星载海洋激光雷达最佳工作波长分析

Analysis of the optimal operating wavelength of spaceborne oceanic lidar

星载激光雷达是实现海洋垂直剖面探测的有效工具,也是目前迫切需求的海洋光学遥感手段。对星载海洋激光雷达的波长参数进行评估对保证探测有效性具有重要意义。本文从探测深度和信噪比两方面分析了星载海洋激光雷达探测全球海洋的最佳波长。利用MODIS 10个波段的水体光学特性数据,估算全球海水探测深度及相应的最优波长;并根据太阳夫琅禾费暗线特性,对信号信噪比进行优化。结果表明:在探测深度方面,最优探测波长在488 nm波段的海洋占全球海洋面积的70%左右,并且全球95%以上的海域在488 nm波段的探测深度优于0.8倍的真光层深度;在信噪比方面,相对于488 nm波段,486.134 nm夫琅禾费暗线处采用0.1 nm带宽的滤光片可以将背景光强度降低70%,相应地回波信噪比整体提升了约5.0%。就全球海洋探测来说,使用486.134 nm作为探测波长可以提高探测深度,有效抑制太阳背景光,提高信噪比,因此,486.134 nm是星载海洋激光雷达的最佳工作波长。

Spaceborne lidar is a promising tool for vertical ocean profile detection,which has attracted extensive attention in oceanic optical remote sensing technology.It is essential to evaluate the operating wavelength of spaceborne oceanic lidar to ensure that it is effective.In this paper,the optimal operating wavelength of spaceborne oceanic lidar for the purposes of global ocean detection was analyzed in terms of detection depth and signal-to-noise ratio(SNR).The global distribution of ocean detection depths and the corresponding wavelengths were estimated by using the oceanic optical properties data from MODIS.The SNR was evaluated based on the characteristics of the solar Fraunhofer line.It was found that ocean water with an optimal wavelength of 488 nm accounts for about 70%of the global ocean area and more than 95%of the global ocean area has a detected depth deeper than 0.8 times the depth of the euphotic layer.Furthermore,70%of background light can be suppressed with a filter against the 0.1 nm bandwidth at the 486.134 nm solar Fraunhofer line and the SNR can be increased by about 5.0%compared to that of the 488 nm.In conclusion,working at 486.134 nm can effectively improve the detection depth and the SNR,so it is the optimal operating wavelength of spaceborne oceanic lidar.