value-stepping in the original low-quality JPEG data.

Here's the same data plotted the same way, but with each point rendered with a hue based on the pixel's angle from the center of Pluto.
Click to view attachment
I had to write a different program to make this, and didn't bother with subpixel rendering. Instead, each pixel's data was written into a 560x256 array of lists (2-D binned, in other words) and each list of data was averaged to yield the pixel value. It was then scaled to 280x256 and cropped.

While I was at it, I took some of my new code and rewrote a much better atmosphere unwrapper that's binned and processes each pixel in the images exactly once and so isn't susceptible to a lot of the artefacts that turn up with resampling. I also applied an array column-averaged correction to the sample values of the radius vs angle data before rendering to compensate for the uneven lighting around the disk.
Click to view attachment
The bottom edge is the surface of the planet; the top edge is 78 pixels above the surface.
The left edge is an angle of 178 degrees; the right edge is an angle of 288 degrees (I might have that backwards...and you might need to subtract them from 360...)
The above version has been contrast-enhanced. The original output is below.
Click to view attachment

I don't know . I simply added a light source with brightness=0.25 (typically the brightness of light sources is between 0 and 1). If I remember correctly, Gennady worked out the approximate true brightness of Charonshine a few days ago.


Yes, I'm using the same set of parameters for almost everything throughout the animation. The only "cheat" is that I altered Pluto's phase function to make it brighter at high phase angles.


This is true if the JPGs are not contrast stretched (and I don't think they are but I'm not 100% sure). The scattered light is remarkably bright.


Here is a quick and dirty test render using the parameters used in the animation. The altitude above Pluto's surface is 200 meters and the field of view is 60 degrees. This should give a very crude idea of what Pluto's sky might look like.

Click to view attachment

Cool, thanks for that!

About the stretching, you can see clear signs of stretching in some images, eg this Charon image:
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x632_sci_3.jpg
Not only is banding visible by eye and the black regions quite bright, but the histogram shows discrete pixel values, indicating a stretch of about 4:1:
Click to view attachment
For this post-enc image:
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x632_sci_3.jpg
The histogram also indicates stretching, though not as severe (about 3:1):
Click to view attachment
But for this post-enc image:
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_2.jpg
There is no sign of stretching:
Click to view attachment
(Though of course jpegging post-stretch could reduce the signs somewhat.)

We can preliminary estimate stretching with assessment of the background stars magnitude, if they identify ...
I can evaluate the equatorial grid and put it into the frames...
By the way! We can try to measure the parallax of stars in comparison with images from the Earth. But only for stars closer than 50 pc

In my simulation I used the next gains table (stretching):
lor_0298996664_0x630_sci_2 = 1.5 ....... lor_0298996694_0x630_sci_2 = 1.5 ....... lor_0298996724_0x630_sci_1 = 1.5
lor_0298996974_0x630_sci_1 = 1.0 ....... lor_0298997004_0x630_sci_1 = 1.0 ....... lor_0299075349_0x632_sci_1 = 1.0
lor_0299123689_0x632_sci_3 = 0.85 ...... lor_0299124574_0x632_sci_1 = 0.95 ...... lor_0299135299_0x632_sci_3 = 1.0
lor_0299135484_0x632_sci_3 = 1.0 ....... lor_0299147641_0x632_sci_3 = 1.0 ....... lor_0299148119_0x632_sci_3 = 0.8
lor_0299148167_0x632_sci_3 = 1.0 ....... lor_0299148215_0x632_sci_3 = 0.75 ...... lor_0299148263_0x632_sci_3 = 0.7
lor_0299165499_0x632_sci_3 = 1.0 ....... lor_0299165548_0x632_sci_3 = 1.0 ....... lor_0299165597_0x632_sci_3 = 1.0
lor_0299165646_0x632_sci_3 = 1.0 ....... lor_0299165695_0x632_sci_3 = 1.0 ....... lor_0299165744_0x632_sci_3 = 1.0
lor_0299174665_0x632_sci_3 = 1.0 ....... lor_0299174713_0x632_sci_5 = 0.8 ....... lor_0299174857_0x632_sci_3 = 0.8
lor_0299174905_0x632_sci_8 = 1.0 ....... lor_0299174953_0x632_sci_3 = 1.7 ....... lor_0299175097_0x632_sci_3 = 1.8
lor_0299175145_0x632_sci_7 = 1.3 ....... lor_0299175604_0x632_sci_3 = 4.0 ....... lor_0299175721_0x632_sci_3 = 4.0
lor_0299175838_0x632_sci_3 = 4.0 ....... lor_0299206714_0x632_sci_3 = 3.0 ....... lor_0299206715_0x632_sci_3 = 3.0
lor_0299206716_0x632_sci_3 = 3.0 ....... lor_0299323619_0x630_sci_2 = 1.0 ....... lor_0299323649_0x630_sci_2 = 1.0
lor_0299323899_0x630_sci_2 = 10 ........ lor_0299323929_0x630_sci_2 = 10 ........ lor_0299324179_0x630_sci_2 = 1.0

