HEW allows Class I laser doses of 0.0039 joules. It should be safe to look at the SPS transmitter image for: 3.9 x 10“3 j/3.357 x 10“7 Watts = 194 minutes Similarly, the whole SPS structure [albedo 1.0] reflecting sunlight to the eye would have a subtense of 46 sec. arc and could be viewed for 3.01 minutes. The SPS would mostly be photo cells [albedo = 0.05] allowing exposures of 60.2 minutes. A 1 Km. Solares mirror 4000 Km. high with 51.6 sec arc. subtense could be viewed for 2.40 minutes, minimum. Two factors reduce dose to the retina when viewing a point source. First, the eye's optics blur a point to a disk some 4 min. arc in radius, reducing peak intensity to 0.2% of the original [Figure 4, top]. Second,- involuntary eye movements during fixation move the image over a retinal region some 8 min. arc in radius. The eye wanders further from the fixation point with time; so that the longer one looks, the lower the peak dose for any one area. Figure 5 (top) shows that eye movements while fixating 1 minute wandered in an area one degree in diameter. At bottom is a magnified view of a 2 second portion of the top record, showing the eye moves in a series of small jerks, or saccades. Table 1 shows that motion reduces total dose half for 20 second exposures.
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