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GLONASS M Satellites | L1 band 1602.5625 - 1615.5 MHz | L2 band 1240 - 1260 MHz |
---|---|---|
Number of Satellites | 24 | |
Approx. Distance, D, from Earth | 19,100 km | |
Semi-Major Axis | 25,440 km | |
Period | 676 minutes [8] | |
Polarisation | Right Hand Circular | |
Cesium Clocks Time Accuracy [3] | 1000 ns (1µs) | |
EIRP | 25 - 27 dBW | |
Antenna Gain | 11 dB | |
Beam Width (@ 3 dB ???) | ? (possibly ~ 36° [2]) | 38° [4] |
Bandwidth | 1 MHz (C/A carrier) 10 MHz (P carrier)^{*} | . |
Band Central Frequency | 1602 + n x 0.5625 MHz^{**} | 1246 + n x 0.4375 MHz^{**} [8] |
Max. Power Density [2] | -42 dBW/Hz (C/A carrier, 1601.5-1616 MHz) -52 dBW/Hz (P carrier, 1596.9-1620.6 MHz) | . |
Signal Strength | -161 dBM [8] | . |
For a transmitting antenna of power P_{a} (W), Feed losses L_{f} (dB), and antenna gain G_{a} (dBi), the maximum Effective Isotropic Radiated Power is given by:
EIRP_{max} = 10log(P_{a}) - L_{f} + G_{a} dBW [6].
Assuming that a receiver is located in the main lobe of the GLONASS beam, where the gain is G_{a}, the transmitter can be thought of as an isotropic antenna transmitting EIRP dBW into 4pi steradians. So the flux through a 1 m^{2} area on the surface of the Earth (19,100 km) over the entire transmitting bandwidth (in the main beam) will be 10^{EIRP/10} / (4*pi*(19.1*10^{6})^{2}) = 9.7*10^{-14} to 1.1*10^{-13} W.m^{-2} (for EIRP=25-27 dBW).
The Spectral flux (for the 1 MHz C/A carrier) will be 9.7*10^{-20} to 1.1*10^{-19} W.m^{-2}.Hz^{-1} (the flux of the P carrier will be an order of magnitude less than this).
1 Jy = 10^{-26} W.m^{-2}.Hz^{-1}. So this flux is equivalent to about 10^{7} Jy (in agreement with an NFRA prediction [7]).
If the back lobe gain of the receiver is to the order of -20 dB, then flux through the back lobe will be to the order of 100,000 Jy! This seems stronger than what is observed so there seems to be something major missing from this calculation.