Fig. 9. Receptor site protection radius as a function of the perimeter power-density SPS, angular beam deflection caused by gross platform motion will occur on a time scale much slower than the laser system response time. The most plausible accident corresponds to complete loss of laser-transmitter phase control. The highly improbable, but worst-case situation, thus involves a slew in the optical pointing vector by about 1.6 x 10 6 rad, representing a maximum shift in the primary mirror phase of 4 wavelengths before laser shutdown. Under these circumstances, all or part of the beam will slew away from the receptor by about 70 m before power-off conditions are achieved. Hence, large slew distances of the focused beam are not possible. Because of the laser’s damage potential to biological entities (49), it is imperative that adequate safeguards and security exist to prevent sabotage or hostile control. These safeguards would normally take the form of failsafe criteria and automated power-up/power-down sequences. Weapon-quality beams (>1 kW/cm-), however, are not possible within the atmosphere for the present system. A small percentage of laser power spillover (£1%) will be unavoidable at the receptor device. Hazards to operating personnel and innocent bystanders exist due to possible specular or diffuse reflections from the spillover region adjacent to the receptor device. Operating personnel will be required to wear protective goggles and clothing when working in this region. An opaque perimeter fence, of appropriate height, will be placed at the boundary where the time-average power density equals the maximum recommended continuous exposure levels for humans. The American National Standards Institute (ANSI) exposure limit for cw infrared lasers is 100 mW/cm2. This limit was determined for relatively small spot sizes on the skin or eye based on durations in excess of 10 sec. For large-area, long-duration exposure, Sliney et al. (50) recommend an average ocular or wholebody irradiance limited to about 10 mW/cm2. The protection radius as a function of perimeter power density is shown in Figure 9 for the uniform-intensity and Gaussian laser beam distributions. If a maximum
RkJQdWJsaXNoZXIy MTU5NjU0Mg==