Uranus System Imaging Options

[machi]

I finished my first good image of Uranus.
Planet is colorized from three filtered images (orange, green, blue).
Slightly brownish color of rings is entirely artificial.

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[Hungry4info]

That's pretty neat, ^.^, though the rings look a bit bright =o.

[machi]

Yes, rings look bright, because their brightness is enhanced.
Rings are in fact barely visible.
Original exposition times were 15.36 s for rings images (clear filter) and 0.72 (blue filter), 1.44 (green filter), 5.76 (orange filter) for Uranus images.
Despite of these exp. times, rings were still very dark (much darker than Uranus).

[machi]

Probably highest resolution image of Uranus with some details (~12 km/pix).
Color from green, violet and synthetised images.

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[antipode]

Hey thats very nice! Has this dataset been ignored because it was assumed nothing much could be squeezed out of it?

P

[machi]

Possibly. But I think, that lots of information is still hidden in these images. And for long time, these are best images of Uranus.

[tedstryk]

Great work! I have always focused on the moons, never the planet.

[antipode]

Ever since the original data was released, it always seemed to me that the response was 'big bland boring ball......oooh look at that pretty Miranda over there!' Now that the planet has gone through equinox and we have Hubble and Keck etc, we know better, but still the popular assumption is that the planet is just a big featureless fuzzy ball.

Given that you are right, and that we are likely to see Neptune close up (Argo?) before we see Uranus close up, I for one am very interested in what you find in this dataset. Maybe with a bit of suitable processing it will surprise us all!

P

[elakdawalla]

If you haven't seen it, you should check out Bjorn Jonsson's version of a Voyager Uranus image, posted with lots of his comments about processing. The key thing of interest in reply to antipode's post is that he found no features in the images that were significant enough to make it worthwhile to rotate the three frames in 3D space to align them before creating the color composite.

Also, regardless of whether Argo is selected, I think Neptune will be visited again before Uranus, because of Triton.

[Bjorn Jonsson]

If you haven't seen it, you should check out Bjorn Jonsson's version of a Voyager Uranus image, posted with lots of his comments about processing. The key thing of interest in reply to antipode's post is that he found no features in the images that were significant enough to make it worthwhile to rotate the three frames in 3D space to align them before creating the color composite.

This is different from my Jupiter, Saturn and Neptune processing where I usually rotate the images in 3D space. For Uranus I didn't see the need for that as the features are very low contrast in OR, even more low contrast in GR and not visible at all in BL.

Uranus is no less interesting than Neptune in my opinion. Being visually bland doesn't make a planet uninteresting, it just makes it more difficult to explore. Comparing Uranus and the other the other big 3 there are interesting differences, for example Jupiter, Saturn and Neptune radiate significantly more energy into space than they receive from the sun while Uranus doesn't - it radiates hardly any excess heat. And with the exception of Triton, Uranus' satellite system is actually more interesting than Neptune's. Comparison with the Cassini results at Saturn would be interesting.

I have sometimes been a bit frustrated that Voyager 2 couldn't be launched a bit later (or technology developed faster) because then it could have carried a CCD camera sensitive to near-IR. The amount of visible details increases greatly with wavelength (comparing OR and BL there is a big difference) so I suspect Uranus would look highly interesting to a Cassini (or even Galileo) style imaging system in the near-IR.

Probably highest resolution image of Uranus with some details (~12 km/pix).
Color from green, violet and synthetised images.

This is extremly interesting, possibly the most interesting Voyager 2 image I have ever seen of Uranus. Now I wonder if there are any images of comparable resolution extending further 'down' and thus showing the bright feature better...

[machi]

I have seen Bjorn Jonnsson's image of Uranus and in fact, I use this image as color ethalon

Uranus or Neptune? Don't forget on Uranus Orbiter! Team from JPL (also APL?) has mission scenario within New Frontiers budget. They planning solar! powered orbiter.

Now I wonder if there are any images of comparable resolution extending further 'down' and thus showing the bright feature better...

Probably no one in PDS online archive.

