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Near-optimal inversion of incoherent scatter radar measurements: coding schemes, processing techniques, and experiments

机译：非相干散射雷达测量的近似最优反演：编码方案，处理技术和实验

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摘要

Accurate and efficient estimation of the key ionospheric state parameters such as electron density, ion composition, and electron and ion temperatures is required to understand fundamental issues of terrestrial plasma physics such as redistribution of energy and momentum, and coupling within terrestrial upper atmosphere regions. This work focuses on developing a modern coding scheme and inversion methodology using Arecibo incoherent scatter radar (ISR) to achieve efficient, and near-optimal estimates of the key ionospheric parameters. In particular, this work considers two aspects of the ISR inversion problem: (i) ISR lag estimates at individual altitudes, and (ii) modulation techniques that can provide more accurate estimates with a specific range resolution. These two aspects suggest a unifying framework for ISR inversion in which modern computational technology and ISR methodology are utilized in a robust estimation procedure.The first contribution of this work is the development of a discrete forward model for F-region incoherent scatter measurements, where long pulses are utilized in transmission. The range smearing imposed on measurements by long pulses is modeled as a one-dimensional convolution along the range in the simplified case where the receiver sampling is instantaneous. The next major phase of this research is to develop an efficient hybrid technique that allows for estimation of plasma parameters by removing range smearing from measurements. The inversion technique incorporates both quadratic and edge-preserving regularization approaches in order to provide smooth plasma auto-correlation function (ACF) lag profiles in the presence of noise while still resolving the sharp gradients.Another contribution of this thesis is to develop a technique for optimal modulation design in ISR experiments. The optimal resolution supported by ISR measurements is used as one criterion for the optimal design. The model order selection framework is applied to the problem at hand to find the optimal resolution. The results indicate that, compared with a long pulse, amplitude-modulated codes yield finer range resolutions with nearly similar parameter estimation errors or smaller estimation errors with the same range resolution. In medium to high SNR scenarios, a smaller on-off ratio of the transmitted waveform is recognized as a determining factor for allowing more freedom in removing range ambiguities as well as resulting in improved statistical accuracy for integrated data in range and lag directions. In order to find the optimal amplitude modulation for Arecibo ISR measurements in medium to high SNR scenarios, a modified form of the sequential backward selection algorithm is applied to the space of all amplitude modulated pulses with a certain on-off ratio. Due to the vast search space, there is no possibility for an exhaustive search. Therefore, the problem of finding the optimal amplitude modulation is viewed as an optimization problem. Three optimality criteria, namely, sum of squared errors, uniformity of estimation errors, and condition number of convolution matrices, are considered.The final contribution of this work was implementing and conducting several experiments in April 2004, August 2005, and July 2006 using the incoherent scatter radar at Arecibo Observatory, and applying the inversion technique to estimate the plasma parameters. In these experiments, the original mode of MRACF was modified to utilize amplitude modulation. The results of all these experiments verify that when the SNR is sufficiently high, compared with an unmodulated long pulse, improved range resolution with nearly the same statistical accuracy is obtained when an amplitude modulationis utilized.The results of the developed methodology and experimental design of this work can be extended to other incoherent scatter radars (such as Jicamarca radar in Peru, and advanced modular incoherent scatter radar in Alaska) to improve the estimation task in other altitude and latitude regions, and to extract many further ionospheric parameters such as electric field strength, conductivity, current, and neutral wind speed.
机译：需要准确有效地估算关键电离层状态参数（例如电子密度，离子组成以及电子和离子温度），以了解地面等离子体物理的基本问题，例如能量和动量的重新分布以及在地面高层大气区域内的耦合。这项工作着重于开发使用Arecibo非相干散射雷达（ISR）的现代编码方案和反演方法，以实现对关键电离层参数的高效且接近最佳的估计。特别是，这项工作考虑了ISR反演问题的两个方面：（i）在各个高度上的ISR滞后估计，以及（ii）可以提供具有特定范围分辨率的更准确估计的调制技术。这两个方面为ISR反演提供了一个统一的框架，在该框架中，现代计算技术和ISR方法被用于鲁棒的估计程序中。这项工作的第一贡献是开发了用于F区非相干散射测量的离散前向模型，其中脉冲用于传输。在接收器采样是瞬时的简化情况下，将长脉冲施加在测量上的距离拖尾建模为沿该距离的一维卷积。这项研究的下一个主要阶段是开发一种有效的混合技术，该技术可通过消除测量中的距离拖尾来估算血浆参数。为了在噪声存在的情况下提供平滑的等离子体自相关函数（ACF）滞后曲线，同时又解决了陡峭的梯度，该反演技术结合了二次方和边缘保留正则化方法。 ISR实验中的最佳调制设计。 ISR测量支持的最佳分辨率用作最佳设计的标准之一。将模型顺序选择框架应用于当前问题以找到最佳解决方案。结果表明，与长脉冲相比，幅度调制码产生的细微距离分辨率具有几乎相似的参数估计误差，或者具有相同的距离分辨率较小的估计误差。在中到高SNR场景中，较小的发射波形开/关比被认为是决定因素，以允许更大的自由度消除范围模糊度，并提高范围和滞后方向上的集成数据的统计准确性。为了在中等到高SNR情况下找到用于Arecibo ISR测量的最佳幅度调制，对所有具有一定通断比的幅度调制脉冲的空间应用一种改进形式的顺序后向选择算法。由于搜索空间巨大，因此不可能进行详尽的搜索。因此，找到最佳幅度调制的问题被视为优化问题。考虑了三个最优标准，即平方误差之和，估计误差的均匀性以及卷积矩阵的条件数。这项工作的最终贡献是在2004年4月，2005年8月和2006年7月使用阿雷西博天文台的非相干散射雷达，并应用反演技术估算等离子体参数。在这些实验中，修改了MRACF的原始模式以利用幅度调制。所有这些实验的结果证明，与未调制的长脉冲相比，当SNR足够高时，使用幅度调制时可以获得改进的范围分辨率，并且具有几乎相同的统计精度。该方法的开发方法和实验设计的结果可以将工作扩展到其他非相干散射雷达（例如秘鲁的Jicamarca雷达和阿拉斯加的先进模块化非相干散射雷达），以改善其他海拔和纬度地区的估算任务，并提取许多其他电离层参数，例如电场强度，电导率，电流和中性风速。

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    Nikoukar Romina;

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  • 年度 2010
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  • 正文语种 {"code":"en","name":"English","id":9}
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