CASE SI: OTV IN LEO - CONSTRUCTION PHASE This case is similar to Case DI (Geometry in Figure 24) except the specular Equation (2) is now used. It was found that considerable light can be reflected to the earth over a number of daylight hours, so that the general case will be treated. The geometry is illustrated in Figure 25. The angle between the reflected beam R and the orbital plane is 53.5° (see Figure 22). The distance from the OTV in LEO to the illuminated spot on the ground is where $ is the angle from the moon meridian. The value of R for the noontime case (<t> = 0°) is 910 km. Note that the reflected light just grazes the earth at (J) = 50.9°. Thus an illuminated spot moves across the day side of the earth from 0830 to 1530 local time. In Figure 26, R is plotted as a function of <J> and the irradiance (Equation (1)) as a function of R for the following conditions: For these parameters, the peak irradiance at the ground for the front side is 2 2 1.2 W/nr while that for the back side is 19 W/m . Not only would it be difficult to make the OTV optically flat, but it would be clearly disadvantageous if it were flat. It is estimated that misalignment of the OTV solar panels yields a beam spread of 1.5° compared with the 0.5° spread of the sun's disk produced by a flat mirror. Then the factor a /(p + a + t) in Equation (2) reduces the irradiance by about an order of magnitude. Besides avoiding flat surfaces, other methods of reducing the
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