First broadcast TV satellite's orbit

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Discussion Overview

The discussion revolves around the first satellite used for broadcast television transmission, specifically focusing on its orbit characteristics and the technological limitations that influenced its design. Participants explore the implications of the satellite's oblong orbit and the reasons behind the choice of medium Earth orbit (MEO) over geostationary orbit.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that the first broadcast TV satellite had an oblong orbit allowing it to be in transmission range for only 20 minutes every 24 hours, questioning the limitations that led to this design.
  • Another participant attributes the limited transmission range to signal strength and the technology of the time, mentioning that Telstar I and II were small satellites with limited power, necessitating large ground antennas.
  • A participant shares a personal experience visiting a ground station, emphasizing the size of the horn antenna used for reception.
  • Some participants suggest that the choice of MEO was more related to transmitter power requirements than to the capabilities of rocket technology, noting the significant difference in distance and required signal strength between MEO and geostationary orbits.
  • One participant corrects their earlier misunderstanding about the duration of the satellite's orbit, clarifying that it was approximately 2.5 hours rather than 24 hours.

Areas of Agreement / Disagreement

Participants express differing views on the reasons for the satellite's orbit choice, with some attributing it to technological limitations while others emphasize the power requirements. The discussion remains unresolved regarding the primary factors influencing the design decisions.

Contextual Notes

Participants discuss the limitations of early satellite technology, including signal strength and the size of ground equipment, but do not resolve the specifics of these limitations or their implications.

Pengwuino
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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.
 
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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:

96879628_a95cb1b8ef.jpg


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" .
 
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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!
 
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.
 
mgb_phys said:
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.

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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