基于VLBI站接收的火星探测器信号研究行星际闪烁

Interplanetary scintillation observation and analysis using Martian spacecraft downlink signal from VLBI station

利用VLBI单站对欧洲火星快车探测器(MEX)的太阳掩星过程进行观测,记录了太阳偏距(太阳中心到信号传播路径的垂直距离)在11 R⊙~160 R⊙范围内的MEX发射的X波段主载波信号,并通过VLBI宽带记录终端,提取了太阳风湍动导致的相位闪烁信息及相位闪烁功率谱,通过谱分析,测量了太阳风空间折射谱指数、折射结构常数与相位闪烁指数,探讨了利用相位闪烁指数反演沿视线方向的总电子含量(TEC)的可行性,分析表明,近太阳区域的相位闪烁显著强于远太阳区域;在3 mHz^0.3 Hz范围内,相位闪烁功率谱呈幂律分布,太阳风空间折射谱指数为-3.3±0.25,与Kolmogorov理论一致,且谱指数与太阳偏距无相关;表明在11 R⊙~160R⊙范围内,Kolmogorov理论可用于解释太阳风湍动及结构,太阳风折射结构常数与R近似满足~R^(-1.98±0.27)的关系,表明近太阳区域湍动强于远太阳区,利用相位闪烁指数获得的TEC与太阳活跃与平静期间模型计算值的变化趋势一致,试验表明,基于VLBI测站的多普勒测量及行星际闪烁研究可用于我国未来火星探测器的太阳掩星观测.

The Mars Express （MEX） passed through superior solar conjunction in June, 2015. The X-band telemetry signal of MEX with solar offset R in the range of 11 R-160 R were recorded by Sheshan VLBI station. Phase scintillation and its power spectral were extracted from VLBI broadband recording system. The phase scintillation spectral were power-low in the range of 3 mHz-0.3 Hz, and the corresponding refraction spectral index are kept constantly with -3.3±0.25 over the full range of solar offset from 11 R-160 R）, which is consistent with Kolmogorov turbulence. The structure constant of refractive index fluctuation has a relation of^R-1.98±0.27 with R, which indicates that the turbulence near solar is much stronger than that far from solar. The total electron content along the light sight_（TEC） through the solar wind was acquired with phase scintillation index. The change trend of TEC is consistent with the TEC calculated using models from both solar active and quiet periods. The Doppler measurement method and interplanetary scintillation based on VLBI station can be used in solar conjunction with Chinese Mars explorer in the future.