SHARAD Signal Attenuation and Delay Offsets Due to the Martian Ionosphere
SHARAD Signal Attenuation and Delay Offsets Due to the Martian Ionosphere
复制标题
火星电离层造成的 SHARAD 信号衰减和延迟偏移
DOI：
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发表时间：
2014
影响因子：
4.8
通讯作者：
R. Phillips
中科院分区：
文献类型：
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作者：
B. Campbell;N. Putzig;F. Foss;R. Phillips
我们估计和纠正可变的时间延迟偏移之间的火星浅层雷达（SHARAD）探测观测的北极分层存款的火星在广泛的电离层条件。我们发现，这些延迟偏移线性相关的相位失真，这是由优化的表面和地下回波响应自动聚焦的幅度。我们使用这种关系来确定的相位参数和总电子含量（TEC）的火星电离层之间的经验缩放。该方法允许同时校正电离层引起的图像模糊和时间延迟误差，这些校正对于地下特征的3-D成像至关重要。我们还描述了SHARAD回波的衰减作为TEC的函数，以便于检测表面物理特性的季节性变化。在太阳耀斑事件期间，SHARAD信号经历相位失真和延迟，相对于典型的昼侧条件，TEC增加50%-100%，但衰减比预测的大10倍。增加的信号吸收可能是由于在中性粒子密度较高的较低海拔处增强的电子含量。
We estimate and correct variable time-delay offsets among Mars Shallow Radar (SHARAD) sounding observations of the north polar layered deposits of Mars under a broad range of ionospheric conditions. We find that these delay offsets are linearly related to the magnitude of the phase distortion, which is determined by optimization of the surface and subsurface echo response by autofocusing. We use this relationship to determine an empirical scaling between the phase parameter and the total electron content (TEC) of the Martian ionosphere. This method allows simultaneous correction of the image blurring and time-delay errors induced by the ionosphere, corrections that are crucial for 3-D imaging of subsurface features. We also characterize the attenuation of SHARAD echoes as a function of TEC to facilitate detection of seasonal changes in surface physical properties. During solar flare events, SHARAD signals experience phase distortion and delay consistent with a 50%-100% increase in TEC relative to typical dayside conditions, but up to tenfold greater attenuation than predicted. The increased signal absorption is likely due to enhanced electron content at lower altitudes where the neutral particle density is higher.