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ORION: clearing near-Earth space debris in two years using a 30-kW repetitively-pulsed laser

Nearly 200,000 pieces of debris in the 1 - 20 cm range in low- Earth orbit (LEO), a legacy of 35 years of spaceflight now threaten long-term space missions. An economical solution to the problem is to use a ground-based laser to create a photoablation jet on the objects and cause them to re-enter the atmosphere and burn up. A sensitive optical detector is required to locate objects as small as 1 cm at 1500 km range. Applied when the object is rising and between about 45 and 15- degree zenith angle, the necessary (Delta) v is of order 100 m/s. A laser of 30 kW average power at 5-ns pulsewidth and a 4 - 6 m mirror with adaptive optics can clear near-Earth space of the 1-20-cm debris in 2 years of operation. A high altitude site minimizes turbulence correction, interference from nonlinear optical effects, and absorption. We discuss the effect of nonlinear optical processes in the atmosphere as boundaries on propagation, and how to choose system parameters to guarantee optimum conversion of laser energy to target momentum. The laser might be Nd:glass (1.06 micrometer/530 nm), or iodine (1.3 micrometer).