利用shearlet变换对探月雷达数据进行月壤结构的重建

Reconstruction of regolith structure from lunar penetrating radar channel 2 data based on shearlet transform

探月雷达作为嫦娥三号和嫦娥四号月球探测任务中最重要的科学载荷之一,其目标是探测月壤及地下结构信息.然而,嫦娥三号探月雷达的第二通道数据受到横向杂波的干扰,使得有用的反射信息被掩盖.这些杂波可以认为是影响数据质量的横向噪声,使得探月雷达数据信噪比低,影响数据解释.本文将利用shearlet变换对探月雷达数据进行信号分析与噪声去除,并对嫦娥三号着陆区的月壤结构进行重建.首先,在shearlet域中,观察横向噪声的分布,并分离出以噪声为主的shearlet分量,并得到重建后的雷达数据.随后,为充分利用嫦娥三号第二通道两套数据的整体优势,对两套经过shearlet变换去噪后的雷达数据进行融合,得到综合探月雷达图像,有效得去除了水平噪声并增强了来自浅月表的有效信号.最后,根据探月雷达处理结果对嫦娥三号着陆点的月壤结构进行重建,重建结构中的溅射物厚度与撞击坑溅射物经验公式结果得到了相互印证.

As a radar method for in-site detection,the Lunar Penetrating Radar(LPR)is onboard Chang′E-3(CE-3)and Chang′E-4(CE-4)for probing the structure of lunar regolith.Since the LPR Channel 2 data is muddled with a kind of horizontal clutter signal,we apply multi-scale geometric analysis(shearlet transform)in signal analysis and clutter signal attenuation for LPR Channel 2 data.Firstly,we observe the distribution of horizontal clutter signal in the shearlet domain and pick the noise-dominated sub-domain.Then we remove the local horizontal components in these sub-domain signals in shearlet domain.After removing the horizontal clutter signal,the interference by horizontal clutter signal is highlighted.The processed LPR Channel 2 data—as a new reference—aid geological stratification and interpretation.Finally,according to the LPR result,the geological stratification and interpretation of regolith on the CE-3 landing site is revealed,and the thickness of the ejecta in the reconstructed structure is consistent with the result of the empirical formula for crater ejecta.