[Bjorn Jonsson]

It's actually quite interesting to attempt to squeeze out some details from these images but having worked mainly on Cassini images recently the image quality really sucks. Here is a quick and dirty version of image C2682833.IMQ:



Some details are visible as well as various processing artifacts and noise. In particular, the concentric ellipses are processing artifacts. This is an orange filter image from directory URANUS\C2682XXX on Voyager volume 2 (the most interesting images are probably in this directory and the directories immediately preceding and following it). The orange filtered images seem to contain the greatest amount of details but some details are also visible in the green images.

Someone should probably be able to come up with an improved version of this one.

[Hungry4info]

They planning solar! powered orbiter.

Lol...

How big of an array?

[stevesliva]

In particular, the concentric ellipses are processing artifacts.

Pity. I was just convincing myself that the second ring was hexagonal.

[Stefan]

Someone should probably be able to come up with an improved version of this one.

Here's my take on that image (WAC green filter image 26828.33):



I think the only real feature is that bunch of clouds at the bottom.

[machi]

I was wrong! Is one image with slightly higher resolution, but photographed by Voyager 2 before image, which I posted above. But in this image is surface actually closer, so resolution is 11.5 km/pix compared to 11.7 km/pix in picture above.

And something to Uranus orbiter:
http://www.lpi.usra.edu/decadal/opag/UranusOrbiter_v7.pdf
http://www.lpi.usra.edu/decadal/opag/Uranu..._v7_Authors.pdf
http://spacepolicyonline.com/pages/images/...20Sat%20Sci.pdf

Online presentation (with audio) is somewhere too, but I don't know where.

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[machi]

Best image of Uranus south pole. Circular feature is real (some details not). Nearly horizontal lines are artifacts from flatfielding.

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[stevesliva]

The slightly lighter core inside the darker second ring could be faceted like the Saturn hexagon. But any sort of blips at single 60-degree intervals from each other is enough to make part of a blurry circle look like part of a hexagon.

Pretty cool to see structure there, though.

[machi]

Effectively highest resolution view from any of Voyagers. Two shots after well known Miranda mosaic images. NAC frames over one WAC frame. Color is artificial, but very close to real. It's based on the HST photometry. Resolution is 280 m/pix.

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[Decepticon]

Wow! Love your work.

[machi]

Thanks Decepticon!

And new image from Uranus system - moon Ariel. Resolution of this stereopair is around 1.55 km/pix.

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[machi]

Moon Ariel resampled at 1 km/pix (real resolution ~ 1.2 km/pix).

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[Stefan]

Stunning!

[ugordan]

Nice work, keep it coming!

[antipode]

WOW! That's the best look at that moon I've ever seen!

Actually its so good I'm looking at that dramatic resurfacing in a new light. There's a real paucity of medium to large craters in that image?

P

[machi]

Stefan and Ugordan: Thanks!

Antipode:
Actually yes, surface of Ariel is relatively young. I don't know about any large crater on that moon. Even medium craters are scarce.
Moreover some parts looks like surface of Enceladus. In terms of geologic activity, Ariel is perhaps between Enceladus and Dione.

[tedstryk]

Great work! That is the mosaic I based my first LPSC conference on http://www.planetary.org/blog/article/00001362/

[DrShank]

Great work! That is the mosaic I based my first LPSC conference on http://www.planetary.org/blog/article/00001362/

always nice to see a continued interest in the verdant orb.

dont forget these nice bits, including topography:
http://stereomoons.blogspot.com/2009/08/more-ariel.html

[machi]

Great work! That is the mosaic I based my first LPSC conference on http://www.planetary.org/blog/article/00001362/

Yes, I know about this, more of your images are in this topic http://www.unmannedspaceflight.com/index.php?showtopic=3932 .
My favourite is your "combo" image, but now, I don't know exact adress.

dont forget these nice bits, including topography:
http://stereomoons.blogspot.com/2009/08/more-ariel.html

This is something new for me. I know your work on galilean satellites, saturnian satellites, Miranda and Triton, but I missed Ariel. I especially love black and white topography maps!

"New" images of Umbriel. Image data were resampled to 3 km/pix and 5 km/pix (clear-clear-violet-green sequence) and combined together. Real resolution is 5.16 km/pix and 9.67 km/pix (multicolor sequence).

