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Posted by: jasedm Jan 19 2017, 09:19 PM

I would personally love to see this.

Would it be possible to insert a probe into an orbit that is very slightly (a couple of degrees or so) above the ring-plane, and start out after insertion burn around Enceladus' orbit. The probe could conduct a set of detailed studies there before with repeated burns, spiralling slowly inwards, thereby intersecting the orbits of Mimas, Janus/Epimetheus, and so on, before skimming a few kilometres above the rings all the way in.
At ~5km or so above the ring plane with a very decent camera might it be possible to resolve individual ring particles in the order of a few tens of metres?

Posted by: fredk Jan 19 2017, 09:35 PM

Do you mean can a probe orbit parallel to, but outside of, the rings? If that's what you mean, the answer is no. Anything orbiting Saturn must be coplanar with Saturn's centre of mass, according to Newton. So you'd have to intersect the ring plane somewhere. I think the best you could do would be to cross the ring plane just outside the rings or in a ring gap.

Staying parallel to but outside the ring plane is possible if you apply thrust to keep you there, but I don't think you could do that for long with reasonable amounts of fuel. But that's not entirely clear to me, since the fuel required would drop the closer to the rings you got. So a path just 100 metres, say, above the ring plane may not require much thrust. That's a calculation someone could probably do...

Posted by: Explorer1 Jan 19 2017, 09:57 PM

Are any of the ring gaps actually clear enough for a probe to stay in and be safe from particle impacts? They would be hopefully low velocity, and we know that Rosetta survived a long period inside a similar environment without any need for shielding.
Or perhaps just a much more powerful camera (say HiRise style) on a future orbiter with a similar trajectory, so still keeping a safe distance while getting better resolution? Just wild speculation here...

Posted by: jasedm Jan 19 2017, 10:03 PM

Yes - excuse my ignorance I imagined a fairly decent bi-propellant engine for orbit insertion and major orbit-tweaking burns, and an ion engine to gently nudge and shape the orbit, achieving a continuous inward spiral.

Posted by: HSchirmer Jan 19 2017, 11:40 PM

Hmm, a light sail to allow some above-the-rings station keeping?

Posted by: mchan Jan 20 2017, 01:54 AM

A spacecraft that crosses the ring plane in the clear outside of F-ring and inside of D-ring with a very low inclination would have a "ring-skimming" orbit. It would be closest to the rings (edge of F- and D-rings) at apoapsis and periapsis and farthest from the rings (somewhere in middle of B-ring) near midpoint between apoapsis and periapsis.

The spacecraft would alternately skim over the north side and south side of the rings over half the orbit. At any time other than equinox, half the orbit would be over sunlit side and half would be over backlit side (discounting the passage thru Saturn's shadow). Guesstimate orbital period under 12 hours. Power, communications, and image smearing are probably challenging.

Posted by: toddbronco2 Jan 26 2017, 04:28 PM

There actually was a very interesting proposal called the Saturn Ring Observer that was planned to do exactly what you just suggested; Using low-thrust electric propulsion to maintain a perpetual small offset above the rings as it slowly spiraled in toward Saturn.

http://sites.nationalacademies.org/cs/groups/ssbsite/documents/webpage/ssb_059328.pdf

Posted by: Holder of the Two Leashes Jan 26 2017, 06:56 PM

Hmmm. I wonder if anyone has looked into the feasibility of using an electric tether to hold a spacecraft up above the rings using Saturn's magnetic field? If it could be done, that part at least (hovering) could be propellantless. I couldn't find any mention of it in the study paper.

Posted by: nprev Jan 27 2017, 03:10 AM

This thread is for discussion of possible future missions to study the rings. Please review rule 1.9 re SF engineering before posting. Have fun!

Posted by: Holder of the Two Leashes Jan 27 2017, 02:08 PM

Just a quick note to clarify that discussions of using electric tethers to alter orbits does not fall under rule 1.9. A Japanese HTV cargo craft on its way down from the ISS is going to test one out next week, in fact.

ADMIN: Technologies in active development like that are fine. Fusion rocket motors, warp drives and such are not.

Posted by: scalbers Jan 27 2017, 06:09 PM

I recall tethers were tested quite some time ago on the ISS as well (though this might bump into Rule 1.1).

Posted by: HSchirmer Jan 27 2017, 07:27 PM

Hmm, what about a orbit around the L1 point of Mimas?

Then keep skipping into the rings along the L1 points of smaller and smaller satellites,
Mimas, Epimethius, Prometheus, Pan?