N. M. M. Said, G. Molera Calvés, P. Kummamuru, J. Edwards, M. Maoli, G. Cimo’
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引用次数: 0
Abstract
Ground-based observations of spacecraft signals have been used to study space weather. However, single spacecraft measurements observed from the Earth have limitations in studying the structure and evolution of solar plasma as they are unable to differentiate spatial and temporal variations. To overcome this limitation and improve our understanding of interplanetary scintillation, we simultaneously observed radio signals transmitted by two co-orbiting spacecraft: the ESA Mars Express (MEX) and the Chinese National Space Administration Tianwen-1 (TIW-1). We conducted the observations from April to November 2021 using the University of Tasmania’s VLBI radio telescopes at 8.4 GHz. We employed the Planetary Radio Interferometer and Doppler Experiment (PRIDE) technique to determine the topocentric Doppler measurements and residual phase of the carrier signal. These observables were used to quantify the phase fluctuations of the spacecraft signals caused by solar wind and hydrodynamic turbulence in the interplanetary medium. The measured phase fluctuations RMS from both spacecraft show small differences which are caused by factors such as the spacecraft’s motion, onboard electronics, and variations in the uplink signal path through Earth’s ionosphere. These fluctuations decrease with solar elongation and correlate with solar radio flux at 10.7 cm (2800 MHz), indicating solar activity. The estimated total electron contents along MEX and TIW-1’s radio lines of sight are similar, with higher values at lower solar elongations. Simultaneous multi-spacecraft observations also enable RFI characterization, frequent spacecraft performance comparisons, and investigation of solar activity effects on spacecraft performance and scientific outcomes.
对航天器信号的地面观测已被用于研究空间天气。然而,从地球上观测到的单航天器测量在研究太阳等离子体的结构和演化方面存在局限性,因为它们无法区分空间和时间变化。为了克服这一限制并提高我们对行星际闪烁的理解,我们同时观测了两个共轨航天器:ESA火星快车(MEX)和中国国家航天局天文一号(TIW-1)传输的无线电信号。我们在2021年4月至11月期间使用塔斯马尼亚大学8.4 GHz的VLBI射电望远镜进行了观测。我们采用行星射电干涉仪和多普勒实验(PRIDE)技术来确定载波信号的地心多普勒测量值和剩余相位。这些观测数据被用来量化由太阳风和行星际介质中的流体动力学湍流引起的航天器信号的相位波动。从两个航天器上测量到的相位波动均方根值显示出微小的差异,这些差异是由航天器的运动、机载电子设备和通过地球电离层的上行信号路径的变化等因素引起的。这些波动随太阳伸长而减小,并与太阳辐射通量在10.7 cm (2800 MHz)相关,表明太阳活动。沿着MEX和TIW-1的射电视线估计的总电子含量是相似的,在太阳延伸率较低的地方有较高的值。同时进行的多航天器观测还使RFI特性、频繁的航天器性能比较以及太阳活动对航天器性能和科学成果的影响的研究成为可能。
期刊介绍:
Many new instruments for observing astronomical objects at a variety of wavelengths have been and are continually being developed. Furthermore, a vast amount of effort is being put into the development of new techniques for data analysis in order to cope with great streams of data collected by these instruments.
Experimental Astronomy acts as a medium for the publication of papers of contemporary scientific interest on astrophysical instrumentation and methods necessary for the conduct of astronomy at all wavelength fields.
Experimental Astronomy publishes full-length articles, research letters and reviews on developments in detection techniques, instruments, and data analysis and image processing techniques. Occasional special issues are published, giving an in-depth presentation of the instrumentation and/or analysis connected with specific projects, such as satellite experiments or ground-based telescopes, or of specialized techniques.