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New Horizons Pluto System Final Approach, 28 Jun-13 Jul 15
Habukaz
post Jun 29 2015, 12:34 PM
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The SOFIA telescope is observing Pluto occultating a star today; does anyone know if results of this will be available before the Pluto encounter? It would be interesting to know if Pluto's atmosphere is still growing, remains stable or has started shrinking.

QUOTE (jgoldader @ Jun 29 2015, 12:45 AM) *
Maybe a little fun; is there a poll facility on the site? We could puree our collective brains into a jar and come up with the official unofficial UMSF list of predictions.


Another option would be to have a separate thread where members are invited to post their predictions for the Pluto system. I think it could be fun. smile.gif



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Herobrine
post Jun 29 2015, 01:22 PM
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@fred_76 At what point do those formulae cease being reasonable approximations? You have an asymptote to infinity on the day of the flyby.
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machi
post Jun 29 2015, 04:10 PM
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Pluto+Charon today, magnified 2.5.
EDIT: Added colorized version.
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fred_76
post Jun 29 2015, 04:17 PM
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QUOTE (Herobrine @ Jun 29 2015, 02:22 PM) *
@fred_76 At what point do those formulae cease being reasonable approximations? You have an asymptote to infinity on the day of the flyby.


In fact there are two things :
1) the approximation of the inverse tangente atan x ~ x because the diameter of the planet by far smaller than its distance from NH,
2) the asymptote you talk about

In practice, those formulae are quite valid until a pair of hours before "contact" as NH travels at 46500 km/h which is >> planets dia.



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Habukaz
post Jun 29 2015, 04:40 PM
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Trying to compare one of the raw images from today (rotated only first from left, rotated and interpolated scaling second from left) with two deconvoluted releases from 8 June and 15 June (respectively):

Attached Image Attached Image Attached Image Attached Image


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fred_76
post Jun 29 2015, 05:06 PM
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Nix and Hydra viewed the 29th june's bin x 1 images. Kerberos still not visible.

Attached Image



Fred


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JRehling
post Jun 29 2015, 05:42 PM
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Thanks, fred_76. This is a good way to convey the progression.

It's particularly poignant to see that 3-days-out image, because that's the best view we'll get of the anti-encounter hemisphere (AEH).

However, I'll point out that the Moon is about 1.5x the size of Pluto, so while Pluto will appear that *size*, we'll see Pluto at 1.5x the resolution that those Moon photos show. Consequently, we'll see the AEHs of Pluto and Charon at the same resolution as your left 2-days-out image of the Moon.

It's quite evident there that Tycho is a crater and one could surmise that Copernicus is. Otherwise, one could interpret the features in comparison to the better imagery of the other hemisphere, but on its own, it's still quite murky. The spectral imaging will add a lot, so that units on the AEH can be identified as likely similar to corresponding features on the encounter hemisphere.

The Charon-shine imagery may fill that in wonderfully, though, and even more important, give us a look at the winter pole that won't otherwise be seen at all.

The data set will basically be a tale of three Plutos: The encounter hemisphere, the anti-encounter daylight "hemi"sphere, and the winter pole. Similar for Charon, but we will only see its winter pole in Plutoshine from 3 days out, so we'll only get albedo/spectral information at very low resolution. On the other hand, Plutoshine is 4x brighter than Charonshine.

As a reminder of "shine" imagery, here's Iapetus in Saturnshine.
http://www.nasa.gov/mission_pages/cassini/...a/pia06168.html

Saturn is, of course, a hell of a lot bigger and brighter than Pluto or Charon, but it's also 200 times farther from Iapetus than Charon is from Pluto, so Charon occupies ~2x the area in Pluto's sky that Saturn occupies in Iapetus'. So Charonshine on Pluto is only a few times dimmer than Saturnshine on Iapetus.
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Mercure
post Jun 29 2015, 07:10 PM
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QUOTE (um3k @ Jun 28 2015, 02:48 PM) *
I was born the same year Voyager visited Neptune, so this is the first of this sort of brand-new-world flyby* in my lifetime. It's super exciting!


So you won't remember how we saw Neptune on rasterized photos in the newspaper. Earth has changed a lot since those summer days of 1989, amazingly by now letting all of us have a front-row seat to, and be part of, space exploration. Thanks UMSF!
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fred_76
post Jun 29 2015, 07:17 PM
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@JRehling : I Know the moon is bigger than Pluto, therefore I redimensionned it's image so that it has the same size as Pluto, when views from the same distance.

Now, for sure, as Pluto is certainly not made from the same materials as Moon, it's aspect will be different.


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JRehling
post Jun 29 2015, 07:53 PM
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Ah, sorry, Fred - I misread! My fault. And I'm doubly sorry, because that means the resolution will be 2/3 of what I'd thought.

The Moon seems, to me, to be unusually hard to interpret in its full phase. A lot of worlds, like Io, seem to look pretty good when full, but the Moon becomes a smear of maria, highlands, and rays. I hope Pluto is easier to make sense of in those distant, full images.
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Phil Stooke
post Jun 29 2015, 09:13 PM
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Io may look pretty good when full... but it sure wasn't easy to interpret!

I think the difficulty in interpreting the Moon at small phase angles (full or nearly so) is repeated for all worlds, notably in recent times Ceres and now Pluto. When Ceres looked twice as detailed as Pluto does today, we had interpretations of giant rifts and canyons on this very forum. Only resolution saves us.

Phil


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Bjorn Jonsson
post Jun 29 2015, 09:39 PM
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Here are the 2015-06-29 05:03 images. This is a stack of three images enlarged by a factor of 4. Two images were also obtained 6 minutes earlier that I could have added to the stack but the resolution is now probably high enough for Charon's changing position relative to Pluto to possibly have become a minor problem without correcting for it (but I notice that machi used them successfully). This image is also a 'milestone' of sorts because the size of Pluto (and the distance in pixels between Pluto and Charon) is now so big that from now on I will probably post images enlarged by a factor of 3 (or smaller) instead of 4.

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And this is Pluto with a lat/lon grid:

Attached Image


This reveals that the pole may be close to the center of terrain that is slightly darker than the terrain farther from the pole. This is a somewhat tentative result though.

Charon's shape looks slightly irregular here (and also in machi's version), probably for the same reasons that Pluto looked slightly irregular at lower resolution (Pluto now appears perfectly spherical).


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machi
post Jun 29 2015, 09:56 PM
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Here is slightly improved version. It's now made from 5 stacked images (previous was made from 4) and it's corrected for Charon's motion so Charon is now sharper.
BTW, darker area around Pluto's pole is almost certainly real feature because it's visible also in previous set from 28. June.
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jgoldader
post Jun 29 2015, 10:41 PM
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These last few images remind me of Titan, sans atmosphere.
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Daniele_bianchin...
post Jun 30 2015, 12:11 AM
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QUOTE (jgoldader @ Jun 29 2015, 11:41 PM) *
These last few images remind me of Titan, sans atmosphere.


Probably-stupid quedtion, There are possibilty that the Black Long feature are a metane or azote liquid lake?
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