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[machi]

Three images of Titania. All resampled from original resolution 6.7 km/pix, 4.6 km/pix and 3.4 km/pix.

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[tedstryk]

Very nice work.

[antipode]

Ditto.

Im enjoying this thread, and enjoying the better press Uranus is finally getting lately (jokes aside, I think the active equinox atmosphere has helped silence the 'totally bland' press the planet has had since 1986).

Back to the moons. I wonder (Wunda? ) how many decades it will be before we get a better peek at Umbriel's strange Wunda? Looks very Iapetaen.

P

[ugordan]

Three images of Titania.

Is the color shift to red/pink near the terminator real or an artifact?

[machi]

Ted: Thanks!

Antipode:
I'm always enjoying work with Uranus moons, I hope this is another small piece of work which leads to support new mission to these strange lands.
"Wunda? Looks very Iapetaen" I think so too .

Ugordan:
All three images shares same color data from medium resolution image.
I used different processing technique to highest resolution image which leads to slightly bigger color differences.
So I think color shift is real, but slightly more enhanced than on another two images (and terminator regio isn't so good visible on these two images).

[tedstryk]

I have also noticed the color shift.

[ugordan]

It looks like a calibration artifact at first, but then if you look closer it looks like an albedo feature as it extends clockwise all the way to the sunlit limb at 5 o'clock. I think that's the most color variation I've seen on Uranus' moons.

[Stu]

You see? THIS is why I love UMSF so much... You Image Mages delve into the misty archives, drop the old, forgotten images dumped there into your cauldrons, give a good stir and whumpf! out come amazing new views of these distant worlds...

Many thanks for sharing these beautiful pics, guys.

[machi]

Ugordan, Tedstryk:
In case of color shift near the terminator, I think that's combination of imperfections of calibration (which are more evident at low brightness level) and real surface color. I looked at maps and redder hemisphere is around 90° longitude. I think it's the leading hemisphere.

Stu:
Image Mage, nice phrase
"forgotten images dumped there into your cauldrons"
My secret ingredient is bat's ear but keep it under your hat

Last in set - Oberon.
Resampled at 3 km/pix. Real resolution 7 km/pix.

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[ugordan]

Here's a color version of Titania using calibrated data from the PDS rings node:


Left is gamma-correct, right is contrast enhanced.
While that calibrated data set is known to have calibration issues and is not the greatest quality Voyager ISS data set in the world, it appears to be missing the color shift around the terminator.

Taking a quick look in green+violet (as well as using clear as an effectively 460 nm filter) color of all the moons, Miranda, Ariel and Umbriel appear to be effectively grey (Umbriel the most), while Oberon and Titania have that slight brownish tint to them.

[sariondil]

Machi´s version of the Oberon data set can be used to add a tiny bit of coverage along the terminator of Steve Albers´ map. I assume the color processing is different and just roughly adjusted the brightness.
While I´m at it, here´s a quick reprojection of the Titania nightside coverage dicovered by Ted Stryk onto Steve´s map (looks slightly mismatched, but dayside features line up in this position).

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[machi]

Anaglyph of Titania. It's based on synthetic frame between last two high resolution Voyager images of Titania.
Edges were removed.

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[algorimancer]

Anaglyph of Titania.

The fractures certainly stand out. A bit more topographic height than I would have expected. Neat.

[machi]

Cross-eye stereo image of Titania. Synthetic image is more precise than that one in previous anaglyph.
Resampled to ~2 km/pix. Edges were cropped from synthetic image.

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[nprev]

Daniel, you're a wizard. These are AMAZING.

[Bjorn Jonsson]

Agreed, this is amazing. Interestingly the anaglyph reveals that the surface is a bit depressed farther away from the big fracture than can be easily seen in the original imagery.

I want a Uranus orbiter! ;-)

[nprev]

I noticed that the (bear with me on the terminology here because this is Uranus & everything's tilted 98 deg) 'north polar' area seems depressed as well 'above' the large crater in the crosseyed pair.

Interesting little world among many there, well worth further investigation. Sure hope I live that long.

[machi]

Thanks!

