Adaptive Optical Systems in Air-Based Laser System. Analytical Review. Part 1. Current Status

Aviation-based laser complex is a complex technical object. Among its systems, we analyse only an adaptive optical system and issues related to its performance, and show that the effectiveness of the complex without an adaptive system is small. The analysis was carried out in terms of systems that were developed in the United States. Using the tilt corrector, an adaptive optics provides accurate tracking of the object. A deformable mirror performs correction of higher-order radiation wavefront aberrations caused by atmospheric turbulence for incoming light and outgoing laser radiation. The advantages of onboard laser systems are the beam propagation at the speed of light and the low price of a shot. The disadvantages are that the target should be in line-of-sight and there is a negative influence of the atmosphere. Another negative influences are vibrations of the aircraft and the aero-optical problem because of output radiation. An assured thermal target kill is possible at the range of 3-10 km. A functional kill and suppression are capable at ranges of 10 2 -10 3 times longer than for the thermal target kill. Among the programs for the development of an onboard laser in the USA, the YAL, ATL and ABL programs are considered. The YAL program is an attempt to intercept short-and medium-range missiles with a powerful laser. The ATL system was to be installed on a heavily armed ground support aircraft. An airborne laser (ABL) is a demonstration of the U.S. Air Force of a high-energy laser system designed to destroy missiles on their boost phase. Over 30 years and several tens of billions of dollars were expended to develop the systems. Unfortunately, all onboard laser development programs have been closed. Experience of the flying laboratories is realized by Cessna Citations and Falcon 10s planes and is relevant, as it gives the chance to estimate adverse effects of aero-optics and vibrations directly in flight. Among the problems that need to be solved when creating adaptive optics for an onboard laser, the following are highlighted: - loss of compensation capabilities; - thermal effects of laser radiation on optical elements; - creation of attenuators and radiation couplers; -    mitigating the negative effects of the onboard platform on radiation; - operation reliability of the actuators of correction devices; - technological working off of the uncooled optical elements which are affected by powerful laser radiation. For newly developed aviation-based laser systems, it is necessary to envision the niche in which their use will be most efficient.