In the limiting case of a=l the power flux incident on the OSR should be less than 8042 watts/cm2 an order of magnitude greater than for solar cells. A plot of F* (for OSR's) versus a is in Fig. 3. 3.4 Damage to Mirrors Specific damage thresholds for metallic mirrors have been calculated elsewhere [16]. These assume variable absorptance and the theoretical values are compared with experimentally obtained values for irradiation with both 1.06 micron and 10.6 micron laser beams. These values are approximately one order of magnitude lower than those obtained for cover glasses of solar cells by the method outlined in this paper for the 1.06 um case. Normal optics in satellites use berryilium or special glasses as the base. Silver coatings on front and other surfaces provide the required optical characteristics. Anything that damages the optical quality of these coatings will significantly degrade performance. While most mirrors point towards the earth, various orbital configurations are possible in which these mirrors can be subjected to irradiation. For our calculations the melting of a layer 10 nanometres thick will be considered as sufficient for degrading performance.
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