Synchronizing Neptune's Great Dark Spot

[granthutchison]

Anyone know of a source of precise times for the various Voyager images of Neptune?
It occurs to me that from such images it would be easy enough to work out an approximate RotationOffset to give realistic views of Neptune in Celestia for the duration of the Voyager encounter. (The RotationPeriod for the GDS is known, and a little different from the System III rotation period for Neptune's magnetic field.)

Grant

[Kendrix]

Useless ! That darkspot is no more present on Neptune...

Others have been seen since 1989...

It seems that "spots" on Neptune don't last for as much time as Jupiter ones !

[granthutchison]

Useless ! That darkspot is no more present on Neptune...

Useless to you, maybe ...
I do know the GDS was short-lived: that's why I was said that I wanted to reproduce the correct appearance for the duration of the Voyager encounter only. If we have a Neptune texture with the 1989 spot on it, we might as well have it orientated correctly in 1989, since there is no chance of it being "correct" at any other time!
Several Celestia users have been interested in reproducing the Voyager encounter with Neptune, and we've optimized the satellite positions for that date, so we should get the GDS right, too, if we can.

Grant

[t00fri]

Useless ! That darkspot is no more present on Neptune...

Useless to you, maybe ...
I do know the GDS was short-lived: that's why I was said that I wanted to reproduce the correct appearance for the duration of the Voyager encounter only. If we have a Neptune texture with the 1989 spot on it, we might as well have it orientated correctly in 1989, since there is no chance of it being "correct" at any other time!
Several Celestia users have been interested in reproducing the Voyager encounter with Neptune, and we've optimized the satellite positions for that date, so we should get the GDS right, too, if we can.

Grant

We might eventually want to assign a "life time" to reasonably short-lived yet very prominent surface markings (red, dark and other spots, for example).
This would be in analogy to the life time for space mission projects that is already incorporated.

Can't be a big deal to do.

Then alternative "cloud" textures could be loaded, depending on the simulation date...

Bye Fridger

[jim]

Hi Grant,

Maybe this link helps ?

http://nssdc.gsfc.nasa.gov/imgcat/html/ ... page1.html

Bye Jens

[granthutchison]

Hi Jens:

Maybe this link helps ?

Thanks for your trouble, but this thread is more than a year old, mysteriously dragged back from obscurity.
I'm sure I subsequently posted a Neptune definition with the GDS correctly positioned for Voyager 2 (and I would have guessed that I did here, in this thread), but I'm afraid I now can't find the damn thing. Anyway, it excited no interest at the time, I do recall.
But here it is again (I found the numbers in my Celestia 1.2.5 installation ):

Code: Select all

   RotationPeriod         18.3  # Great Dark Spot during Voyager II encounter
   # RotationPeriod       16.11 # System III (magnetic field)
   Obliquity             28.03
   EquatorAscendingNode  49.235
   RotationOffset       320     # visually position GDS for Voyager II encounter
   # RotationOffset     228.65  # correct System III prime meridian

Grant

[Kolano]

Digging up a year old thread here, sorry.

Now that there are /w and /wo dark spot versions of Neptune on the Motherlode...
http://www.celestiamotherlode.net/catalog/neptune.php

Can someone suggest appropriate begin/end times so that the Dark spot only appears during the Voyager 2 flyby, with some reasonable assumptions at lifetime pre/post that period?