I see many topographic details, but one must be careful about interpretation. For example some "details" can be simply artifacts from reseau marks.
But I made simple comparison with Titania topography obtained by photoclinometry from article
Large impact features on middle-sized icy satellites from Moore, Schenk, Bruesch, Asphaug and McKinnon (Icarus 171, 421-443)
and it looks very similar to their DEM of Gertrude regio.

This is cross-eye "stereo quaternion" made by same method. First pair is in principle same as my first cross-eye of Titania,
others are new for a little different perspective.
Two outer images are "original" (processed) images from Voyager, others are synthetic.
Edges are distorted, but I preserve them now for completeness (in cross-eye images, their aren't so disturbing).

EDIT: Anaglyph version is here.

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[ilbasso]

Wow! The anaglyph version looks almost like a hologram. The images appear to rotate slightly when you move your head from side to side. Beautiful work!

[Paolo]

some new, cool infrared images of Uranus and Neptune
http://www.space.com/13086-photos-neptune-...red-images.html

[stevesliva]

One thing that got mentioned on twitter but not there was the obvious eccentricity of Uranus's rings. Pretty neat.

[JohnVV]

For anyone interested .I put together an artistic extrapolation based on the Keck and Hubble images
http://celestiamotherlode.net/catalog/show...p?addon_id=1575

[MarcF]

I just found the following information:
Professional observers reported a very bright cloud on Uranus, using the Gemini telescope. They need amateur confirmation:

http://www.universetoday.com/90393/observi...ranus-reported/

The discovery was made over a month ago and it's strange that there is almost no mention to it in media (and even on the web) !
Best regards,
Marc.

[MarcF]

Dear all,

I just bought the book "Uranus" edited by Bergstrahl, Miner and Matthews. With over 1000 pages, it is still "the bible" of the Uranian system. There are many data, pictures, mosaics and schemes not found anywhere else. Looking at the maps of the moons, I realized that there were still many important features without a name (especially on Miranda).
Just few examples:
the 340° chasma,
the South Pole Tangent chasma,
the Arden Concentric chasmata.
There are also many other interesting linear features as well as craters and basins deserving a name (not only on Miranda).
Most of the names were given in 1988. Three others were added in 1997.
I'm wondering about the rules to decide to name features. Will we have to wait the next mission to the Uranian system (20 years from now at best) to get some new ones ?
Best regards,
Marc.

[Phil Stooke]

Check out this website:

http://planetarynames.wr.usgs.gov/

You will see lists and maps of names throughout the solar system (only lists for the Uranian satellites so far), but also a lot of background information including naming themes, and a form for suggesting names.

You can suggest names, as anyone can, but typically they are not accepted unless there is a compelling reason such as a new mission (look for new names soon in the Gale crater area on Mars), a new scientific study (recent names on Mars include small dark-rayed craters, for instance, based on a recent study) or a forthcoming geological map.

I have made suggestions in the past, but never had any adopted!

Phil

[MarcF]

Thanks Phil,
Maybe I will try to suggest some ! Who knows ?
Marc.

[jasedm]

Will we have to wait the next mission to the Uranian system (20 years from now at best)

I'll be in my 60's....

[scalbers]

Greetings. Here are the present versions of my Uranian satellite maps with feature labels, starting with Miranda and Ariel:





Pixie Chasma looks a bit ambiguous to me, is it the feature north or south of the label?

(Updated March 3, 2012)

Steve

[scalbers]

And here's Umbriel assuming a 265 degree center longitude in Phil's map.



Titania below:



(Updated March 3, 2012)

[scalbers]

Finally - here's Oberon:



(Updated March 3, 2012)

[antipode]

Little surprised that no one has commented on this:

http://www.astrobio.net/pressrelease/4694/...psed-from-earth

Very cool. Been waiting for something like this for a long time.
If the phenomena are transient presumably people will now be able to monitor more assiduously.

Neptune next?
P

Edit: I guess this could have gone in telescopic observations. But what the heck, its not like there are fleets of spacecraft heading out that way...

[Phil Stooke]

I only just noticed Steve's question about Pixie Chasma above - the Chasma is right underneath the label.

