The Mars Curiosity rover carries an instrument, ChemCam, designed to measure the composition of surface rocks and soil using laser-induced breakdown spectroscopy (LIBS). The measured spectra from this instrument must be analyzed to identify the component elements in the target sample, as well as their relative proportions. This process, which we call disaggregation, is complicated by so-called matrix effects, which describe nonlinear changes in the relative heights of emission lines as an unknown function of composition due to atomic interactions within the LIBS plasma. In this work, we explore the use of the plasma physics code ATOMIC, developed at Los Alamos National Laboratory, for the disaggregation task. ATOMIC has recently been used to model LIBS spectra and can robustly reproduce matrix effects from first principles. The ability of ATOMIC to predict LIBS spectra presents an exciting opportunity to perform disaggregation in a manner not yet tried in the LIBS community, namely via Bayesian model calibration. However, using it directly to solve our inverse problem is computationally intractable due to the large parameter space and the computation time required to produce a single output. Therefore, we also explore the use of emulators as a fast solution for this analysis. We discuss a proof of concept Gaussian process emulator for disaggregating two-element compounds of sodium and copper. The training and test datasets were simulated with ATOMIC using a Latin hypercube design. After testing the performance of the emulator, we successfully recover the composition of 25 test spectra with Bayesian model calibration.

中文翻译：

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用于估计火星岩石和土壤成分的贝叶斯模型校准的初步探索

好奇号火星车携带了一种名为 ChemCam 的仪器，旨在使用激光诱导击穿光谱 (LIBS) 测量地表岩石和土壤的成分。必须分析来自该仪器的测量光谱，以识别目标样品中的组成元素及其相对比例。我们称之为分解的这个过程因所谓的基质效应而变得复杂，基质效应将发射线相对高度的非线性变化描述为由于 LIBS 等离子体内原子相互作用引起的未知成分函数。在这项工作中，我们探索了在洛斯阿拉莫斯国家实验室开发的等离子体物理代码 ATOMIC 的使用，用于分解任务。ATOMIC 最近被用来模拟 LIBS 光谱，并且可以根据第一原理稳健地再现基质效应。ATOMIC 预测 LIBS 光谱的能力提供了一个令人兴奋的机会，可以以 LIBS 社区尚未尝试的方式进行分解，即通过贝叶斯模型校准。然而，由于大的参数空间和产生单个输出所需的计算时间，直接使用它来解决我们的逆问题在计算上是难以处理的。因此，我们还探索了使用模拟器作为此分析的快速解决方案。我们讨论了用于分解钠和铜的二元化合物的高斯过程仿真器的概念验证。使用拉丁超立方体设计，使用 ATOMIC 模拟训练和测试数据集。在测试了模拟器的性能后，我们通过贝叶斯模型校准成功地恢复了 25 个测试光谱的组成。