New Frontiers 4: Argo? Options

[Mongo]

There does not appear to be a thread about this proposed New Frontiers mission, so I am starting this one. If there is an existing thread that I am unaware of, then by all means merge them.

Argo is a proposed outer solar system multiple flyby mission, rather like an updated Voyager mission, but based on the New Horizons bus, and using a similar instrument suite. It would launch between 2017 and 2019, with either a Jupiter / Neptune / KBO or a Trojan / Saturn / Neptune / KBO trajectory. Even a combined Jupiter / Saturn / Neptune / KBO trajectory is possible.

Neptune would present a much different system than in 1989, as telescopic observations show a more dynamic Neptune atmosphere, due to the change in season, and much more of Triton and the other Neptune satellites would be visible (most of Triton's northern hemisphere was in darkness in 1989, but will be well lit in 2030).

The second big payoff would be the vastly greater access to KBOs (~4000 times the accessable volume of New Horizons), with several already-known large KBOs (400km diameter or larger) within reach. The objects reachable with Argo are expected to include:

18 cold classical KBOs (interesting because they apparently formed in situ beyond Neptune's orbit, rather than further inward)
40 KBOs with diameters between 200km and 400km
9 KBOs with diameters greater than 400km
several binary KBOs

plus the possible Jupiter Trojan early in the mission. The wide expected range of choices allows for the selected KBO to be of very high scientific interest (and naturally, follow-on KBO targets could be selected after the primary KBO target has been selected).

Typical flight times from launch to the Neptune flyby are about 10 years (Jupiter gravity assist) or 13 years (Jupiter Trojan flyby), with the large KBO flyby 2 or 3 years later.

Expected cost including launch vehicle (according to the linked pdf): under $800M with the following strawman instrument package:

High resolution visible camera: New Horizons (NH) or reduced Cassini heritage
Near-IR spectrometer: NH heritage
UV solar & stellar occ. spectrometer: reduced Cassini heritage
Far-IR linear radiometer: Diviner heritage
Magnetometer: replaces NH dust instrument
Charged particle spectrometer: NH heritage
Gimballed high-gain antenna: heritage radio science instrument

The big uncertainty at this point seems to be the availability of plutonium-powered RTGs by the time of launch.

[Mongo]

According to this report entitled Radioisotope Power for NASA's Space Science Missions, New Frontiers 3 would be non-nuclear-powered; however Io Volcanic Observer would be a nuclear-powered Discovery-class mission. From Jason's site:

"NASA has commissioned several concept studies for Discovery-class mission that make use of the new Advanced Stirling Radioisotope Generator (ASRG) power source, a more efficient RTG that makes use of plutonium for power. One of these concepts is the Io Volcanic Observer (IVO), a mission to study Io's volcanic activity."

And this entry:

"NASA has decided to make two ASRGs available for the next Discovery-class mission, to be launched in 2013-2014. All previous Discovery-class missions have used solar panels for power. The cost of the RTGs will not be counted against the Discovery mission cost cap. [...] I had thought this was a study for a New Frontier-class mission. I didn't even think of this being a Discovery-class mission."

[vjkane]

"NASA has commissioned several concept studies for Discovery-class mission that make use of the new Advanced Stirling Radioisotope Generator (ASRG) power source, a more efficient RTG that makes use of plutonium for power. One of these concepts is the Io Volcanic Observer (IVO), a mission to study Io's volcanic activity." ... I didn't even think of this being a Discovery-class mission."

While this is being studied as a Discovery mission, I have doubts about whether or not this could be kept within a Discovery budget even with the free ASRG. Juno, which is about as simple of a Jovian orbiter as you can ask for (although a couple of the instruments are cutting edge), is ~$800m, which is ~$350m more than the Discovery price cap. I would love to see a Discovery Io observer but just have my doubts about the budget. Anyone out there more knowledgeable about this than I?

[Greg Hullender]

Juno, which is about as simple of a Jovian orbiter as you can ask for (although a couple of the instruments are cutting edge), is ~$800m, which is ~$350m more than the Discovery price cap.

Juno's an Atlas 551, not a 541, so it's a bit more expensive, but probably not $350m worth. ;-) From the Argos paper, an MRPG would cost them ~$35m, which is only 10% of the difference. Difficult to see where the rest would come from.

--Greg