Fig. A-l. Antenna Efficiency Curve (Derived Hyperbola) as a Function of Microwave Radiator Cost for 10 km Diameter Lunar Antennas. Open mesh antennas operating at such efficiencies are probably feasible and can provide substantial savings over waveguides when radiator surface areas are as large at the 87 km2 LPS antenna. The waveguide cost estimated in Table 1 ($35,600.0 million) might be considerably reduced. However, when costs of added power procurement are included, antenna surface radiators would still cost a total of $6.78 billion for the LPS ($3,499 billion for waveguides and $3,323 billion for additional power-related expenditures). Excess power lost to inefficiencies in an open mesh LPS antenna would mainly be radiated onto the Earth environment. Mesh irregularities have an affect similar to random phase errors in diffusely spreading the main beam and elevating sidelobes. These environmental consequences could seriously limit the feasibility of an open mesh LPS antenna system, since maintenance of sidelobes below the .01 mW/cm guideline was one of the chief design constraints on the SPS microwave transmission system.
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