基于1.06 μm波长的空间合作目标及碎片高精度激光测距试验

1.06 μm wavelength based high accuracy satellite laser ranging and space debris detection

常规卫星激光测距大多数采用532 nm波长激光,但受激光能量和大气透过率低等瓶颈制约,在微弱目标探测如碎片激光测距、月球激光测距中使用难度较大.本文介绍了基于1.06μm波长的激光测距技术,分析了1.06μm测距技术在激光能量、大气传输、背景噪声、单光子探测等方面相对于532 nm激光测距的优势,分析了其应用于微弱目标激光测距的前景,提出了针对1.06μm激光测距系统的改造方案,在上海天文台532 nm卫星激光测距系统的基础上,完成了系统改造,国内首次利用1.06μm增强的In Ga As探测器实现对合作目标的高精度厘米级激光测距,证明了1.06μm波长激光测距技术在系统噪声和测量效率等方面的优势,并且实现了该波长对1500 km空间碎片目标的高精度激光测距,为未来远距离微弱目标高精度近红外波段激光测距提供了紧凑、低成本、易操作的测量技术方案.

Classical satellite laser ranging(SLR)technology based on 532 nm wavelength usually adopts low energy laser to measure cooperative objects.However,for a very weak target,such as debris and lunar reflector arrays,laser ranging system should have much stronger detection capability than the laser ranging system for traditional application.A common way to improve system detection capability is to use high energy laser.With an additional frequency doubling crystal,it is more difficult to make a high energy laser based on 532 nm than that based on 1.06μm,which restricts the improvement of system detection capability,and also gives rise to the short lifetime,poor system stability problems.Compared with 532 nm laser,the 1.06μm laser has many advantages of high laser energy and power,high atmospheric transmissivity,and low background noise,thereby making it an ideal substitution for the traditional 532 nm SLR system.In this paper,we comparatively analyze the above-mentiond advantages of the 1.06μm laser and other system’s key parameters such as detector efficiency and target reflection efficiency,calculate the echo photons one can obtain,and establish a 1.06μm laser ranging system based on the existing 532 nm SLR at Shanghai Astronomical Observatory.Owing to the using of an InGaAs single photon detector,the system turns very compact,low cost,easy-to-be-installed and has almost no additional operation complexity than the 532 nm system.With this system,the high precision1.06μm laser ranging for cooperative objects based on InGaAs detector is carried out for the first time in China,and a ranging for space debris 1500 km away can also be realized.The ranging experiment shows with the same laser,SLR using 1.06μm output reaches a detection efficiency of 7 times the detection efficiency the SLR using 532 nm output reaches,and the background noise only 1/5.This approves the advantages and feasibility of 1.06μm system,and also shows its great potential application prospects in the high precision weak target laser detection in the day and night time.This paper provides a very easy operation,high compact and low cost method for the future high precision weak target laser ranging.