极化旋转域特征驱动的极化ISAR空间目标分类

Polarimetric ISAR Space Target Classification Driven by Polarimetric Rotation Domain Features

  • 摘要: 随着航空航天技术的发展,世界各大强国发射了大量遥感成像卫星、通信卫星等空间目标。地基极化逆合成孔径雷达(Inverse Synthetic Aperture Radar,ISAR)具有远距离、高分辨、全天时、全天候的工作特点,能够获取空间目标高分辨率二维雷达图像。基于极化ISAR图像开展空间目标分类识别对研判目标载荷类型和潜在行为意图具有重要意义。针对空间目标散射多样性带来的解译模糊问题和极化ISAR图像全局特性感知难题,本文立足极化ISAR体制,开展极化旋转域特征驱动的极化ISAR空间目标分类研究。首先,选取四型遥感成像卫星和通信卫星的计算机辅助设计(Computer Aided Design,CAD)模型开展电磁仿真,构造不同观测视角、不同带宽和不同信噪比参数的空间目标极化ISAR电磁仿真数据集;其次,针对空间目标散射多样性问题,将两通道之间的极化相关值扩展到绕雷达视线的极化旋转域,构造极化相关方向图解译工具,进而深入挖掘和提取极化相关方向图幅度类特征。同时,针对极化ISAR图像全局特性感知难题,优化现有深度学习模型,设计可提取极化ISAR图像全局特性的非局部注意力模型,进而深入挖掘极化ISAR图像非局部特征。最后,利用极化旋转域特征驱动嵌入了非局部注意力模型的深度学习网络,实现极化ISAR空间目标分类。基于不同观测视角、带宽和信噪比参数的空间目标电磁仿真数据开展实验验证,本文所提方法相较于现有方法具有更高的分类精度和鲁棒性。

     

    Abstract: ‍ ‍With advancements in aerospace technology, many military and technological powers globally have launched a vast number of space targets, including remote sensing imaging satellites and communication satellites, which significantly contribute to national defense and economic development. The ground-based polarimetric inverse synthetic aperture radar (ISAR) system is one of the primary means of observing these space targets, characterized by its ability to provide long-distance, high-resolution imaging in all weather conditions. The polarimetric ISAR system can generate high-resolution two-dimensional radar images of space targets. The classification and recognition of these targets based on polarimetric ISAR images are crucial for determining the type of payload and potential behavioral intentions of the targets. Recently, interpreting polarimetric ISAR images has become vital for classifying space targets. This paper addresses the challenges of interpretation ambiguity arisen from target scattering diversity and the sensing problem of polarimetric ISAR image global characteristics. We focus on the polarimetric ISAR system and conduct research on space target classification driven by polarimetric rotation domain features. First, we selected four types of satellites for our study: the HISEA-1 satellite, Starlink satellite, QPS-SAR satellite, and Capella satellite. We conducted electromagnetic simulations based on computer-aided design (CAD) models of the space targets using FKEO software to create a polarimetric ISAR electromagnetic simulation dataset. This dataset varied according to different observation angles, bandwidths, and signal-to-noise ratio parameters. Next, to tackle the issue of scattering diversity among space targets, we extended the polarimetric correlation values between two channels to the polarimetric rotation domain around the radar’s line of sight. We constructed a polarimetric correlation pattern tool to explore and extract the hidden information within this rotation domain. Various polarimetric correlation pattern features were derived, including polarimetric correlation original value, mean value, maximum value, minimum value, standard deviation value, contrast value, anti-entropy, beam-width, maximum angle, and minimum angle. We then selected the most recognizable amplitude polarimetric features for further analysis in polarimetric ISAR target classification. Additionally, to address the challenge of sensing global characteristics in polarimetric ISAR images, we optimized a popular deep learning model, ResNet. We developed a non-local attention mechanism that calculates the dependency relationship between any two points in the polarimetric ISAR images, allowing for the extraction of non-local features. Finally, we embedded this proposed non-local mechanism into the ResNet model after the convolutional layers, resulting in a new machine learning model called NL-ResNet. This model was driven by the selected polarimetric rotation domain features to achieve high-accuracy classification of polarimetric ISAR space targets. Experimental studies were conducted on the electromagnetic simulation data of the four types of space targets, varying in observation angles, bandwidths, and signal-to-noise ratio parameters. The proposed method demonstrated higher classification accuracy and robustness compared to other comparative methods.

     

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