A ground-based Nd:YAG laser operating at a wavelength of 1.06 ?mand emitting continuous output power of 6 kW produces a beam forlunar metrology that subtends a small solid angle2.51*10-6.
(a) What is its irradiance at the moon if the distance from earthis 310, 620 km?
(b) The beam also supplies power to explorers on the lunar surface.If a photovoltaic array that is 25% efficient at the laserwavelength is deployed, what area of the array is needed to supply10 W steadily?
(c) On its way to a lunar rendezvous from earth, a shiny spacecraftinadvertently passes through the beam at 9.5 km/s. What is thefrequency of the Doppler-shifted reflection observed back onearth?
(d) The laser is occasionally switched to pulsed mode to monitorthe earth-moon separation precisely using a corner-cube on thelunar surface. The return time of reflected light is measured witha fast detector that has more than enough temporal resolution toreproduce accurately the variation in time of signal intensity.What is the maximum square pulsewidth that can be used if theaccuracy of the measurement is to be better than ?d =
