Probability of Hazardous Human Exposure from Space Based Lasers

Laser (lidars) used from satellites and space stations for measurement of atmospheric properties may represent an ocular hazard to people on the surface of the earth. The risk of an eye injury depends on a range of parameters such as the energy per pulse, wavelength, beam divergence, space craft orbit, atmospheric conditions, properties of telescopes and other viewing aids, and the viewing behaviour of potentially exposed people. The probability of receiving an eye injury is a combination of the probability of being exposed and the probability of the incident energy levels of raditiaon producing eye injury. Some aspects of this later probability are discussed in another paper presented at this conference (1). Here we discuss a concept of an overall risk assessment as applicable to satellite based lasers, and the probabiltiy that ocular exposure to the laser radiation occurs. The probability of sustaining eye damage varies with laser parametes and satellite path and, across the globe, with population density and social habits. For the typical satellite based lidar, the probability of an individual being exposed to the beam, and the probability of sustaining eye damage, are both very small and may in some cases be zero.