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首页> 外文期刊>Proceedings of the IEEE >The SHAllow RADar (SHARAD) Onboard the NASA MRO Mission
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The SHAllow RADar (SHARAD) Onboard the NASA MRO Mission

机译：美国国家航空航天局MRO任务中的SHAllow雷达（SHARAD）

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This paper describes the mission concepts, design, and achievements of the Italian Space Agency (ASI)-provided Mars SHAllow RADar (SHARAD) sounder high-frequency (HF) sounding radar, used onboard the National Aeronautics and Space Administration (NASA) Mars Reconnaissance Orbiter (MRO) Spacecraft. Its goals are the detection of liquid or solid water below the surface, and the mapping of subsurface geologic structures. Following a brief overview of the MRO mission and of its main science objectives, the paper introduces the basic principles of operation of the radar sounder, and addresses the major design issues faced by such a system. The greatest challenges faced in the design are the control of the interference from off-nadir echoes and the need for a high signal fidelity over a very large fractional bandwidth. The core of the paper is devoted to describing how the above problems have been tackled in the design of the SHARAD instrument, and the main characteristics of its architecture. The two key features of the instrument system design are 1) generation of the transmitted signal directly at the transmitted frequency; and 2) sampling performed directly at the radio frequency (by means of a subsampling technique). The careful design of these features, intended to keep the analog signal path very simple, minimizes distortions and stability problems. An overview of the calibration approach of both the system impulse response and the antenna gain at nadir versus solar array position, an assessment of the in-flight performance of the instrument, and a short summary of the achieved science results are also provided.
机译：本文介绍了由意大利航天局（ASI）提供的火星SHAllow雷达（SHARAD）测深仪高频（HF）测深雷达的任务概念，设计和成就，该雷达用于美国国家航空航天局（NASA）火星侦察轨道飞行器（MRO）航天器。它的目标是检测地表以下的液态或固态水，以及绘制地下地质构造图。在对MRO任务及其主要科学目标进行简要概述之后，本文介绍了雷达测深仪的基本操作原理，并解决了该系统面临的主要设计问题。设计面临的最大挑战是控制离天底回波的干扰以及在很大的小部分带宽上需要高信号保真度的需求。本文的核心致力于描述SHARAD仪器设计中如何解决上述问题以及其架构的主要特征。仪器系统设计的两个关键特征是：1）直接以发射频率产生发射信号； 2）直接在射频上进行采样（通过子采样技术）。这些功能的精心设计旨在使模拟信号路径保持非常简单，从而最大程度地减少了失真和稳定性问题。还概述了系统脉冲响应和天底对太阳能阵列位置的天线增益的校准方法，评估了仪器的飞行性能，并简要概述了所获得的科学结果。

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