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Neptunian System Imaging
antipode
post Jul 19 2018, 07:26 AM
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Amazing image, although I hope the EELTs will do better (and faster than the next ice giant mission).

Although orbiters are badly needed to both, I wonder if cheaper New Horizons-like flybys might not be more likely
as long as there is suitable geometry for a subsequent large (spherical) TNO flyby after? So many are binaries you'd
get quite a lot of bang for the buck.

p
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JRehling
post Jul 19 2018, 06:15 PM
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Here's a state of the art image of Ganymede using the 5m Hale Telescope.

http://www.unmannedspaceflight.com/index.p...st&p=233427

The ELT (named changed from the previous E-ELT) will have 8 times the aperture, and Neptune is roughly 8 times more distant than Jupiter, so that indicates the resolution that will be possible for the Neptunian system and similarly distant objects such as Pluto. Of course, the ELT will not be dedicated to Neptune observations. I think we can safely say, however, that global Neptunian weather patterns can be tracked by other multi-meter telescopes from the ground and so the return-on-investment of Neptune missions decreases accordingly.

For fine detail of the planet and satellites, of course, there's no substitute for being there.

I think one of the best value propositions for Uranus/Neptune missions would be a flyby that targeted one of the larger TNOs and used the ice giants for a gravity assist on the way there. Four such missions could capture >75% coverage of selected satellites (obviously, Triton being one) and then provide an encounter of, potentially, New Horizons type value at Makemake, Haumea, etc. with great synergy in designing and manufacturing four identical craft with New Horizons legacy tech.

I don't see how a Uranus or Neptune orbiter could possibly jump the queue over many potential ambitions to closer targets of very high interest, Enceladus and Titan to name just two.
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jccwrt
post Aug 26 2018, 06:29 PM
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A recreated view of the Neptune system as seen by Voyager 2 at approximately 1615 UT. I picked this time because Voyager made back-to-back observations of Neptune and Triton, so the appearance of these bodies closely approximates what a simultaneous view would have looked like.


Neptune and Triton - Voyager 2

I used a wide-angle OGV shot of Neptune and a narrow-angle GV observation of Triton. I recreated the view using a Neptune Viewer plot taken at the center of the Neptune observation, and then placed the reduced-size image of Triton in the appropriate positions. The slight difference in the direction that the crescent horns point is real - their position relative to the Sun was close enough that the phase angle was different from Voyager's point of view.

There is one improvement that I can think of. Neptune's remaining "major" moons should have been present in this scene as well, but I am not sure about their visibility to an observer at Voyager 2's location. Their small size and the position of the spacecraft suggest that they would only be a pixel or two across in the wide-angle camera and most of that surface would be in darkness. I am planning to look through some Neptune images taken a couple hours later where Galatea and Thalassa are present in the frame, which should help me determine if including them in this image would be appropriate.
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jccwrt
post Jan 17 2019, 02:07 AM
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Working with some of my eclipse calculations from a few years back - I wanted to see if there were any interesting color sets of shadow transits at moderate resolution. I did find a decent set involving Despina's shadow early on August 24 through the WAC. Neptune itself is an OGV natural color image, but I have composited in the moons from several separate images. All three moons visible within this image are brightened by about 10x. (Naiad and Thalassa should both be theoretically visible but were below the detection limits with this exposure setting.)

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MarcF
post Feb 21 2019, 02:21 PM
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Nice new article in Nature about the inner moons of Neptune
The latest discovered inner moon of Neptune has now a name : Hippocamp
https://www.skyandtelescope.com/astronomy-n...campaign=buffer

From the paper:
"Hippocamp orbits close to Proteus, the outermost and
largest of these moons, and the orbital semimajor axes of the two
moons differ by only ten per cent. Proteus has migrated outwards
because of tidal interactions with Neptune. Our results suggest that
Hippocamp is probably an ancient fragment of Proteus, providing
further support for the hypothesis that the inner Neptune system
has been shaped by numerous impacts."

Also, Naiad hadn't been seen since Voyager 2's flyby. Showlater's team did spot it — but in a spot diametrically opposite where it should have been, based on the presumed orbit. Thalassa (92 km) proved less challenging but was still displaced 19° from its predicted orbital longitude. The team also reports that no other moons larger than 24 km likely lie within 200,000 km of Neptune or larger than 20 km farther out.

