TiME Options

[MahFL]

Cat's are a law unto themselves, ours called "Chase" is no exception.

[djellison]

So did the Endurance. But thanks to Shackleton's heroics, everyone on board survived.

Heck, call it James Caird.

[Paolo]

a technical question: any idea of the data rate of TiME and of the amount of data expected from the primary mission?
I get the impression that there will not be enough bandwidth for serious imaging

[Phil Stooke]

My concern too - coupled with the brief mission after a long silent cruise (no flyby science at Jupiter) - makes me prefer the other options.

Phil

[nprev]

On the other hand, it's gonna have gobs of power, WAY more than, for example, the MERs & other solar-powered spacecraft. I imagine that TiME might run dual-transmitter during the primary mission as is planned for NH, which should provide adequate bandwidth for image & data return.

[mchan]

Just because TiME will use an ASRG (or two) does not necessarily mean more power than a solar-powered soacecraft. It is independent of distance from Sun. But then it will also be at Saturn distance, not quite as far as NH will be, but still much farther out than MER. As with solar flux, comm power goes down by inverse square of distance, and TiME will not have a big high gain antenna. To a first order, my guess is TiME comm bandwidth will be an order of magnitude less than that of Cassini.

Since it will be out of line of sight to Earth for at least half of Titan's orbit, TiME may use rechargeable batteries to increase peak power during the times it can transmit to Earth similar to MSL for driving.

[Bjorn Jonsson]

An extremely crude back-of-the-envelope calculation: Assuming an antenna/transmitter comparable to Cassini's but 10 times smaller you get approximately 1000 bps. That's over 10 times the typical Galileo rate on a spacecraft with fewer instruments where everything is designed with that data rate in mind, unlike the case with Galileo. Of course, lacking more information, this is all highly uncertain but it seems to me the data rate must lie somewhere between 100 and 10,000 bps and even the lower number gives you a great mission (just look at Galileo).

[ngunn]

I'm on board. There's no fatal flaw with the mission. Bring it on and reveal the chemistry.

[Bjorn Jonsson]

Thinking more about this, the Galileo LGA might be a better analogy than Cassini's HGA since it would probably be difficult to aim a narrowly focused signal to Earth. But even that should give you a respectable data rate for a mission like this.

[stevesliva]

And of course, as long as the descent imaging and initial panos can be stored, some have said the view might not change all that much.

Might be cool to watch for weather, though. Clouds and fogbanks. But that can be done with thumbnails and highly compressed images to see whether there's weather.

[machi]

"any idea of the data rate of TiME and of the amount of data expected from the primary mission."

In very similar Titan Lake Probe study was DTE data rate 400 Mb/32 days. This is around 500 bits/s, relatively nice data rate from such great distance.
For 3-months primary mission it's approx. 1.1 Gb. For example, this is equivalent of 400 1 Mpix images with lossless compression or around 2000 images with lossy compression.

[JGodbaz]

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

[centsworth_II]

...Since it will be out of line of sight to Earth for at least half of Titan's orbit, TiME may use rechargeable batteries to increase peak power during the times it can transmit to Earth...

Maybe out of sight less than half Titan's orbit. How long would Titan actually be behind Saturn, or close enough to prevent communication?

[tanjent]

Good point. Roughly speaking the Earth should be visible for about as long as the sun; from the polar regions basically 'round the clock until the next equinox. It will be getting pretty close to the horizon, though.

[ElkGroveDan]

I suppose engineering specifics are way down the road on this, but I can't help but wonder what kind of materials and design they are going to use for the "hull" of this vessel. It's been a few decades since I studied materials science, but intuitively it would seem that it's going to be difficult to isolate the heat from whatever warm-electronics-box will be buried in the craft's interior, not to mention protruding instrumentation. Compared to the temperatures internal to most spacecraft, it wouldn't take much to nudge the outer structure a couple of degrees above the boiling point of the liquid it will be floating in (-250 -260 F or whatever the exact figure is).

The other issue that comes to mind is the mechanical characteristics of whatever outer cryo-materials will be used. They are going to need structural members that will survive launch vibration conditions and still retain or resist changing ductility and brittle conditions over such a wide temperature range during and post-EDL. It's going to be a fascinating process and I can't wait to read about the engineering challenges and solutions.