Celestia Forums

An interesting blog entry about extracting data about the un-illuminated hemispheres of the Uranian satellites from Voyager 2 imagery. Details are visible in the hemispheres lit by reflected light from the planet.

I saw this posting too. I was impressed by the results for Ariel. I think it would worthwhile to incorporate the reprocessed data into Celestia's texture map for this moon.

--Chris

Hmm. Why didn't anybody notice this before? Messing around with an image is one of the first things I do. If I find something I think is interesting, I take the image, and manipulate the heck out of it to learn more about it, usually by increasing brightness and contrast.

Furthermore, I'm not convinced that this is all authentic. But of course, I may be wrong. I'll do more research.

Here's the best image I can find of Ariel...

Note, no night-side features visible. And I'm sure that, back in 1986, if they were visible, they would have been exploited and examined.

And now these guys' image...


In addition to just looking too high quality, these "new" night side features become visible. Simply put, I'm not convinced. This is not to say I don't want them to be real... I do. I want to believe I'm actually seeing Ariel's night side... but at the moment, I simply don't believe it fully yet.

Hungry,

Your "best image" is in jpeg format, so it is not the original data: it already has lost all of the subtle detail. Any image manipulation has to start with an image in the original data format.

selden wrote:Your "best image" is in jpeg format, so it is not the original data: it already has lost all of the subtle detail.

In addition, just to make it a bit worse, JPEG compression introduces artifacts of its own... not good.

Hungry,

it's not only a matter of lossy formats (Selden, Andrew), but also largely of previous image manipulations that affect the image contrast. Making a raw image more contrasty will exactly push some dark pixels to black, such that the respective info is gone for ever.

So try and find tha RAW data in the respective mission storage location!

F.

Independent of seeing the night side or not,this half face image is better looking and have more details than the 1k or less texture of Uranian Moons.So,I thik it??s possible to improve textures of Arial,Miranda and others.Even planets like Mercury and moons like Titan have some textures in different resoutions.Of course,I can be wrong...

t00fri wrote:Hungry,

it's not only a matter of lossy formats (Selden, Andrew), but also largely of previous image manipulations that affect the image contrast. Making a raw image more contrasty will exactly push some dark pixels to black, such that the respective info is gone for ever.

So try and find tha RAW data in the respective mission storage location!

F.

t00fri, image contrast wasn't all I used. I used a combination of that and image brightness (increasing the brightness significantly before adding contrast). Nonetheless, I do realise that not using the original data could result in loss of information.

chris wrote:I think it would worthwhile to incorporate the reprocessed data into Celestia's texture map for this moon.

I seem to remember that some time ago you had plans to implement "planet/moon shine" into Celestia's rendering engine. I may have remembered this incorrectly (maybe it was someone's wish-list rather than any definite plans, and I can't locate the relevant posts), however IMO if you do have plans to implement such features at some point, then I think it would be wrong to incorporate brightening into the textures themselves. (Except perhaps as an interim measure)

CC

Hungry4info wrote:t00fri, image contrast wasn't all I used. I used a combination of that and image brightness (increasing the brightness significantly before adding contrast). Nonetheless, I do realise that not using the original data could result in loss of information.

Hungry,

I was NOT talking about what YOU used, but rather what someone used to do that brown color image above. It was clearly contrast enhanced. Raw images usually have a MUCH flatter contrast, precisely not to cut away subtle features before the final processing.

F.

Chuft-Captain wrote:

chris wrote:I think it would worthwhile to incorporate the reprocessed data into Celestia's texture map for this moon.

I seem to remember that some time ago you had plans to implement "planet/moon shine" into Celestia's rendering engine. I may have remembered this incorrectly (maybe it was someone's wish-list rather than any definite plans, and I can't locate the relevant posts), however IMO if you do have plans to implement such features at some point, then I think it would be wrong to incorporate brightening into the textures themselves. (Except perhaps as an interim measure)

Planetshine is one of the things that I want to add to Celestia. However, this has no impact on the usage of the reprocessed Uranus maps. There's no 'brightening' incorporated into the textures--the features visible because of planetshine would also have been visible in sunlight had the Sun been shining on them.

--Chris

Planet-shine would certainly be my number one feature request at the moment.

