Satellite Communications/G/T constellation

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Question
Hello,
Hope you are doing good.

How do I get the G/T constellation (G/T values spread across the beam coverage) for a particular beam.I searched for the same on satellite providers website and other online media but could not find the same.

Thank you in advance.

Answer
Mayur:

I assume that you are interested in G/T for a ground antenna such as a VSAT terminal.

The following Wikipedia has a good description of antenna gain-to-noise temperature. http://en.wikipedia.org/wiki/Antenna_gain-to-noise-temperature.  

Although the article does not mention it, the antenna temperature will vary with antenna pointing angle. If pointed at zenith, the main beam sees the 4 Kelvin sky and the back lobe sees the warm Earth. When pointed at the horizon, the main beam sees both 4 Kelvin sky and warm Earth; the side lobes, which have substantially higher gain than the back lobes, will see the warm Earth.

Here is a link to a G/T calculator. http://www.satcom.co.uk/article.asp?article=23. Unfortunately, it uses one value of G at a time; it does not use a gain distribution, which you will need to calculate the G/T constellation.

I am sorry that I cannot be of more assistance. There were no details in your question: antenna diameter, frequency, details about the RF string behind the antenna, details about satellite pointing and if pointing is fixed versus tracking.

Regards,

Thomas E. Burke, PhD, PMP

Satellite Communications

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Thomas E. Burke

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Experience

Forty years of experience with satellite communications. Have held roles as system engineer on JPL Mariner 9 program and a program manager for a number of classified communication satellite programs. Served as head of TRW / Defense Communications Division / Engineering Development Operation, a 1,400-person organization responsible for all aspects of classified communication satellite design and development.

Education/Credentials
Ph.D. Chemistry, California Institute of Technology (1969) B.A. magna cum laude Chemistry, University of Minnesota (1962)

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