New Horizons: Approach Phase, OpsNav - 25 January 15 to 28 June 15 Options

[Alan Stern]

Alan, is there a doc you can point to, or much you can say (without spending too much of your very valuable time!) about how fault protection is going to be handled during the period around close approach? I'd assume there is some sort of inhibition against entering safe mode for most possible faults, but maybe I'm wrong on that. Thanks!

Correct. Encounter Mode (P-7 to P=2) locks out safe hold. See papers on NH "Autonomy" system in AIAA and IEEE proceedings by Bauer et al.

[Julius]

My wild guess regarding the dark areas within the bright areas..I believe we could be seeing first signs of sublimation of ice!

[Bjorn Jonsson]

Here are two versions of an image that is a stack of four images obtained 15 seconds apart on June 6 at a range of 45.8 million km. Here they have been enlarged by a factor of four.



I used these images:

lor_0295859743_0x630_sci_1.jpg
lor_0295859728_0x630_sci_3.jpg
lor_0295859713_0x630_sci_3.jpg
lor_0295859698_0x630_sci_3.jpg

The left version is the stack without any processing so it should show correct relative brightness. The right version has been sharpened using RegiStax. The sharpened version reveals a diagonal dark band on Pluto - it's now absolutely certain that this is a real feature. In contrast, the apparently brighter terrain at the right limb is almost certainly a processing artifact. Charon may be starting to show large scale markings, i.e. possibly very slightly darker terrain in its upper left 'quadrant'. But this could easily be an image processing artifact.

The left version can be used to make crude brightness estimates. Using 1 for Pluto's brightest terrain, Charon's surface is ~0.5, the brightness of Pluto's dark 'band' is ~0.9 (not very accurate) and the darkest terrain is ~0.25 to 0.3. The dark terrain is rather close to the limb so 0.25-0.3 isn't very accurate but nevertheless this seems to indicate that even though Pluto has large albedo variations, the contrast is probably significantly less than on Iapetus.

It wouldn't surprise me if small dark spots started appearing within the bright terrain at much higher resolution and/or small bright spots started appearing within the dark terrain.

My wild guess regarding the dark areas within the bright areas..I believe we could be seeing first signs of sublimation of ice!

This seems very plausible. Also one crazy idea is that some of the dark terrain could be associated with activity of some kind, maybe like Triton's dark geysers, but it's rather early to start speculation about that. But things are starting to get really exciting now that the images are clearly better than the best HST images.

[Gerald]

This is a stacked and heavily sharpened (before and after stacking) version of three 2015-06-09 Pluto/Charon images:

I'm very skeptical about this strong sharpening. So we may see anything from processing artifacts to a giant storm on Pluto. Charon is going to show reproducible features.

Edit: Color-encoded brightness of stacked image without sharpening, to offer an alternative view:

There is a clear asymmetry of the brightness, but interpretation is partly suggested by processing.

[elakdawalla]

The intense ring around Pluto looks like over-sharpening to me. There is information in these images, but so little that it's easy to destroy with overzealous processing.

[Gerald]

This is a "faked" image as comparison, starting with no relevant features, and similar sharpening:

It's rather rotational symmetric. So deviation from the rotational symmetry in the processed original images hint towards real features. But besides the optical PSF there is an additional risk of enhancing jpg artifacts, since the processed Pluto image is a composite of only three jpg-compressed images.

[ZLD]

Heres a processed version of 'lor_0296134018_0x630_sci_1' from yesterday.



Max entropy deconvolution and some histogram functions.

[Phil Stooke]

My version of the June 9th images, the three LORRI images merged. A bright right edge on Pluto itself is an artifact of my appallingly ad-hoc processing method.

Phil

[paraisosdelsiste...]

New images taken today!


Edit: Sorry, I forgot to add the original source: http://pluto.jhuapl.edu/soc/Pluto-Encounte...sure=100%20msec

[Bjorn Jonsson]

It's very interesting to see the image together with the diagram showing the image orientation. It's starting to look as if Pluto has a bright polar cap, a somewhat darker collar around the bright polar areas and then brighter terrain in the equatorial areas - not as bright as the polar terrain though.

Close inspection of the original, unprocessed image seems to imply that the poleward (northern) edge of the collar might be more subtle and less sharply defined than the southern edge (the edge closer to the equator).

Edit: Of course other images show that *if* there is a darker collar around the bright polar terrain its extent to the south is probably nonuniform and varies with longitude.

[paraisosdelsiste...]

I've made a quick and dirty rotation movie with the LORRI frames taken the days 6, 7, 8, 9 and 10 and some features seem to be consistent between frames.

[jasedm]

It's starting to look as if Pluto has a bright polar cap, a somewhat darker collar around the bright polar areas and then brighter terrain in the equatorial areas - not as bright as the polar terrain though.

Somewhat similar to Triton...... Pluto and Triton have very closely-matched densities too. I think the case for Triton being a captured KBO may be strengthened further following the flyby of Pluto next month.

I wonder if we'll see any 'canteloupe' terrain?

[Gladstoner]

I wonder if we'll see any 'canteloupe' terrain?

Or geyser plume trails?

[JRehling]

Pluto and Triton may be very similar in terms of size and bulk constituency, but they are very different in terms of seasons: Triton maintains a scrupulously constant distance from the sun, but the sub solar latitude varies radically and non-sinusoidally. Pluto has a wide range of distance from the Sun, but everything should be very regular and periodic. This may make for a big difference in how frost or anything else pertaining to variations in illumination is distributed and/or redistributed.

The dark line seen in Bjorn's work got me thinking. Elsewhere in the solar system, what does a long, large linear (but not perfectly linear) feature indicate? Often, it's a sign of geological activity, either extension or horizontal movement. Other causes could be volatiles in motion. Another possibility is that the line is merely the negative space between other things, although this becomes unlikely if the two edges are parallel over long distances.

By and large, geological activity, past or present, is most common. That would be very exciting. But then again, Pluto might break every rule we've ever thought of.

[Bjorn Jonsson]

Looking at the possible dark collar around Pluto's pole and comparing the NH images to schematic views (rotated to match the viewing geometry) with a lat/lon grid seems to indicate that the 'collar' is located very approximately between latitudes 40 and 60 degrees north. But this is all very tentative. Even though the presence of the dark, diagonal line in the image I posted yesterday can now be considered certain (it's also seen in later and earlier images processed by me and others), the presence of a polar collar is in my opinion far from certain yet.

Pluto and Triton may be very similar in terms of size and bulk constituency, but they are very different in terms of seasons

I also have doubts about big similarities between Pluto and Triton, for one thing Pluto exhibits much bigger albedo variations than Triton at comparable resolution.