In the case of lor_0299323899_0x630_sci_2 stretching may have been produced in 12-bit representation, so no effect on the histogram. (Possible there is stretching in 16 times, so 4 bit were cut)
High background noise and at least 7 visible stars favor this supposition.

I calculate the average over the angle values of haze brightness in dependance on the height above the Pluto surface on lit side limb (on the illuminated side the haze glow is practically independent from angle).
Such calculation I made for the original LORRI images and for simulated pictures. Also I estimate PSF of LORRI from far Pluto snapshots (it can be verified from the images of Charon and other satellites).
Now I take PSF as radial function exp(-r*r/1.44)+0.0008*exp(-r*r/100) divaded by norm.

You can get the results in
ftp://gionov:NG@46.45.15.20/_Data/_LORRI/Haze/

For example:
Click to view attachment Click to view attachment Click to view attachment Click to view attachment
Click to view attachment Click to view attachment Click to view attachment Click to view attachment
For simulate of haze I used scale 48 km, Rayleigh scale is 60 km.


It can be seen that only on the distant image lor_0298996664_0x630_sci_2 haze glowing a little less than light scattering inside the optics.
The picture lor_0299148263_0x632_sci_3_Haze shows appear as the effect of scattering near the limb, and haze glowing far away from the limb.

It's not clear that a psf measured from distant images would capture well the actual scattered light in the optical system in the near shots. Which far shots did you use?

Generally, there's going to be a strong degeneracy between optical system scattered light and atmosphere, so I think it would be very hard to reliably distinguish the atmosphere.

Mainly I used lor_0298996664_0x630_sci_2 and lor_0299148263_0x632_sci_3, and visual compare a bluring effect with original images.


On *714-716, *899, *929 frames optical system scattered light is negligible, so we can get haze scale and optical depth from this images.
Atmospheric effects on the day lit images remains ambiguous only due to the particle phase function.

Yes, absolutely, I meant it will be hard to distinguish the atmosphere on the pre-encounter images.

New simulation shows New Horizons as it went into orbit around Pluto https://youtu.be/zB4Ypa3-T_E
Glowing of the atmosphere too much to make it difficult the observation of the Pluto surface at Charonshine...
Click to view attachment

Most remarkable simulations with the atmospheric scattering and all. Is it that the atmosphere is actually "glowing" right at the location of the Charonshine, or simply bright nearby with concerns about scattering in the camera optics?

Is the bright spot on the dark side signifying anything or some type of ghost image effect?

I think that here we have not yet seen the Charonshine - it will be seen well on the next turn virtual NH around Pluto (I try increase gain parameter when NH will be opposite to Sun). Scattering by optics plays an important role, but there all the same basically own atmospheric glow.
At the end animation moment about half of the Pluto disc are illuminated by Sun from right side.
Spot on the top is Nix.


This is simulation bug at the southern pole point.
I'm fixed it just now!

Thanks for the update - I now can see the mini-moon at the very end. With the atmospheric glow on the night side, I wonder if/how multiple scattering is being considered, as that would extend the nighttime area of glow.

It's the same bug. At one point, I added a small constant 1e-6 to avoid scratch. But she was not so small, and led to diffuse faint glow of the night-side, thickening to the pole.
Multiple scattering does not considired.
New version:
https://youtu.be/8d9hR22SdZo
Version 2: https://youtu.be/Fs9qq3gnAew
Charonshine:
Click to view attachment

CharonSet:
Click to view attachment

In case anyone missed it, the 29 June stellar occultation by Pluto yielded an atmospheric pressure of 22 microbars; more than 4 times the 5 microbar pressure found by NH.

