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On 15 February 2013, a previously unknown ~20 m asteroid struck Earth near Chelyabinsk, Russia, releasing kinetic energy equivalent to ~570 kt TNT. Detecting objects like the Chelyabinsk impactor that are orbiting near Earth is a difficult task, in part because such objects spend much of their own orbits in the direction of the Sun when viewed from Earth. Efforts aimed at protecting Earth from future impacts will rely heavily on continued discovery. Ground-based optical observatory networks and Earth-orbiting spacecraft with infrared sensors have dramatically increased the pace of discovery. Still, less than 5% of near-Earth objects (NEOs) ≥100 m/~100 Mt TNT have been identified, and the proportion of known objects decreases rapidly for smaller sizes. Low emissivity of some objects also makes detection by passive sensors difficult. A proposed orbiting laser phased array directed energy system could be used for active illumination of NEOs, enhancing discovery particularly for smaller and lower emissivity objects. Laser fiber amplifiers emit very narrow-band energy, simplifying detection. Results of simulated illumination scenarios are presented based on an orbiting emitter array with specified characteristics. Simulations indicate that return signals from small and low emissivity objects is strong enough to detect. The possibility for both directed and full sky blind surveys is discussed, and the resulting diameter and mass limits for objects in different observational scenarios. The ability to determine both position and speed of detected objects is also discussed.

Directed energy active illumination for near-Earth object detection