What does G/T ratio of antenna signify?

[atul_microwaves_antenna]

Hello All,
I am bit digging up topic of Antenna Gain/ Antenna(System) Temp. It is popularly known as G/T ratio of an antenna and it is one of the very important parameters for antennas used in Satellite communication.
I wonder what dose it really signify? Better the G/T ,better the antenn, it simply means that lower the Antenna temp(noise) .Also better the G/T higher the effective aperture of an antenna.It is all about a ratio analysis.But I wonder I one uses this G/T ratio to design an antenna? a receiving antenna...?
Thank you..

 

[toonafishy]

g?t ratio

antenna gain-to-noise-temperature (G/T): In the characterization of antenna performance, a figure of merit, where G is the antenna gain in decibels at the receive frequency, and T is the equivalent noise temperature of the receiving system in kelvins. The higher this ratio the better the sensitivity of the system to weak signals.