This suggests that the atmosphere of Pluto was still growing when NH flew past, although, evidently, some model somewhere is wonky.



http://www.nature.com/news/pluto-snow-fore...nundrum-1.18274

The press release caption for PIA19880 says we may be seeing crepuscular rays in the terminator region. I've done a very quick and dirty attempt to enhance that detail. Here's the original frame with gamma tweak:
Click to view attachment
I created a simple circularly symmetric template to subtract from the image, followed by stretching, to bring out the detail in question:
Click to view attachment
Some of that detail, eg the brightening at the innermost part of the terminator region, is due to processing - a mismatch between the radial profile of the template and the actual image. I'm sure you could do much better with a better template (in particular one that has an elliptical inner boundary).

But the horizontal streaks should be really on the frame. The question is are they on Pluto or not. If you look closely at the lor jpegs, you can see faint striping more or less parallel to these features, apparently due to CCD noise/dark current. This is a stack of those four frames, and shows those CCD streaks running horizontally across the dark disk:
Click to view attachment
If you compare this image with the enhanced one, you can see that some of the terminator streaks may be due to these CCD streaks - they line up - but not all. So I suspect we really are seeing crepuscular rays. Another bit of evidence is that the streaking is not visible at the outermost radius of the atmosphere.

It's bad luck that the CCD streaks lined up with the solar direction. Perhaps there will be more frames where that's not the case.

Hello!

Yesterday night I tried to surimpose a view of the "day" side of Pluto with a composite stacking of the 4 images of atmosphere's view taken the 15th july. Here is the result:

Click to view attachment
This image is "just for fun" indeed...


The correct image is the following one. It is made from the 4 full disk atmo images. The processing is as follows :
- registration on one star
- registration of the whole dwarf planet
- stacking with min/max rejection
- richardson-lucy deconvolution
- log view

Click to view attachment

The multiple layers structure of the atmosphere is quite intrigating. The dynamic of that structure should be very interesting to understand.

Fred

That would be interesting to see if a good enough shape model can be developed to simulate these crepuscular rays. It seems that obvious rays would need the mountain height to be somewhat approaching the scale height of the haze, otherwise the contrast would be low.

I have simulated these with my software geared for Earth - I wonder if this could retooled for Pluto...

My attempt to 'unwrap' the hi-phase angle images, with a hint of color added for artistic purposes:

http://s8.postimg.org/qbg9kqhmb/Pluto_Rays_COLOR.png

Looks like ninjas are nearby, but here's an unwrapping of lor_0299236719, lor_0299236749, lor_0299236779, and lor_0299236809. No correction for distortion was performed. A minor level adjustment was performed on some frames to make the brightness curve consistent across all frames. According to the metadata, there was a 0.16% difference in distance-to-target between the first and last frames, amounting to over a pixel of difference in Pluto's diameter, so each image was scaled based on the distance-to-target value in the metadata to correct for this. Alignment was manual, done at 4x scale to allow for some sub-pixel precision. Dimensions scaled-to were 4096, 4098, 4100, and 4103, from nearest to farthest. After alignment, Pluto center was estimated with reasonable confidence that the estimate was within 1 pixel of center at the original scale. The scaled frames were cropped to the region they all shared, yielding a set of 3829x4032 images, which were lightly sharpened with a simple unsharp masking algorithm with radius 6 (1.5 at the original scale) in lieu of deconvolution (because I'm lazy), after which each pixel from each of the four resulting frames (61,754,112 samples in all) was measured for distance from estimated Pluto center and angle from +X relative to Pluto center, and then 2-dimensionally binned in 1 pixel scaled radius x 0.1 degree angle bins (lists of integer sample values, actually, which were later averaged to a floating-point value). The 4000(only 2914 used)x3600 bins were rendered to a 3600x4000 image, which was then cropped to 3600x1748 (to remove incomplete radius space high above the planet), horizontally shifted 25% to place the limb-bound section near the center, gamma-adjusted, and finally scaled to half size (1800x874) to be small enough to upload here.
Click to view attachment
The horizontal axis spans 360 degrees around the center of the planet, with each horizontal pixel equaling 0.2 degrees. The vertical axis is image-space distance from the center of the planet, with each vertical pixel equaling 0.5 pixels at the scale of lor_0299236719. The bottom of the image is the estimated center of Pluto. Artefacts near the bottom are the result of a shortage of pixels for binning at different angles very near the center. Pluto average radius appears to be about 618 pixels (314 pixels at the scale of lor_0299236719).

