all non-GEO power transmissions, since the incoming beam can arrive from widely different directions. A rectenna tilt angle is allowed for in the case of GEO satellite transmission. The slant range (S) and the beam elevation angle (E), measured at the ground plane, vary widely during a non-GEO transmission pass. In the calculation of beam coupling efficiency, the elevation angle is constrained to be greater than some specified minimum value - nominally 30°. This elevation mask accounts for possible local obstructions, and the fact that received power is significantly diminished at low elevation angles. figure 4-5 Geometric Parameters of Power Beaming Links In the case of the SunTower-to-Relay link, the basic operational assumptions are threefold: (1) the LEO SunTower utilizes a planar transmitter array in fixed orientation, pointed along the orbit plane normal (ie. toward or opposing the sun line); (2) the beam is steered electronically within the (a) constraint as described above; and (3) the relay satellite's ReflectArray is always nadir-pointing. These “non-tracking” ground rules greatly simplify the space system design requirements regarding pointing control, and also minimize the atmospheric drag and orbital debris impact effects on the LEO SunTower. However, they
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