The ring/inner moons system of Uranus was known to be a very dynamic system. The same seems to be true with Neptune ring/inner moons system.
Regards,
Marc.
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TrappistPlanets
post May 5 2021, 02:59 PM
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Was any parts of Neptuneshine on triton visible during the closest approach?
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JRehling
post May 5 2021, 03:39 PM
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The timing of the Voyager 2 encounter at Neptune was almost perfectly wrong for such opportunities. Triton's Neptune-facing hemisphere was in sunlight at the time of the encounter.
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TrappistPlanets
post May 5 2021, 05:22 PM
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QUOTE (JRehling @ May 5 2021, 04:39 PM) *
The timing of the Voyager 2 encounter at Neptune was almost perfectly wrong for such opportunities. Triton's Neptune-facing hemisphere was in sunlight at the time of the encounter.

so at what point in the encounter gives us the higher quality neptuneshine sense closes point it was in sunlight
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Phil Stooke
post May 5 2021, 05:29 PM
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If I am remembering this correctly, when Voyager 2 flew past Triton, Triton was the most distant known object in the solar system. Pluto was near perihelion and closer to the Sun, and the KBOs we know today had not been discovered yet. Triton was beyond Neptune and Nereid was closer to the Sun.

Phil


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NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain)
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john_s
post May 5 2021, 06:19 PM
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Actually there would have been some Neptune-lit terrain visible to Voyager during the close Triton flyby- the sunlit terminator extended to about 40 degrees north, but the Neptune-light terminator would have reached ~90 degrees north, and the intervening parts of the northern hemisphere were in direct view from Voyager 2 on approach (as Voyager was coming almost directly from the direction of Neptune). Lighting was poor, though- Neptune was a crescent as seen from Triton at the time, and of course even sunlight illumination was challenging for imaging with Voyager's vidicon at Neptune. I don't recall seeing any successful detection of Neptune shine on Triton in the Voyager data.

John
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TrappistPlanets
post May 5 2021, 10:18 PM
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QUOTE (john_s @ May 5 2021, 07:19 PM) *
Actually there would have been some Neptune-lit terrain visible to Voyager during the close Triton flyby- the sunlit terminator extended to about 40 degrees north, but the Neptune-light terminator would have reached ~90 degrees north, and the intervening parts of the northern hemisphere were in direct view from Voyager 2 on approach (as Voyager was coming almost directly from the direction of Neptune). Lighting was poor, though- Neptune was a crescent as seen from Triton at the time, and of course even sunlight illumination was challenging for imaging with Voyager's vidicon at Neptune. I don't recall seeing any successful detection of Neptune shine on Triton in the Voyager data.

John


Ted Stryk did got a huge amount of neptuneshine on Triton but it was on a low res departer image, and i like some higher quality neptuneshine even if its just a part of it and not all of it

https://cdn.discordapp.com/attachments/7275...t_of_triton.png

where is the pole, i tried reprojecting this (above (link) before but i think my attempt was wrong so where is the pole?
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TrappistPlanets
post May 5 2021, 11:54 PM
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QUOTE (TrappistPlanets @ May 5 2021, 10:18 PM) *
Ted Stryk did got a huge amount of neptuneshine on Triton but it was on a low res departer image, and i like some higher quality neptuneshine even if its just a part of it and not all of it

https://cdn.discordapp.com/attachments/7275...t_of_triton.png

where is the pole, i tried reprojecting this (above (link) before but i think my attempt was wrong so where is the pole?



here is my newest attempt (from today (credits to sckenk and ted)


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JRehling
post May 6 2021, 03:07 AM
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QUOTE (TrappistPlanets @ May 5 2021, 10:22 AM) *
so at what point in the encounter gives us the higher quality neptuneshine sense closes point it was in sunlight


In principle, there would have been some time after the encounter when Triton was in a "new" phase as seen from Neptune, but Voyager 2 would have been very far away at that time. Voyager 2 was moving very fast when it passed Neptune, entering and then leaving proximity in well under a day. Triton would have taken about three days to get back around to a "new" phase.
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TrappistPlanets
post May 6 2021, 01:55 PM
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QUOTE (JRehling @ May 6 2021, 03:07 AM) *
In principle, there would have been some time after the encounter when Triton was in a "new" phase as seen from Neptune, but Voyager 2 would have been very far away at that time. Voyager 2 was moving very fast when it passed Neptune, entering and then leaving proximity in well under a day. Triton would have taken about three days to get back around to a "new" phase.


did i reproject the neptuneshine correctly in the map above your post?


okay so what image of triton would give us the highest quality chunk of neptunshine of ted were to pull it out?
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ZLD
post Aug 1 2022, 07:17 PM
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New Hubble data products on the 2018-2020 Neptune spot evolution were just released.

https://archive.stsci.edu/hlsp/nds-2018

Looks like the current paper isn't open access (yet). Previous paper from the same group (open access): https://agupubs.onlinelibrary.wiley.com/doi...29/2019GL081961


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