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jaydeehess
2005-Jan-17, 03:01 AM
(did I spell that correctly?)

How are the images transmitted from Saturn to Earth? I notice that the release of images seems to be rather slow and that is why I ask. I suppose that the data is sent several times and processing is then done to eliminate as much noise as possible but I am guessing.

If this has been answered in the other threads, sorry but I couldn't think of how to phrase a search for this specifac topic.

01101001
2005-Jan-17, 03:47 AM
(did I spell that correctly?)
Spelled it right... but can you pronouce it right?


How are the images transmitted from Saturn to Earth? I notice that the release of images seems to be rather slow and that is why I ask. I suppose that the data is sent several times and processing is then done to eliminate as much noise as possible but I am guessing.
Transmitted digitally, no doubt in data packets, at 35 kilobits/second. All the Hyugens data got here over a short, reasonable time. I think they sent it 6 times total for redundancy, with multiple listeners, just in case of bad weather or a snafu at some receiver. The release of images is done, happended just hours after Huygens generated them and passed them onto Cassini, and were distributed fairly quickly once on Earth. Those are the raw images. They're all over the Net now.

ESA is processing those images and will no doubt release the improved versions, the composites, the mosaics, the animations, over time, as they add value.

I'm not sure what noise you refer to. There is noise at many stages.

jaydeehess
2005-Jan-17, 05:53 AM
Thanks. Actually I just watched a Discovery Ch. special that came on after my post that answered my question.

Huygens(pronounced Hue-gens in Disc. though I have also heard hoy-gens)


I'm not sure what noise you refer to. There is noise at many stages.


I was referring to comparison of each transmission of the same picture which would enable processing that could reduce the noise.
ie. a data bit that in 2 transmissions is a "1" but in the other 4 is a "0" would most likely actually be a "0"

I fully understand that there are many places along the route where noise can be introduced, both extra-terrestrially and closer to home.

01101001
2005-Jan-17, 06:41 AM
Huygens(pronounced Hue-gens in Disc. though I have also heard hoy-gens)
For fun, see Cassini-What? (http://www.badastronomy.com/phpBB/viewtopic.php?p=389866) if you want a pointer to an mp3 of how a Dutch person might promounce it.



I'm not sure what noise you refer to. There is noise at many stages.

I was referring to comparison of each transmission of the same picture which would enable processing that could reduce the noise.
ie. a data bit that in 2 transmissions is a "1" but in the other 4 is a "0" would most likely actually be a "0"

I fully understand that there are many places along the route where noise can be introduced, both extra-terrestrially and closer to home.
A packetized digital transmission should get the bits right. Each packet should include extra error detection/correction data, a sort of checksum, that would indicate errors in the packet, and even provide enough redundancy to resurrect a small number of bit-errors. A Cassini Q&A (http://quest.arc.nasa.gov/saturn/qa/cassini/Error_correction.txt) says the bit-error rate is 1/miliion -- but I don't know if that's then correctable with retransmission requests for the bad packets. It should be. With the Huygens data transmitted 6 times for safety, they probably didn't even have to request any retransmission. I'm sure they got everything Cassini sent almost immediately. I can't imagine there's any laborious post-processing to fix transmission errors. It didn't slow the release of the raw images. That happened pretty fast -- except to the masses when Internet servers were swamped at first.

Sticks
2005-Jan-17, 10:59 AM
Another question

How much did this cost?

I remember some days after the Mar's rover mission someone in a local rag condemned the mission as the money could be better spent here on Earth feeding the poor and the hungry etc... :-s

Hamlet
2005-Jan-17, 03:01 PM
Another question

How much did this cost?



According to this article (http://spaceflightnow.com/cassini/040612hurdles.html):


When all was said and done, NASA spent $2.6 billion on the project, the European Space Agency spent $500 million and the Italian Space Agency chipped in $160 million for a total cost of about $3.26 billion.




I remember some days after the Mar's rover mission someone in a local rag condemned the mission as the money could be better spent here on Earth feeding the poor and the hungry etc... :-s

Yes, I remember these too. This seems to be a recurring theme since the dawning of the space program. It's naive to think that the space program is taking food out of anyones mouth. It's also a bit naive to think that money from a defunct space program would automatically go to poor people. There are a lot of reasons for poverty and hunger, but the space program isn't one of them.

Disinfo Agent
2005-Jan-17, 03:12 PM
[Edited. Redundant post. #-o]

Nicolas
2005-Jan-17, 03:18 PM
Now that you've all mastered the pronounciation of "Huygens" with this MP3, I'll tell you that it is pronounced somewhat different in Belgian Dutch.
(After you've mastered that, we'll start with the dialects). :D