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First broadcast TV satellite's orbit

  1. Jul 28, 2009 #1


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    I noticed on Modern Marvels that they mentioned sometihng about hte first satellite put up for broadcast TV transmission. I think. They mentioned it had an oblong orbit that allowed it to be within tranmission range for only 20 minutes every 24 hours. Why was this? Was there limitations back in the day that prevented geosynchronous orbits?

    Maybe this belongs in the engineering area... but that place scares me.
    Last edited: Jul 28, 2009
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  3. Jul 28, 2009 #2

    D H

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    Signal strength and launch technology. Telstar I and II were tiny and had very limited receiving and transmission power. The ground antennas were huge. A newspaper ad from the time:


    Larger version: http://farm1.static.flickr.com/39/96879628_a95cb1b8ef_o.jpg

    The ground antenna horn is shown in the lower left. That little spec near the rim of the horn is a man. This thing was huge! It had to slew at 1.5 degrees per second and maintain a pointing accuracy of 0.06 degree, per the http://en.wikipedia.org/wiki/Telstar" [Broken].
    Last edited by a moderator: May 4, 2017
  4. Jul 28, 2009 #3


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    The US ground station was located only a few hours from my HS, so we took a fiend trip to see it. Massive horn antenna!
  5. Jul 28, 2009 #4


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    It was probably 20mins every orbit (2 1/2 hours).
    I think using MEO was more a funtion of transmitter power than rocket technology. Geo-stationary orbit is 20,000 miles so you would need 400x the signal strength of a 1000mi orbit. Telstar was very low power and needed huge radio dishes already.
  6. Jul 28, 2009 #5


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    Ah yah, I wasn't paying much attention, 2.5 hours sounds similar to 24 hours! Well that makes sense, I didn't think of that.
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