Hungry, the image you showed (the brown colored one) is not the raw data but was itself processed from the original raw data. Ted went back to the original raw data (which you can search for at http://pds-rings.seti.org/catalog/vgriss.html ) and processed that data. I've only played a bit with the Ariel data (more so than any of the other Uranian satellites to be honest) but I did recall features being visible in Uranus-shine, but not with the kind of detail Ted has been able to pull out.

volcanopele wrote:
Hungry, the image you showed (the brown colored one) is not the raw data but was itself processed from the original raw data. Ted went back to the original raw data (which you can search for at http://pds-rings.seti.org/catalog/vgriss.html ) and processed that data.
...

my saying, see above.

F.

volcanopele wrote:Planet-shine would certainly be my number one feature request at the moment.

Hungry, the image you showed (the brown colored one) is not the raw data but was itself processed from the original raw data. Ted went back to the original raw data (which you can search for at http://pds-rings.seti.org/catalog/vgriss.html ) and processed that data. I've only played a bit with the Ariel data (more so than any of the other Uranian satellites to be honest) but I did recall features being visible in Uranus-shine, but not with the kind of detail Ted has been able to pull out.

Thank-you very much for that link! Using the image from here http://pds-rings.seti.org/browse/VG_000 ... 684539.GIF, and using the image brightness and contrast, I'm able to make out two features on the night side, the two bright spots near the bottom of the image.

chris wrote:Planetshine is one of the things that I want to add to Celestia. However, this has no impact on the usage of the reprocessed Uranus maps. There's no 'brightening' incorporated into the textures--the features visible because of planetshine would also have been visible in sunlight had the Sun been shining on them.

Sorry, I was having a blonde moment.
Obviously Voyager 2 wasn't in the vicinity of the moon for long enough to capture all sides of the moon lit by the sun, so details of probably 1/2 the surface can only be seen in the planetshine illumination. (Probably would have helped if I'd read the blog first )

Chuft-Captain wrote:

chris wrote:Planetshine is one of the things that I want to add to Celestia. However, this has no impact on the usage of the reprocessed Uranus maps. There's no 'brightening' incorporated into the textures--the features visible because of planetshine would also have been visible in sunlight had the Sun been shining on them.

Sorry, I was having a blonde moment.
Obviously Voyager 2 wasn't in the vicinity of the moon for long enough to capture all sides of the moon lit by the sun, so details of probably 1/2 the surface can only be seen in the planetshine illumination. (Probably would have helped if I'd read the blog first )

The green-blue light from Uranus makes for some striking planetshine. Here's Miranda:



--Chris

Cool to see new features incorporated into Celestia as we speak

Steve Albers incorporated a piece of Uranus-shine in his map of Ariel already in 2006.

Somewhat related topic.

I really wish they would send a mission to Uranus. Currently, it's positioned in the right phase angle to where the moons actually receive sunlight across their entire surface (expect perhaps a tad bit of the north pole now). Global maps of the Uranian moons would be great. Those moons have a lot of interesting features that cry out for investigation.

If not this opportunity, maybe in 50 or so years when Uranus is back to the same angle?

Hungry4info wrote:Somewhat related topic.

I really wish they would send a mission to Uranus. Currently, it's positioned in the right phase angle to where the moons actually receive sunlight across their entire surface (expect perhaps a tad bit of the north pole now). Global maps of the Uranian moons would be great. Those moons have a lot of interesting features that cry out for investigation.

If not this opportunity, maybe in 50 or so years when Uranus is back to the same angle?

Current rocket technology cannot propel a spacecraft much beyond Jupiter. To get a probe all the way to Uranus, at least one gravity assist is required.

In any case, if we were to have a mission to Uranus, it's far too late to send it. Firstly, the journey would take about nine years, and secondly the mission would require about the same amount of time to plan it, build it and launch it.

So if we were to have a probe arriving at Uranus now, the mission should have been started in 1990 or so.

The next equinoctal photo opportunity for Uranus is in 2049. A mission arriving then may need to be started in 2031 or so.

I use Steve Alber's Ariel map that incorporates the planetshine. I followed Voyager 2 by in 1986 with SVN Celestia and could see the big white spot.

I also made a new lok texture to not cover that area.