New Venus Atmospheric Exploration Using Magelan S-band Radio Tracking Wave

本文提出并分析了一种测量金星近地表低层大气(35公里)的射电科学新技术。为了克服普通射电测量技术测量金星表面附近大气密度高的困难，利用了轨道航天器向金星表面发射的反射波。测量了金星表面反射波与金星轨道航天器直接传输到地球上的反射波的光程差。通过改变反射波的入射角度，可以得到折射率随高度的变化关系。密度分布可以由折射率得到。在分析过程中发现，尽管金星表面附近的大气密度很高，但折射率的偏差仍然很小，因此只有当大气相对于水平面的入射角较小时才能得到大气结构。密度分布的水平变化可以通过航天器运动获得。不幸的是，NASA金星航天器Megelan在这项研究的早期阶段终止了任务，现在无法用航天器测试这一想法。Magelan获得的高度信息对这项新的射电科学技术非常重要。还对参与下一次金星探测“金星多探测器任务”的情况进行了调查。

A new radio science technique to measure the Venus lower atmosphere (<35km) near the surface is proposed and analyzed. In order to overcome the difficulty of the ordinary radio accultation technique to measure the Venus atmosphere near its surface due to the high density of the atmosphere near the Venus surface, the reflection wave transmitted from an orbiting spacecraft towards the Venus surface is utilized. The light path difference of the reflected wave on the Venus surface and the one directly transmitted to the earth from the Venus orbiting spacecraft is measured. By changing the injection angle of the reflected wave, the altitude dependence of the refractive index can be obtained. The density profile can be obtained from the refractive index. In the course of the analysis, it is revealed that, though the atmospheric density is very high near the Venus surface, the deviation of the refractive index is still small so that the atmospheric structure can only be obtained when the injection angle to the atmosphere with respect to the horizontal plane should be small. The horizontal variation of the density profile can be obtained by the spacecraft motion.Unfortunately, the NASA Venus spacecraft Megelan terminated its mission in the early phase of this research, and it was now impossible to test this idea using the spacecraft. The altitude information obtained by Magelan is very important for this new radio science technique. The participation in the next Venus exploration "Venus Multiprobe Mission " is also investigated.