Phil

[morganism]

Keck observations bring weather of Uranus into sharp focus

http://phys.org/news/2012-10-keck-weather-...harp-focus.html

[Ken90000]

Wow. The resolution is incredible. It will be interesting to see the evolution of those features near the pole over the next few years. Cannot wait to see what they do with Neptune.

[Phil Stooke]

Yes, they really are amazing. I would like to see Ceres imaged like that now!

Phil

[MarcF]

Wow, I cannot believe it ! Uranus as we never have seen it ! Looks a lot like Jupiter !

[JohnVV]

time to remap the above keck images and incorporate it into the Uranus map
old map - Artists concept


getting any good data out of the voyager images is not easy

[Bjorn Jonsson]

WOW!!! To me these may be the planetary images of the year 2012. I feel like I'm looking at a completely new planet. Of the two ice giants it has always been Uranus that seemed to be more different visually from Jupiter/Saturn but now it suddenly seems the opposite may be true. It looks remarkably similar to Saturn. It's not only the north polar region that looks similar to Saturn's south polar region - Saturn has scalloped bands as well.

I never stop wondering what Voyager 2 would have seen had it been able to carry a Galileo/Cassini style imaging system, i.e. a CCD camera with near infrared filters. Uranus is so much more active-looking at infrared wavelength than it is in visible light. This is a great example of the fact that planets that look visually bland are not uninteresting. They are just more difficult to study.

I have said it before and I'm going to repeat it ;-) : I want a Uranus orbiter or flyby mission in my lifetime.

[tasp]

I want a Uranus orbiter or flyby mission in my lifetime.

Bjorn


Don't recall if you were here 'back in the day' but we learned a 'Galileo' style orbital tour of Uranus with many close satellite flybys is possible since Uranus and it's entourage are scaled, so to speak, down model of Jupiter system.

It could be a very exciting mission.

[machi]

Amazing images and amazing technical story. I remember from late 80's, that even in the biggest telescopes, we could see Uranus like small bluish disc nearly without any discernible details.
Then HST came and first nice images from outer Solar system. And now we have telescopes with adaptive optics, which can produce such sharp images.
And before us is new ELT era. So as everyone here, I want Uranus orbiter, but even without it, we can expect even better images in "near" future (~20's).

[Phil Stooke]

Just fooling around with images - and a big thankyou to the creators of these original images, obviously.

I have merged one of the spectacular new images with a true (-er) colour image released a while ago (it's the one with the dark spot - if you look closely you will see it faintly shining through, and there's a new dark spot in the new image as well, at a different latitude). Purpose - just to show the new details in a manner a bit closer to the expected colours of Uranus. Disclaimer - the colours of the cloud belts change over time and the two images will not really match properly. This is just for illustration purposes.

Phil

[elakdawalla]

Tonight was the poster session where Larry Sromovsky was showing these images and I just about fell over when I saw them. Sromovsky was downplaying it, saying it was "easy" when you had adaptive optics on a 10-meter telescope with great seeing and high signal-to-noise. Easy for him to say Leigh Fletcher was standing next to me and saying "these are the greatest images of Uranus in the history of mankind. And womankind."

[belleraphon1]

Incredible.... can hardly believe these are from ground based telescopes.

What beautiful mysterious worlds these ice-giants are!

Craig

[MarcF]

Finally, "real" Uranus looks quite like the expectations previous to the Voyager flyby !

[antipode]

Impressive post-equinox atmospheric action on the formerly 'boring' Uranus from Keck...

http://www.keckobservatory.org/recent/entr...ather_on_uranus

P

[Bjorn Jonsson]

Shortly after finishing the flyby anniversary mosaic of Neptune I started thinking about Uranus, got an interesting idea, started processing the Voyager 2 Uranus images and came up with this (two versions of the same image):



I think these may be the most detailed Voyager 2 global images of Uranus I have ever seen (but they are far inferior to recent groundbased images).

