Uranus Orbiter, The other proposed ice-giant mission Options

[Rob Pinnegar]

Since the Neptune Orbiter thread has started to veer into talking about a Uranus orbiter as well, it seemed like a good idea to start a topic for Uranus.

[Spirit]

Maybe we'll have another opportunity to flyby Uranus earlier. I am pointing to the Jupiter Flyby with Probes and Saturn Flyby with Probes missions. If they get launched at the right time and have a technical capability to operate at Uranus orbit, we might be lucky. Yeah, we have a bunch of problems like power supply, telecommunications and money, but who knows.

[JRehling]

Maybe we'll have another opportunity to flyby Uranus earlier. I am pointing to the Jupiter Flyby with Probes and Saturn Flyby with Probes missions. If they get launched at the right time and have a technical capability to operate at Uranus orbit, we might be lucky. Yeah, we have a bunch of problems like power supply, telecommunications and money, but who knows.

Jupiter Flyby with Probes has most of the life taken out of it by Juno. Although an orbiter is technically a very different mission profile than a flyby with entry probes, Juno addresses many of the science goals that the multi-probe mission would have pursued. The AO for the New Frontier mission to Jupiter sort of expected entry probes but had a loophole that allowed a good remote-sensing mission to replace the actual entry probes, and Juno successfully convinced the powers that be that it will get the job done from orbit.

A Saturn entry probe is not what I'd call high on the list of missions to fly, but it is desirable sooner or later. When it does fly, it *could* work out that the bus/flyby craft could take a trajectory to Uranus (or Neptune, or some KBO), but I think the trajectory may be constrained by the need to get gravity data from the Saturn flyby.

On the other hand, Cassini might be able to fulfill that goal with a close dip over the cloudtops one or more orbits before its death plunge.

The Saturn flyby craft would *still* presumably have trajectory constraints as a data relay, etc. To my mind, top-down constraints would encourage planners to FIND a way to see two planets with the same mission, where feasible, and I don't think missions get enough credit for fulfilling off-prime science goals when selection time occurs. The Uranus flyby would have to end up coming almost for free, because if it increases the requirements (besides, obviously, a ground crew and DSN time) for a Saturn mission, it's going to be very unlikely.

To my mind, a $50 million (say) cost increase to a Saturn mission so it could fly by Uranus is like a $50 million mission to Uranus. But with bottom-up planning, that only looks like a complication of the "main" mission.