rf energy to de. Estimates of the power densities at the surface of the earth from a single SPS are shown in Table 2. Table 2. Approximate Power Density of the 2.45 GHz _ ___________ _ _________ Fields at the Surface of the Earth_____________________ It should be noted that these estimates apply only to the 2.45 GHz fundamental signal. Signal levels at the surface of the earth due to out-of-band noise and harmonic radiation are significantly different. In the event multiple satellites are placed in orbit, the exposure levels outside of the main beam can be significantly altered due to overlapping of sidelobes from adjacent beams. For 60 orbiting SPS satellites, a typical average exposure level for locations well removed from an SPS rectenna site would be of the order of 10 mw/cm . The characteristics of the interference fields at a frequency other than 2.45 GHz are largely unknown. Estimates of the fields due to SPS harmonic and noise emissions are described in a separate report. (The report "Analysis of interference between the solar power satellite and conventional satellite systems," by J. R. Juroshek, is being prepared for publication as an NTIA Technical Report.) This report estimates that noise in frequency bands + 50 MHz from SPS could be as high as 10 mw/cm . Estimates of signal levels at 2nd, 3rd, and 4th harmonics at the earth surface range from 10 to 10 mw/cm . The variability in these estimates is due to an uncertainty in the gain of the SPS transmit antenna at
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