Here's a sharpened, level-adjusted, cropped, shifted, and scaled version, including just the limb/terminator and surrounding bright areas.
Click to view attachment

Just occurred to me that tiny temperature differences on Pluto that might be enought to drive weather
Those amazing terminator images may have caught "sideways thunderstorms" convecting heat from the days side to the night side.

First bizzare concept - Pluto's N2 ices and N2 atmosphere create a planet-wide equal temperature/pressure bath.
Think of a giant pitcher of ice water, melting or freezing water in a pitcher of ice water does not change the system temperature until all the water is in one phase. N2 ice and N2 atmosphere should be a solid-fluid constant pressure/temperature system.
I've read papers that say Pluto's N2 atmospher and N2 ices should form a contant temperature system, or a constant pressure system , but that idea just sunk in- you literally can not heat up local patches of N2 ice on pluto, it just moves somewhere else, so that all N2 ice on Pluto should be at the same temperature. Instead, you end up heaing up or cooling down ALL surface N2 ice of Pluto. It's sort of a thermodynamic verision of "sea level" on earth.

Second bizzare concept- Tiny variations in heating/sublimation might drive amazing storms in Pluto's atmosphere.
On Earth, a 1% difference in atmospheric pressure creates a high or low pressure system. A 5% difference is a hurricane, a 10% difference is a tornado. Estimates for Pluto are a 1K temp increase doubles the N2 vapor pressure. Wow, a 1K temperature increase creates a 100% pressure difference. So, something as tiny as a .025 K increase in temperature due to relflected light from Charon, might create a 2.5% atmospheric pressure difference- that percentage difference on earth is sufficient to drive a tropical storm.

Some topography o the limb visible in these

http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_3.jpg
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_3.jpg
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_4.jpg
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_3.jpg

That was my calculation for the case when there is no atmosphere. Pluto atmosphere is the thermostat and it is necessary find a flow of nitrogen which compensate the additional heat from Charon. The heat flux is 5.67e-8 * 0.0256 * 4 * 40 * 40 * 40 = 0.37 mW / m^2. At nitrogen evaporation heat 200 kJ / kg, this gives 1.9e-9 kg / s / m^2. If the heated area have radius of 300 km we get 530 kg / s. At the same time across the cylindrical surface nitrogen flow was 0.3 g / sec / m. At a pressure of 1 Pa it is about 1.7 kg per square meter of nitrogen accounted, so the speed of the wind caused by light of Charon be only about 0.2 mm / s. It is negligible!

The weekly SOC release was about 90 minutes ago. 8 LORRI images were released.
Below is the full list of new images. They are all part of "P_MULTI_DEP_LONG_1_L1" and show a backlit Pluto with atmosphere/haze illuminated.
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_3.jpg
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_3.jpg
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_3.jpg
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_3.jpg
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_3.jpg
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_3.jpg
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_4.jpg
http://pluto.jhuapl.edu/soc/Pluto-Encounte...0x630_sci_4.jpg

Tried stacking them to see if I could bring out any detail that wasn't immediately near the limb. No luck.

Quote from a recent NASA article



https://blogs.nasa.gov/pluto/2015/09/25/pluto-at-twilight/

Those hazes are *blue*
http://pluto.jhuapl.edu/News-Center/News-A...p?page=20151008

And how blue they are

Such a simple image - there's not really much to comment about it from a scientific standpoint. But it really packs an emotive punch. Each time I look at that picture it makes me think, "why the heck haven't we visited this world sooner" and "wow, what else is out there in the kuiper belt?"

And it vindicates the wonderful coloured version of the looking back landscape posted here earlier.

http://www.unmannedspaceflight.com/index.p...st&id=37888
I'm so relieved - I so much wanted to believe that scene was real but couldn't for sure till now.

The blue color is interesting because it *may* mean that Mie scattering isn't as dominant as would have been case had the atmosphere been grayish (or not blue). Which in turn may mean that the atmosphere might be easier to see in low-phase views of Pluto. If I remember correctly, someone (Gennady maybe) had noticed what could be atmosheric limb hazes in low-phase LORRI images but it could also be due to scattered light - what's really needed are higher resolution low-phase images of Pluto's limb to distinguish possible hazes from scattering in LORRI's optics.

