XPost: sci.astro, sci.astro.amateur   
   From: george@briar.demon.co.uk   
      
   "hankman"  wrote in message   
   news:mEfHd.822$Xz5.56745@wagner.videotron.net...   
   >I still do not have a clear picture of exactly what was lost due to the   
   > glitches with the data channel on Huygens. Most reports just barely   
   > mention   
   > the glitch and most do not even mention it and none are clear on just what   
   > data was lost and what was recovered, and how it was recovered.   
   >   
   > Some seem to indicate that nearly nothing was lost due to the fact that   
   > the   
   > channels were redundant and the data was duplicated over both channels.   
   > Others seem to indicate that the "recovered" data was due to the   
   > "eavesdropping" of the earth-based radio telescopes. Yet other reports   
   > seem   
   > to indicate that half (some 350 of 700) the images were completely lost   
   > (and   
   > not recovered by some other means such as redundancy of channels or   
   > eavesdropping from earth).   
   >   
   > Can anyone shed some light on these issues and why the media seem shy to   
   > dwell more on these matters as well on the notable successes of the   
   > mission.   
      
   >From comments made in the press conference, the original   
   intention was to copy the data on both channels so if   
   one was lost, the data still got through. What was said   
   led me to believe that happened for all the instruments   
   other than the camera.   
      
   For the images though, someone decided to use the channels   
   separately which was probably a good idea. I don't know what   
   the actual rate was but for illustration, instead of taking   
   say one picture every 30 seconds and sending it through both   
   channels you can take one every 15 seconds and send them   
   through alternate channels. In one channel dies, you still   
   get one picture a minute so you are no worse off but if both   
   channels work you get twice as many images instead of two   
   copies of each. The press would ignore it as the consequences   
   are minimal.   
      
   George   
      
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