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Uranus and/or Neptune Exploration
Jackbauer
post Jun 13 2017, 07:41 PM
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ICE GIANTS PRE-DECADAL STUDY FINAL REPORT
(NASA)

https://twitter.com/jjfplanet/status/874366189622796288
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antipode
post Jun 13 2017, 10:43 PM
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Golly, now lets see what comes of it.
I'll be in my rocking chair if and when these things deliver but my god they are needed.

P
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stevesliva
post Jun 16 2017, 08:53 PM
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To ensure that the most productive mission is flown, we recommend the following:
• An orbiter with probe be flown to one of the ice giants
• The orbiter carry a payload between 90 and 150 kg
• The probe carry at minimum a mass spectrometer and atmospheric pressure, temperature,
and density sensors
• The development of eMMRTGs and HEEET be completed as planned
• Two-planet, two-spacecraft mission options be explored further

Launch would be 2030, arrival 2043 for Neptune
Launch would be 2031, arrival 2043 for Uranus

All of the above: Orbiter and Probe for both projected to cost $3.671B ... $125M per year for the next 30 years.
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Decepticon
post Jun 16 2017, 09:37 PM
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I get sad seeing those dates. I don't know if I'll be on earth anymore to observe those missions.

Uranus moons have so much to show us still.
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Explorer1
post Jun 16 2017, 11:59 PM
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A launch on the SLS to avoid a bunch of inner solar system gravity assists would speed the trip up.
Trouble is, getting to the ice giants faster means using more delta-v to slow down, as the paper notes. There must be some good balance of the two pressures. We can always hope for a propulsion breakthrough...
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craigmcg
post Jun 17 2017, 12:43 PM
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This week's Planetary Radio also mentioned briefly that there was an option to fly Cassini to Uranus, although she characterized it as a "1%" option.

http://www.planetary.org/multimedia/planet...er-cassini.html
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Explorer1
post Jun 17 2017, 02:29 PM
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There were a number of such concepts for Cassini EOM. More details here (http://www.lpi.usra.edu/opag/march_08_meeting/presentations/spilker.pdf)
20 (!) years to get to Uranus after Saturn escape! Easier to just go from Earth with a whole new mission.
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tedstryk
post Jun 21 2017, 09:41 PM
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QUOTE (stevesliva @ Jun 16 2017, 08:53 PM) *
Launch would be 2030, arrival 2043 for Neptune
Launch would be 2031, arrival 2043 for Uranus


Brings new meaning to, "When I'm 64" (or 63 if it's early in the year).


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Explorer1
post Jun 22 2017, 10:02 PM
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On the bright side, if a orbiter is at Neptune in April 2046 with a good imager, it will have quite the show: http://xplanet.sourceforge.net/Gallery/20460429_jupiter/
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James S.
post Jun 22 2017, 10:15 PM
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QUOTE (Explorer1 @ Jun 22 2017, 05:02 PM) *
On the bright side, if a orbiter is at Neptune in April 2046 with a good imager, it will have quite the show: http://xplanet.sourceforge.net/Gallery/20460429_jupiter/

That would be awesome. I'll be 79 if I'm still alive.


--------------------
Axes Grind and Maces Clash!
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Explorer1
post Sep 29 2017, 04:53 PM
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Looking at the maps of the solid bodies in the outer solar system, I figured this to be the best place to ask (as we all want better maps!):
Given the high axial tilts of the Uranian moons (and Triton), when combined with their lengthy seasons, how would an orbiter conduct mapping the geography/geology of the unlit hemispheres? As we saw at Pluto, one ends up with a giant fraction of the map remaining completely unknown; even a future Pluto orbiter would have to wait many decades for sunlight to reach the southern hemisphere.
What sort of instrumentation could deal with this? There is only so much reflected light from the planet one can use like Cassini did (and even then only for the planet-facing hemisphere). Is RADAR like Cassini's practical at all? Something like MOLA on Mars Global Surveyor? Star occultations behind the limb during a flyby could get outlines of particular dramatic topography, like Miranda's canyons? Maybe a really big flashlight? Just brainstorming, and I'm curious if anyone else has thought about it.
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tasp
post Sep 29 2017, 10:57 PM
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Here's a combined view of Enceladus in light and radar (radar scan is in the arc shaped area). Radar appears to have worked quite well. (Haven't posted a picture here in years, hope I do it right)

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ngunn
post Sep 29 2017, 11:23 PM
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That's a really interesting enquiry. I would first like to add a complicating factor which is that the superficial appearance of these bodies may change significantly on a seasonal timescale. For example the parts of Pluto and Triton that we saw by day might look quite different during a long polar night as a result of 'repainting' by mobile volatile materials. Even a perfect night-time flashlight might show a different map. That said, the topography would not change and that could be reliably mapped by radar. How much do we learn from visible light images compared with a really good topographic survey? I don't know but would be interested in expert opinions.
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JRehling
post Sep 30 2017, 05:21 AM
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A few thoughts here…

A mission that arrived just before equinox would soon see the entire surfaces of the whole system, so that would be one approach (two flyby craft would be another), but doesn't address the question of seasons.

These worlds have a lot less gravity than Triton or Pluto and they're much closer to the Sun, so I'd be skeptical about seasonal dynamics on a grand scale.

It's always possible that a seasonal change would consist of a very thin layer that has profound implications for albedo but would be invisible on the scale of geomorphology. Earth and Mars both show such things. Radar may see right through a thin layer, but depending upon its dielectric properties, may see it as a major change in radar albedo.

I don't think radar is likely to make the cut for a Uranus orbiter simply because the use case is speculative and radar is both heavy and places constraints on the trajectory (very close encounters are required).

In terms of seeing dark sides in uranus-shine, the geometry produces a quirky result. Near uranian solstice, half of each moon would be seen in daylight. Half of the other half could be lit favorably for uranus-shine observations. So, we might end up with 3/4 of each moon mapped.

Keep in mind that terrestrial telescopes are going to be able to observe uranian moons with increasing resolution as the massive South American telescopes come online in the next decade, so we might get some imaging of value to supplement whatever a mission would fail to see.

My suspicion for all of the above, though, is that we're whistling past the graveyard. I don't think Uranus or Neptune are going to get an orbiter until Europa, Titan, and Enceladus each have a turn or two in the queue, and we're talking about a good chunk of a century before that would run its course.

If the Breakthrough Starshot technology to visit another star goes anywhere, Uranus and Neptune might make some nice test cases, though.
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