Study of simultaneous multiple target shot technique for space debris mitigation

提出了一种利用高功率星载激光减缓空间碎片的方案。该计划针对的是以前从未处理过的所谓小碎片。该方案采用光学相位共轭技术，利用单个光学系统对目标进行捕获、跟踪和瞄准。研究了布里渊增强四波混频作为一种位相共轭技术的基本特性，计算了瞬时撞击时空间碎片被推向大气层上层的初始碰撞。利用激光能量转化为激光烧蚀动量的效率--动量耦合系数，计算了所需激光能量。因此，据估计，激光脉冲能量对碎片造成足够大的轨道偏转是必要的。计算了距离、侵入时间和偏转能量，设计了激光系统需要产生的平均功率。然后研究了激光光束的波前控制，研究了利用相位共轭进行碎片捕获、跟踪和瞄准的可行性。对各种像差引起的波前失真的补偿程度。测试的像差源包括透镜、柱面透镜、随机位相板。对于所有的像差，已经确认了大约90%的保真度。碳氟化物(FG72)是一种环境友好的材料，作为一种非线性光学介质进行了测试。测试了该材料在保持有效全息光栅时的时间响应，发现该材料的时间响应高达100 MHz。为了实现基于位相共轭技术的碎片减缓系统，提出了一种配备带有同心衍射光栅的凸次镜的多功能望远镜。

A scheme of space debris mitigation using high-power space-born laser has been proposed. The scheme targets so called small debris that has not been treated before. The scheme uses optical phase conjugation for target acquisition, tracking and targeting with a single optical system. Basic characteristics of Brillouin enhanced four wave mixing as a phase conjugation technique was studied.An initial impact has been calculated to push space debris into the upper atmospheric layer when instantaneous impact is exerted. Required laser energy was also calculated using momentum coupling coefficient, an efficiency of laser energy conversion to momentum of laser ablation. Thus laser pulse energies were estimated necessary to cause large enough orbital deflection to debris. Distance, time of trespassing and energy of deflection were also calculated so that average power that the laser system has to generate can be designed.Wave front control of laser beam then investigated to study the feasibility of the use of phase conjugation for debris acquisition, tracking and targeting. A degree of compensation of wave front distortion caused by various aberrations. The source of aberrations tested include lens, cylindrical lens, random phase plate. For all the aberrations, about 90 % fidelity has been confirmed.Carbon Fluorinert (FG72) that is environmentally safe material was tested as a nonlinear optical medium. Temporal response of the material in terms of holding efficient holographic grating was tested and found to be as high as 100 MHz.In order to realize a debris mitigation system using the phase conjugation technique, multi functional telescope equipped with a convex secondary mirror with concentric diffraction grating was proposed.