Interesting about the blue color. We can consider this in quantitative terms as to what the Angstrom Exponent would be. Typical aerosols on Earth range from 0-2 (gray to light blue). Air molecules are a value of 4 (more blue). What Bjorn is mentioning would be consistent as the smaller aerosols, having the higher Angstrom Exponent, would also have a flatter phase function with less brightness difference between forward and backward scattering. Thus the color can be correlated with both the size and with the phase function.

Though note that that fractal particles, such as found on Titan, can have a pretty high Angstrom coefficient AND are pretty forward-scattering.

If anything, I was *too* conservative with the saturation of the blue hazes!

Yes perhaps it should be bluer. I suppose we can sample the released RGB image and consider the color ratios, color space, tristimulus functions, gamma correction, and wavelengths of interest and even calculate the Angstrom Exponent.

In hindsight this test render I posted 2 months ago is interesting:

http://www.unmannedspaceflight.com/index.p...st&p=225265

Not quite saturated enough since judging from the description I've seen of how the MVIC image was processed it should be very close to the true color and contrast of Pluto's atmosphere.

Yes, and I used "flat" phase function with forward/backward ratio equal to 6.
With regard to the published picture, I was confused by the fact that the color of a narrow crescent of reddish surface of Pluto are also blue.
Slightly corrected the color and get this:
Click to view attachment

I think you both (Ian and Bjorn) were absolutely spot on with the colour. Colour saturation is a subjective physiological thing. When you look at the NH image the blue atmosphere occupies a very small fraction of your field of view. It looks strikingly blue, but if you actually went there so your whole sky in the direction of the sun was filled with it it would seem less so.

How narrow? Is the sunlit surface actually resolved, or are we just seeing mainly the brightest part of the sky (ie the largest phase angle part)? We may not expect to see any red if the sunlit surface is very narrow. Knowing the time the image was taken, it should be easy to simulate the view from NH and determine how many pixels (or what fraction of a pixel) the sunlit suface is wide.

Also, there will be some atmosphere "on top of" the sunlit surface adding blue light to the surface's reddish light (as much as half the optical depth of the pure-atmosphere lines of sight). Distant mountains on earth tend to look blue for this reason.

I can simulate what portion of pixel crescent is sunlight reflected from the surface from the total brightness of the pixel, if it is known shooting time. But using previous experience of modeling LORRI images I can say that it is about 90%.

However, it is possible to analyze other more simple and reliable way without simulation of light tracing.
Unfold the image relative to the horizon
Click to view attachment
and find the dependence of the maximum brightness for each color channel from the position angle
Click to view attachment
blue channel overexposed in crescent region, but it does not hurt much to our analysis.
Night side takes an angle of approximately 155 to 335 degrees.
At this angles atmospheric glow reaches its maximum value and almost no change in the crescent. Thus the excess glow is associated with reflection from the surface of Pluto.
On the night side of the weakening of glow due to the fact that we see illuminated the higher layers of haze. Multiply colors on the night side by constant factors, so that at the border with crescent values in channels about the same.
Click to view attachment
Either the color of haze becomes more blue with height or the image have shifted zero at blue channel.
The color of the reflective surface is obtained as on the left side of picture, in the middle is avarage color of pluto surface:
Click to view attachment

If we multiply the green channel by 0.9, and blue channel by 0.8, we get the color of the surface of Pluto as on the right part of picture:
Click to view attachment
RGB graph:
Click to view attachment
And corrected image in comparing to original:
Click to view attachment Click to view attachment

I thought it would be interesting to compare simulated blue skies on Earth using my ray tracing software to what we see on Pluto. In a rather clean atmosphere case, I show Earth skies to have a G/B ratio of about .71. This is after converting the radiances to an RGB image for display. Meanwhile the released image has a somewhat variable G/B ratio from roughly 0.68 to 0.81. I wonder why this ratio should vary with the intensity if all of the color balancing is done correctly? Nonetheless if we take a "typical" value in the released image of .76 this would work out to an Angstrom Exponent of about 3.3. This is on a par with the bluest of hazes we see on Earth though not quite a pure Rayleigh scattering value of 4.

