Space Based Solar Power Radio Interference

Work in progress, may be many errors

The Analemma

A lightweight space power satellite under light pressure cannot remain in a stationary spot without large expenditures of delta V. Similar to a server sky array, it will need to be in an elliptical orbit, with perigee towards the sun. Assume 15e6 m² area and 40e6 kg, sail ratio 0.375 for a big SSPS array. GEO circular orbit velocity (sidereal) is 3075 m/s. The eccentricity is 3 * 4.56e-6 * 0.375 * 3.156e7 / 4 π 3075 = 4.2e-3 .

Space Power Satellite Bands

Broadband satellite systems typically employ the 27.5-30.0 GHz SHF frequency range for uplink transmissions (earth-to-space) and the 17.7-20.2 GHz range for downlink transmissions (space-to-earth)

Distance from GEO to 45N, 38000 km, 1.8e16 m². 1W EIRP produces 5.5e-17 W/m² or 5.5e-18 mW/cm² at antenna dish.

2GW powersat produces 30mW/cm², 300W/m² an EIRP of 187 dbW on beam. Sidelobe power is 0.01mW/cm² or 0.1 W/m², an EIRP of 153 dBW, and the "floor" is 100nW/cm², 1μW/m², an EIRP of 103 dBW.

I don't know how much we must filter this spike of energy to keep it from degrading a signal. Chances are, a pure tone won't land directly in the signal band, but nonlinearities in LNA and mixer could shift the frequency into the baseband. Let's be very optimistic and assume that we can tolerate a signal or harmonic of the same power as the comsat signal.

If rectennas are as simple as a vast field of dipoles and diodes, then they will make a huge third and fifth harmonic emission; they will not be all-frequency zero emission surfaces. So, they will reflect some first harmonic energy away from GEO, but the third and fifth harmonics will form a dense array of very high power grating lobes, scanning through the sky as the incidence angle of energy from the powersat changes, as it follows its daily analemma.

Satellites in GEO

http://www.itu.int/snl/freqtab_snl.html