2014年NASA的DSN金星快车无线电掩星数据分析
Analysis of NASA's DSN Venus Express radio occultation data for year 2014
摘要：
金星快车无线电科学实验（Venus Express Radio Science Experiment，VeRa）是金星快车（Venus Express，VEX）航天器科学有效载荷的一部分，目的是调查金星的大气层、表面和重力场以及行星际介质。本文介绍了用于反演金星电离层和中性大气垂直剖面的VEX-VeRa原始无线电掩星数据的方法和所需的校准。在这项工作中，我们对2014年在NASA深空网络开环记录的一组25个VEX单频（X波段）掩星进行了独立分析。我们的温度，压力和电子密度的垂直分布与以前的研究在文献中。此外，我们的分析表明，金星的电离层受昼夜条件的影响比纬度变化更大，而中性大气则相反。我们对这些结果的科学解释是基于两个主要的影响：金星的高热惯性和纬向风。它们存在于金星的中性大气层中，这决定了为什么在这些地区，纬度依赖于白天/夜晚的条件。相反，在更高的高度，上述两种效应不太重要或为零，金星的电离层在探测的白天掩星中显示出更高的电子密度峰值，无论纬度如何。
英文摘要：
The Venus Express Radio Science Experiment (VeRa) was part of the scientific payload of the Venus Express (VEX) spacecraft and was targeted at the investigation of Venus' atmosphere, surface, and gravity field as well as the interplanetary medium. This paper describes the methods and the required calibrations applied to VEX-VeRa raw radio occultation data used to retrieve vertical profiles of Venus' ionosphere and neutral atmosphere. In this work we perform an independent analysis of a set of 25 VEX, single-frequency (X-band), occultations carried out in 2014, recorded in open-loop at the NASA Deep Space Network. Our temperature, pressure and electron density vertical profiles are in agreement with previous studies available in the literature. Furthermore, our analysis shows that Venus' ionosphere is more influenced by the day/night condition than the latitude variations, while the neutral atmosphere experiences the opposite. Our scientific interpretation of these results is based on two major responsible effects: Venus' high thermal inertia and the zonal winds. Their presence within Venus' neutral atmosphere determine why in these regions a latitude dependence is predominant on the day/night condition. On the contrary, at higher altitudes the two aforementioned effects are less important or null, and Venus' ionosphere shows higher electron density peaks in the probed day-time occultations, regardless of the latitude.
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