Shallow aquifers are the largest freshwater bodies in the North African Sahara and the Arabian Peninsula. Their groundwater dynamics and response to climatic variability and anthropogenic discharge remain largely unquantified due to the absence of large-scale monitoring methods. Currently, the assessment of groundwater dynamics in these aquifer systems is made primarily from sporadic well logs that barely cover a few percent of the geographical extent of these water bodies. To address this deficiency, we develop the use of an ultra-wideband (UWB) very high frequency (VHF) interferometric airborne sounding radar, under a collaboration between NASA and the Qatar Foundation, to characterize the depth and geometry of the shallowest water table in large hyperarid hydrological basins in North Africa and the Arabian Peninsula. Herein, we describe the science objectives, measurement requirements, instrument design, expected performance, flight implementation scenarios, primary targets for investigation, and the first technology demonstration of the concept. Our performance analyses suggest that an airborne, nadir-looking sounding radar system operating at a 70-MHz center frequency with a linearly polarized folded-dipole antenna array—enabling a bandwidth (BW) of 50 MHz—and a surface signal-to-noise ratio (SNR) of 85 dB flying at an altitude of 500–2,000 m can map the uppermost water table depths of aquifer systems spanning tens of kilometers at a vertical resolution of 3 m in desiccated terrains to an average penetration depth of 50 m, with a spatial resolution of 200 m. For the first time, this airborne concept will allow time-coherent high-resolution mapping of the uppermost water tables of major aquifer systems in hyperarid areas, providing unique insights into their dynamics and responses to increasing climatic and anthropogenic stressors, which remain largely uncharacterized. The aforementioned significantly surpasses the existing capabilities for mapping shallow aquifers in these harsh and remote environments, which relies today on data collected on different timescales from sparse well logs that do not cover their geographic extents. A list of key abbreviations for this article can be found in “The Key Abbreviations Used in This Article.”

中文翻译：

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用于沙漠地下含水层勘探的机载探测雷达：沙漠-海洋：任务概念研究 [航天机构]

浅层含水层是北非撒哈拉和阿拉伯半岛最大的淡水水体。由于缺乏大规模监测方法，其地下水动态以及对气候变化和人为排放的响应在很大程度上仍然无法量化。目前，对这些含水层系统地下水动态的评估主要是根据零星的测井数据进行的，这些测井数据几乎只覆盖了这些水体地理范围的百分之几。为了解决这一缺陷，在 NASA 和卡塔尔基金会的合作下，我们开发了使用超宽带 (UWB) 甚高频 (VHF) 干涉机载探空雷达来表征最浅地下水位的深度和几何形状。北非和阿拉伯半岛的大型极度干旱水文盆地。在此，我们描述了科学目标、测量要求、仪器设计、预期性能、飞行实施场景、主要研究目标以及该概念的首次技术演示。我们的性能分析表明，机载、天底探测探测雷达系统在 70 MHz 中心频率下运行，具有线性极化折叠偶极子天线阵列（可实现 50 MHz 的带宽 (BW)）和表面信噪比在500-2,000 m的高度飞行时，信噪比（SNR）为85 dB，可以在干燥地形中以3 m的垂直分辨率绘制跨越数十公里的含水层系统的最高地下水位深度，平均穿透深度为50 m，空间分辨率为200 m。这种机载概念将首次实现对极度干旱地区主要含水层系统最上层地下水位进行时间相干高分辨率测绘，从而提供关于其动态以及对不断增加的气候和人为压力源的响应的独特见解，而这些压力源在很大程度上仍然是未知的。上述功能显着超越了在这些恶劣和偏远环境中绘制浅层含水层的现有能力，这些能力目前依赖于从不覆盖其地理范围的稀疏测井中在不同时间尺度上收集的数据。本文的关键缩写列表可以在“本文中使用的关键缩写”中找到。