The processing idea came from the description of the processing of these images of Uranus:

http://www.planetary.org/blogs/emily-lakda...eck-photos.html

In short, I used 6 orange and 6 green filtered images that I reprojected to simple cylindrical projection, removing (or at least greatly reducing) the effects of global illumination on the fly. This was sufficient to correct for Uranus' rotation but since the images were obtained over a period of ~5 hours this was not sufficient - it's necessary to correct for Uranus' fast east/west zonal winds as well. To do this I found a profile (and I think it's a very recent and up to date one) showing Uranus' zonal wind speed as a function of latitude. I used this to correct the individual cylindrical maps by shifting each image row in the east-west direction. I then stacked the 12 maps, rendered an image and then greatly increased the contrast and visibility of various features. In the left image I first enhanced the contrast and then sharpened the image with an unsharp mask. In the right one I first enhanced the contrast, then suppressed large scale brightness variations with a high pass filter and then further increased the contrast.

The source images were obtained on January 17, 1986 between 14:19:10 and 19:35:10. At this time Voyager 2 was ~9 million km from Uranus.

This is experimental work in progress and it is probably possible to get better results. A day earlier, a longer sequence of images was obtained but it took a longer time; I strongly suspect that there is a limit to how long the time can be if you want good stacking results but I don't know what this limit is. One interesting processing artifact that may occur if the zonal wind profile I'm using is inaccurate is that bright or dark features get too elongated in the east/west direction but I don't think this is a significant issue here. Interestingly, even if this happen the feature's longitudinal position can be accurately estimated as the average of the west and east edges of the feature, as pointed out in a very interesting article by Sromovsky et al. in Icarus 203 (1): 265–286 (2009). EDIT: It's actually in Fry et al., Astronomical Journal vol. 143, no. 6, June 2012 where this is pointed out (the Sromovsky et al. article is very interesting too though).

There is considerable noise in the above images but it should be fairly obvious which features are real and which ones are noise and/or image processing artifacts. All of the obvious bright spots are definitely real and all of the narrow bright/dark east-west cloud belts (there are several of these) should be real as well. The dark, "partial cloud belts" near the bright spots are real as well. Another faint "partial belt" to the right of the dark polar cap may be real but I'm not sure. Some of these features are completely new to me.

With the benefit of hindsight, it is apparent that the best way for Voyager 2 to image Uranus might have been to obtain a few big sequences of orange-only images (orange images show the biggest amount of detail) in as short a time interval as possible, maybe using the tape recorder to speed things up due to the low bit rate possible from Uranus. This would have made the stacking results better. But of course there was absolutely no way to know this back in 1986.

I think the images above might hint at what additional details Voyager 2 could have seen had it been able to carry a Galileo/Cassini-style imaging system with near infrared filters. And they may hint at what a future spacecraft might see if it arrives when the illumination geometry is comparable to what it was in 1986.

Uranus' is *not* an uninteresting planet, it's simply more difficult to observe than the other giant planets due to low contrast and hazes. In my opinion it's at least as interesting as e.g. Neptune - and significantly different from it.

[scalbers]

Nice view Bjorn - with a polar pentagon (or maybe hexagon).

[Bjorn Jonsson]

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.

[Bjorn Jonsson]

Here are two versions of an image from a stack of 8 violet filtered images:



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.

[MarcF]

Wow really nice Bjorn.
The latest Keck Observatory pictures of Uranus (August 2014) show massive storms:



Link to Keck Observatory

[Bjorn Jonsson]

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 :

[Stefan]

Voyager image processing magic by Erich Karkoschka:

http://uanews.org/story/clues-revealed-abo...erior-of-uranus

[MarcF]

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.

[antipode]

Record-breaking Storm Activity on Uranus in 2014

http://arxiv.org/pdf/1501.01309

P

[Explorer1]

A key quote:

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

Yes please!

[TheAnt]

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.

[nprev]

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.

[TheAnt]

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.

[antipode]

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

[rboerner]

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

[Ian R]

[Ian R]

Look at the equatorial band of scalloped clouds!

[antipode]

More astonishing AO imaging from Keck II and Gemini North. This blows my mind.





http://arxiv.org/pdf/1512.05009.pdf


Imagine what the ELT class scopes might offer!

Where's that Uranus orbiter!

