TiME Options

[centsworth_II]

...the Earth should be visible for about as long as the sun; from the polar regions basically 'round the clock until the next equinox....

Titan will still go behind Saturn every 16 days as it orbits. But the actual time that Saturn blocks signals should be very short. Based on Saturn radius of 60,000 km and Titan orbit radius of 1,200,000 km, I calculate that Titan is blocked by Saturn for less than 1/60th of its orbit.

[Bjorn Jonsson]

Titan will still go behind Saturn every 16 days as it orbits.

This only happens near the time of the Saturnian equinox as seen from Earth.

[centsworth_II]

This only happens near the time of the Saturnian equinox as seen from Earth.

So it won't happen at all during the TiME mission?

[Bjorn Jonsson]

No, it won't happen (unless you get a *very* long extended mission).

[helvick]

Dan - I wouldn't have thought that sort of temperature isolation would be an insurmountable technical challenge provided you don't want to put any active components on the outside of the hull. The JWST has active components sitting in the cryosection at around 35K connected to the ISIM (the Integrated Science Instrument Module) that operates at ambient (300K) via a 4m cable that requires some serious engineering so it is possible but I suspect that the mass of the multi-stage cooling system required to allow that would not be possible on TiME.

[centsworth_II]

No, it won't happen (unless you get a *very* long extended mission).

So, if TiME really is above the horizon (from Earth) for the length of the mission, and Saturn never blocks the line of sight, then TiME should be able to transmit data constantly throughout the three month mission. There may be technical or logistical reasons why this is not possible, I don't know, but it should be theoretically possible, I imagine.

[nprev]

One thing to consider is that TiME will require VERY long periods of DSN use since the bitrate is going to be relatively low. That may be as much of a limiting factor as anything else.

[rlorenz]

Except that the vast majority of the data will probably be GCMS results, which are a little less photogenic, albeit very scientifically valuable.

I'm glad to see that you lot are thinking about all this - fun, isnt't it?

Obviously I'm not going to go into specifics but it is possible to address some of the questions that have
come up in very general terms.

Materials/temperatures - guys, come on. Huygens operated in this environment until its batteries ran
out. Launch vehicles - to say nothing of the liquified natural gas industry - deal with cryogenic fluids
all the time. Of course heat leaks and insulation need to be designed appropriately, and material
properties at the relevant environment must be considered, as they do on Mars and Venus or in vacuo.

Communications - some cogent discussion on the thread. This has been thought about a lot for Titan
balloons too. I'll remind readers that many cruise ships, and drones for that matter, use gimballed
antennas for satellite communications. Again, not trivial, but a familiar and soluble problem.

As for data - have a look at the Huygens or Pathfinder or any other mission's balance of data volume
between imaging, composition, meteorology etc. On any mission this balance gets struck somehow (and
indeed it can often be tuned during the mission)

[ElkGroveDan]

Materials/temperatures - guys, come on. Huygens operated in this environment until its batteries ran
out. Launch vehicles - to say nothing of the liquified natural gas industry - deal with cryogenic fluids
all the time.

Thanks for responding Ralph. My actual concern was not so much the low temperatures affecting the TiME craft as the other way around. If it drops down in that hydrocarbon sea and then sets it boiling and steaming that would seriously affect instrumentation's ability to collect data would it not? If nothing else images would be difficult. With respect to terrestrial cryogenic industrial uses, to the best of my knowledge none of that equipment is required to go through launch vibration tests at STP and then transition to high loads and stresses in cryogenic environs. My armchair recollections are that materials which are strong and ductile at one end become fragile and brittle at the other end and vs. vs. Certainly the temperatures we are dealing with are substantially lower than any of the Mars craft were designed for, and then finally the whole notion of the vehicle in contact with an ocean of liquid adds a heat capacity component to the materials calculations that is barely a factor in the gaseous 0.01 atm on Mars.

I'm certainly not questioning your knowledge or understanding of the conditions (I read your book), just outlining my line of thinking that caused me to pose (perhaps in-artfully) the previous question.

[rlorenz]

Thanks for responding Ralph.
.....
I'm certainly not questioning your knowledge or understanding of the conditions (I read your book), just outlining my line of thinking that caused me to pose (perhaps in-artfully) the previous question.

Dan

I realize your questions are well-intentioned and motivated by your excitement about this mission (an excitement
that is widely shared). The fact is that any measurement perturbs its subject (qv quantum theory)
and this applies to a warm lander on Titan, a warm lander on a comet, or a geophysical lander on Mars that couples
wind energy into the ground.

It is also a fact that a Phase A study is just that, a study. Only one of the three missions under study is likely to fly (and NASA
reserves the right not to fly any of them!). Remember too that USMF is read by many in the planetary science community.
Thus people who may be reviewing study reports in the future and deciding what flies could be reading your question.
Developing a full answer that satisfactorily addresses your question (or any other from someone else) may require more text than
most people want to read, more of my spare time than I can afford, or may require details that are proprietary to
my employer or one or more of the industrial/agency/academic partners in the project. So a complete answer cannot
be given, and an incomplete answer may be seen as indicating a weakness that may not exist or may be otherwise
taken out of context.

Thus by asking a question of a mission in competition in a public forum you actually may make
the mission less likely to happen. There does not exist at present a 'people's court' wherein missions under competition
can be probed by the public in an equable manner, appealing as such a notion may be (and it may not appeal for example
to industry). And probing at concepts under study in an ad-hoc manner, wherein all concepts under competition are not probed
equally, could be prejudicial to the decision-making process. So I ask your understanding that I cannot discuss such details.

All I can say is the challenges of doing science in an exotic environment are recognized by a team that has successfully
addressed such challenges before. The detailed plans for doing so will be evaluated in NASA's formal review process.

And let me take this opportunity to remind readers that (roughly) for every scientist out there doing cool stuff like studying
pictures on Mars, or analyzing bits of asteroids, there's another (nameless) scientist who doesnt get their name on papers, or appear
on TV, but who had to sit on a tedious peer review panel for a week in some dreary hotel, and read hundreds of pages of dense proposal
material to help judge which 1 of 5 scientists should be picked to work on the team, or which mission should fly, when
actually the top 3 out of the 5 would all be superb. A painful decision, and an onerous duty, but one that is rarely
recognized outside the field.

[nprev]

One overarching thought: Somebody, sometime, has to be the one to do any given thing first for any given situation.

TiME would be one of the most memorable of those in my lifetime.

I suspect that the general public will feel much the same.

(Damn right this is a shameless plug!!!)

[ngunn]

Thus by asking a question of a mission in competition in a public forum you actually may make
the mission less likely to happen. There does not exist at present a 'people's court' wherein missions under competition
can be probed by the public in an equable manner, appealing as such a notion may be

Ralph, as ever your insights are most welcome and highly prized here. There is no 'people's court', and yet inevitably there is bound to be some kind of 'people's court in exile', articulated in small part on this forum. You say that posing questions here may have a damaging effect. Let's hope enthusiastic support can work the other way. I think it's pretty clear you already have the majority of the jury.

[ElkGroveDan]

Thanks Ralph. Really just curiosity on my part. I am fascinated by physical challenges and cutting-edge solutions. I am grateful for your willingness to share with us when you can. Best of luck with this.

[toddbronco2]

I think it's "time" for TiME to graduate to its own Saturn thread instead of being forever buried in the Cassini Huygens sub-threads.

[rlorenz]

I think it's "time" for TiME to graduate to its own Saturn thread instead of being forever buried in the Cassini Huygens sub-threads.

Hmm, perhaps. It even gets a mention on xkcd today......

http://xkcd.com/1074/