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Uranus System Imaging
scalbers
post Sep 13 2014, 09:28 PM
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Nice view Bjorn - with a polar pentagon (or maybe hexagon).


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Bjorn Jonsson
post Sep 14 2014, 12:11 AM
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I don't know if the polar pentagon/hexagon is a real feature or not but it might be real (or not...). Interestingly, it's not clearly visible in versions of these images where I don't correct for the wind speed. I'm now working on the violet filtered images. They show the areas near the pole better than the orange images do but everything else is more visible in the orange images. One of the Voyager 2 wind speed measurements is actually from violet images: The Voyager 2 measurement closest to the pole, at ~71 degrees south.

So far no results on the polar cap from the violet images, I just started processing them.
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Bjorn Jonsson
post Sep 15 2014, 11:07 PM
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Here are two versions of an image from a stack of 8 violet filtered images:

Attached Image
Attached Image


As before the left one has been processed with a combination of a contrast stretch and an unsharp mask and shows both the large scale brightness variations and small scale details although some detail is lost near the limb. The right one was processed with a high pass filter and then an extreme contrast stretch. This largely suppresses the large scale brightness variations but should show small scale features a bit better, at least in the areas near the limb that are dark in the left version.

These images are not from the same sequence of images as the orange/green stack I posted yesterday so the viewing geometry is different and Uranus has rotated around its axis between this image and the orange/green image. The source images here were obtained over a period of 5 hours from January 16 1986 19:51:10 to January 17, 1986 00:51:58.00 when Voyager 2 was 10 million km from Uranus.

The polar cap is now more obvious and this image also reveals that it is very probably circular; its vaguely pentagonal/hexagonal shape in the orange/green stacked image is probably not a real feature. There are also some hints of at least one narrow dark cloud belt a little outside of the polar cap, approximately at latitude 75 degrees south.

These images aren't exactly photogenic but despite that, this has been one of the most interesting image processing projects I have ever undertaken. Especially the orange/green stacked image shows some features I have not seen before in the Voyager 2 images of Uranus. Comparable features (plus many more) have now been imaged with far better clarity with groundbased telescopes but it's still interesting to see some of these features in these old images.

I have also been experimenting with bigger stacks but unfortunately I have now found that stacking images obtained over one Uranus rotation or more does not work well, even ~10 hours apparently does not work very well. This means that significantly bigger stacks than I have been using here are probably not possible although testing this further might be worthwhile.
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MarcF
post Sep 30 2014, 09:30 PM
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Wow really nice Bjorn.
The latest Keck Observatory pictures of Uranus (August 2014) show massive storms:



Link to Keck Observatory
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Bjorn Jonsson
post Nov 8 2014, 07:35 PM
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Uranus once looked dull but it really isn't - it's a very interesting planet. The problem is the thick hazes which make any features difficult to observe unless infrared imaging is used. There really is a lot of activity there and I'm starting to get the impression that if you count the number of active-looking features, storms, bright and dark spots etc. it might actually be more active than Neptune. I'm no expert here though so take this with a grain of salt (but it would be interesting to know if this is true).

But it turns out that the big, bright feature visible in the right image above is actually the biggest storm ever observed on Uranus, see e.g. here and here. In fact it's so big that it has been imaged by amateur astronomers. A movie by Anthony Wesley can be seen here:

http://www.acquerra.com.au/astro/gallery/o...-storm-anim.gif

And his gallery of Uranus images is well worth visiting (other targets can also be seen at his website):

http://www.acquerra.com.au/astro/gallery/other/index.live

In addition, HST observed the storm in mid-October but as far as I know the images haven't appeared anywhere yet. It will be interesting to see them.

And here is an enhanced version of the images above. I processed it to reveal small scale features more clearly :

Attached Image
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Stefan
post Nov 15 2014, 01:02 PM
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Voyager image processing magic by Erich Karkoschka:

http://uanews.org/story/clues-revealed-abo...erior-of-uranus
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MarcF
post Nov 16 2014, 03:37 PM
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Wow, just great. My favorite planet looks better and better.
By comparing these enhanced Voyager pictures with the Keck pictures, we can see that the southern hemisphere did not change much since 1986.
The wide and the narrow bright bands are present in both sets of pictures, with storms between them.
The narrow dark band close to the wide bright one is also present in both sets.


Erich Karkoschka's enhanced Voyager picture


Uranus by Keck

We have now good resolution for both hemispheres. Can't wait to see a new map !!

Regards,
Marc.
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antipode
post Jan 8 2015, 04:25 AM
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Record-breaking Storm Activity on Uranus in 2014

http://arxiv.org/pdf/1501.01309

P
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Explorer1
post Jan 8 2015, 04:40 AM
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A key quote:

QUOTE
But even with such data, some questions may ultimately only be answered with a Uranus flyby or orbiter.


Yes please!
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TheAnt
post Jan 29 2015, 12:39 PM
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Could it be that Uranus have a more quiet period when one of the poles face the sun, and increased activity when both poles face the sun and we get a temperature difference from the equator and the poles with weather systems and these storms? The energy from the sun is indeed weak, but even so, this activity have indeed increased as the planet turned so it cannot be ruled out it is part of the reason for this increased activity.
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nprev
post Jan 29 2015, 06:13 PM
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I'd always assumed that was exactly the working hypothesis. The planet's atmosphere is drastically different in appearance than it was during the V2 flyby, and the obvious major external change has been the angle of solar illumination.

The equatorial regions would generally be expected to have more dynamic activity than the poles. Sheer speculation, but I wonder if the addition of direct solar heating to them either increases atmospheric mixing or facilitates some sort of photochemical process, either or both of which act to clear the haze.


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TheAnt
post Jan 31 2015, 01:59 AM
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QUOTE (nprev @ Jan 29 2015, 07:13 PM) *
I'd always assumed that was exactly the working hypothesis. The planet's atmosphere is drastically different in appearance than it was during the V2 flyby, and the obvious major external change has been the angle of solar illumination..............


Oh yes, I am certain that you're right about that.
I posted when the thought struck me, though it quite obvious so I am certain it must have been mentioned somewhere. smile.gif
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antipode
post Jun 5 2015, 10:23 AM
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Wow. Keck AO does it again.

http://www.sciencedirect.com/science/artic...019103515002390



Even better if you have a subscription.

Let's hope for a mission, even a multi-tasked flyby, before we all fall off the perch.

P

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rboerner
post Jun 5 2015, 08:03 PM
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QUOTE (antipode @ Jun 5 2015, 02:23 AM) *
Let's hope for a mission, even a multi-tasked flyby, before we all fall off the perch.


It doesn't look good for new flybys. The consensus seems to be that they're just not worth the money.

https://forum.nasaspaceflight.com/index.php?topic=33971.140

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Ian R
post Jun 6 2015, 03:02 AM
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