If the vertical color gradient in the released image is real, then we might surmise the Angstrom Exponent increases with altitude and the aerosol particle size also decreases with altitude.

It's completely unclear what you're saying here. On the night side, as I think you say, we're seeing pure atmosphere and no sunlit crescent. On the day side we're seeing atmosphere plus thin sunlit crescent.

But, as I think you also say, the atmosphere we see on the night side is typically higher than the atmosphere we see on the day side. The low-elevation atmosphere is in the shadow of Pluto on the night side. But on the day side we can see the atmosphere right down to the surface of Pluto. This means that, even if the suface of Pluto was perfectly black, we'd expect the day side atmospheric glow to appear brighter than the night side glow!

Of course Pluto is not black and there will also be a contribution to the day side from the thin sunlit crescent. But here's the key point: in the absence of modeling, we don't know how much of the excess brightness between night and day is due to the fact that we see lower atmosphere on the dayside, and how much is due to the fact that we also see sunlit crescent on the dayside! In other words, we don't know how much the sunlit surface contributes to the day side brightness, so we can't set colours according to the average surface colour!

In addition, as scalbers pointed out, the day-night colour differences you're seeing may simply be due to the atmosphere being bluer higher up, which is consistent with small particles clumping into larger particles as they fall, as we'd expect. Or they may be due to nonlinearity of the RGB levels, due maybe to gamma adjustment.

To sum up, we have no reason to mistrust the image we've been given and nothing upon which to base a quantitative adjustment of it.

That's largely true though I'd be interested to refine the assessment of the maximum blueness in the upper atmosphere. The image drops to a G/B ratio of around 0.6 in the top and faint part. In theory it should stay above about 0.70 at least from my various assumptions.

Yes, it is obvious that the night side is darker than day side. I tryed to say that in the case of the black surface of Pluto on the day side will be almost constant brightness. And the deviation from a constant glow is caused by the surface, which is due to the optical blur mixed to atmospheric glow. So it can be used of caliberate of color chanels.

Yes, if we multiply blue channel by 0.8 than the result will be more consistent with the theory.

Do you mean constant brightness as a function of position angle around the disk, on the day side? I don't see why that should be constant. The phase function should peak at the largest phase angles, so the atmosphere should be fainter towards the ends of the day side. (Of course the important question is how fast the phase function drops, which is model-dependent.)

This could be easily checked by rendering the atmosphere with a black surface, keeping in mind that we don't know the phase function so a range of possibilities should be considered.

Yes! Exactly!

If distance at the shooting time was about 50,000 km, the change in the scattering angle was about 1 degrees with an angle value about 15 degrees. The reason I say that is ALMOST constant.


I try to do it for MVIC:
Click to view attachment
Distance to Pluto is 175000 km. Take image time is 15:21:30 UTC July 14 if original image does not scaled.

If we turn on surface with map http://laps.noaa.gov/albers/sos/pluto/pluto_rgb_cyl_16k.png
we obtain
Click to view attachment
To comparing original MVIC image and with multiplied blue by 0.8 and green by 0.9:
Click to view attachment Click to view attachment

A tweet from the Pluto session at the DPS meeting: Hayley Williamson ‏@hayleynw92 :

"Pluto haze is probably aggregate particles to allow for blue color (small particles) and forward scattering (large particles). #DPS15"
Basically follows the discussion here.

http://spacenews.com/new-horizons-reveals-...es-about-pluto/

On an AGU poster I recall something like a .0045 optical thickness (tau) for the haze with a scale height of ~50km. It's interesting to note this tau is similar to what we see on Earth for stratospheric aerosols when they are enhanced somewhat due to volcanic emissions (such as presently). This relates to the brightness of twilight on Earth about 25-30 minutes after sunset.

When we're talking about "strong" forward scattering, I wonder what the peak of the phase function is for a scattering angle of zero degrees (180 phase angle)? The phase function is a quantity that integrates to 1 over the sphere. For the analogous atmosphere of Titan, this function is shown in figures 12.20 and 12.21 here: http://www.ciclops.org/media/sp/2010/6514_15623_0.pdf. Scaling factors are used in the figures to help separate the individual plots. The peak is thus nearly 1000. This indeed is what we'd see on Earth for pretty large particles in the haze, as would happen in a dusty day with a condensed bright aureole around the sun with around half of the scattered light contained in just a few degrees of radius.