Neptune Orbiter, Another proposed mission Options

[Rob Pinnegar]

This seems like a good place to start off the Uranus and Neptune forum: with the next ice-giants mission.

I will admit to not knowing a whole lot about the Neptune Orbiter With Probes (NOWP), other than the fact that it's in the planning stages, and a few other details I've gathered from Wikipedia and various other Internet sources. Anyone care to get this one going with a bit more information?

[nprev]

Nereid: 27.6 deg with respect to Neptune's equator, orbital period 360 days, eccentricity 0.75(!)
Triton: 157.35 deg

Not easy, but not impossible if it's done as a one-time-only good deal at system entry like Cassini's Phoebe encounter, I think; arrival timing would be everything. Getting out there again after entry into orbit even when Nereid is near periapsis (esp. if Triton is the prime focus, which is probable) seems unlikely in the extreme, esp. because the relative velocity would probably be pretty bad (Kepler strikes again!)...image smearing would be a significant concern, for example. Besides, Proteus is larger, probably more interesting, and far more accessible; I'd expect Nereid to be a lot like Phoebe.

[JRehling]

It's odd that people brought the topic of Nereid up this week -- I was just thinking about the same issues.

Here's the key fact about Nereid: It rotates. You don't need to have multiple flybys to see most of its surface.

If geometry permitted, the ideal situation would be to find Nereid near its apoapsis while the craft were still en route to Neptune. It could make a leisurely approach while Nereid also approached Neptune, and could make close observations over a span of 12 hours. That alone would reveal most of Nereid's surface. Then, why fly by again?

With a periapsis four times Triton's, there's no need to have the Neptune orbiter ever venture out so far again. The other "major" satellites are all well inside of Triton's orbit. Unless the energy to keep the orbit in so tight cannot be spared, it should head inside and never venture out again. Most likely, the non-Triton satellites are minor priorities themselves. Gettings lots of looks at Triton (active over time), Neptune (active over time), and the rings (active over time) would comprise 85% of the mission.