TiME |
TiME |
May 13 2011, 12:55 PM
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#76
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Forum Contributor Group: Members Posts: 1372 Joined: 8-February 04 From: North East Florida, USA. Member No.: 11 |
Cat's are a law unto themselves, ours called "Chase" is no exception.
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May 13 2011, 01:39 PM
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#77
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Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
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May 15 2011, 08:44 AM
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#78
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Senior Member Group: Members Posts: 1729 Joined: 3-August 06 From: 43° 35' 53" N 1° 26' 35" E Member No.: 1004 |
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 |
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May 15 2011, 03:49 PM
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#79
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Solar System Cartographer Group: Members Posts: 10182 Joined: 5-April 05 From: Canada Member No.: 227 |
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 -------------------- ... because the Solar System ain't gonna map itself.
Also to be found posting similar content on https://mastodon.social/@PhilStooke Maps for download (free PD: https://upload.wikimedia.org/wikipedia/comm...Cartography.pdf NOTE: everything created by me which I post on UMSF is considered to be in the public domain (NOT CC, public domain) |
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May 15 2011, 05:20 PM
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#80
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Merciless Robot Group: Admin Posts: 8784 Joined: 8-December 05 From: Los Angeles Member No.: 602 |
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.
-------------------- A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
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May 15 2011, 09:11 PM
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#81
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Member Group: Members Posts: 599 Joined: 26-August 05 Member No.: 476 |
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. |
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May 15 2011, 10:39 PM
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#82
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
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).
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May 15 2011, 10:49 PM
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#83
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Senior Member Group: Members Posts: 3516 Joined: 4-November 05 From: North Wales Member No.: 542 |
I'm on board. There's no fatal flaw with the mission. Bring it on and reveal the chemistry.
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May 15 2011, 11:07 PM
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#84
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IMG to PNG GOD Group: Moderator Posts: 2251 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
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.
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May 15 2011, 11:39 PM
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#85
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Senior Member Group: Members Posts: 1584 Joined: 14-October 05 From: Vermont Member No.: 530 |
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. |
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May 15 2011, 11:53 PM
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#86
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Member Group: Members Posts: 796 Joined: 27-February 08 From: Heart of Europe Member No.: 4057 |
"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. -------------------- |
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May 16 2011, 01:08 PM
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#87
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Newbie Group: Members Posts: 16 Joined: 30-March 08 Member No.: 4078 |
Except that the vast majority of the data will probably be GCMS results, which are a little less photogenic, albeit very scientifically valuable.
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May 16 2011, 02:16 PM
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#88
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Senior Member Group: Members Posts: 2173 Joined: 28-December 04 From: Florida, USA Member No.: 132 |
...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? |
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May 16 2011, 03:08 PM
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#89
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Member Group: Members Posts: 214 Joined: 30-December 05 Member No.: 628 |
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.
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May 16 2011, 03:10 PM
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#90
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Senior Member Group: Admin Posts: 4763 Joined: 15-March 05 From: Glendale, AZ Member No.: 197 |
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. -------------------- If Occam had heard my theory, things would be very different now.
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