[MarcF]

Voyager Mission Celebrates 30 Years Since Uranus:

http://www.jpl.nasa.gov/news/news.php?feature=4827

And nobody knows how long we still have to wait until next mission to this amazing world !

http://photojournal.jpl.nasa.gov/jpeg/PIA01391.jpg

Reason for edit: Please don't embed huge inline images, embed and link from a thumbnail. Thanks. -mod

[Bjorn Jonsson]

Today is the Voyager 2 Uranus 30 year flyby anniversary. Below are my recently reprocessed versions of the highest resolution Voyager 2 images of Titania and Oberon. They are from an unfinished image processing project I'm working on (Miranda, Ariel and Umbriel are unfinished and I might add color versions of Titania and Oberon).

First is Titania. The upper image is rendered from a sharpened stack of three polar maps. One additional image is available but it is too blurred to be useful for stacking. The original images were obtained on January 24, 1986 around 09:11 at a range of ~500,000 km.

The second one is from a stack of two maps. The original images were obtained on January 24, 1986 around 14:17 at a range of ~370,000 km.





The upper image is probably the sharpest version I have seen of these images. The lower one is comparable to Ted's version - interestingly parts of my version look slightly sharper than Ted's image whereas other parts look slightly sharper in Ted's version. I made no attempt to show Uranusshine on the nightside; Ted has done this at least as well as I could do.

And here's Oberon. This is from a sharpened stack of two polar maps. I could have used two additional images but they are fuzzy and would probably have degraded the final result. The original images were obtained at a range of ~665,000 km on January 24, 1986 around 08:50.



All of these images are enlarged relative to the original images. North is to the right (and slightly down) in all of the images. These images are not exactly detailed and really show the need for a new visit to the Uranus system. In a sense these bodies represent a 'transition' from Saturn's icy satellites to bodies like Pluto and Charon, all of which after the successful New Horizons flyby are far better explored than Uranus' satellites.

[nprev]

..."not exactly detailed", but stunning nonetheless. Beautiful work.

[JRehling]

A world that these images remind me of, visually, is Mercury. Obviously, the compositions are radically different, but they share a quality one doesn't see (often) in images of, say, the Moon, Callisto, or Rhea, which is that craters seem to excavate both dark and light material, depending in some way that may pertain to lateral variations in composition. And that indicates something rather interesting about primordial formation processes. So, it's interesting to see that on both Mercury, which is by far the solar system's most massive body without a multi-gigayear history of volatile and volcanic reworking of the surface, and these much smaller bodies with completely different composition.

[Bjorn Jonsson]

Interesting comparison to Mercury. The albedo variations of the surface material are interesting, especially on Oberon where both dark and light material seems to have been excavated in several craters. The resolution is frustratingly low though and makes it difficult to tell exactly what is happening (I wonder if the Voyager 2 imaging sequence would have been designed with image stacking/superresolution in mind had those image processing techniques been common back in 1986).

On Titania dark stuff in craters is far more rare than on Oberon. However, Titania's chasm reminds me of Ariel, Charon and Tethys. Of course detailed comparisons are diffcult since Charon and Tethys have been vastly better imaged than Titania. Ariel has also been compared to Charon but even though Ariel is considerably better imaged than Titania the imaging coverage there is far worse than at Charon. We really need to revisit Uranus!

[tedstryk]

Sorry, I'm just finding this now. Excellent work, Bjorn. I think part of the differences between these reflect the fact that I did a little more to suppress noise, although this possibly obliterated marginal detail (but I thought it looked better). Here are my versions of these images.





The Oberon image is a complete reworking from scratch. Unlike Bjorn, I used all four images (though desmearing was required), and the two lower quality images are weighted as only a combined 20% of the final product.

[Astroboy]

A gif of the 1/23/1986 Titania phase angle coverage using violet and green frames for my fellow UMSFites. The green channel is synthetic.



Non-rotated version:

[Astroboy]

Not as clean looking as the first image in this thread, but here's my own quick, dirty, kinda bad take on a color Uranus with one ring. The color is OGB and the ring was exposed by stacking the OGB frames along with most of the other images from the same filter/exposure cycle, none of which were exposed for rings/faint objects (besides the atmosphere of course, which was obviously very faint out there). Since these cycles repeated as part of a movie sequence, one could technically create color ringed Uranus movies using real, simultaneously taken data.



The ring can actually be faintly seen in some normally exposed, uncombined images.