| 摘要: |
| 在欧洲空间局和日本宇宙开发机构联合开展的BepiColombo水星任务中，将开展水星轨道器无线电科学实验，包括估计水星的引力场及其旋转状态，并对广义相对论进行验证。目前地面系统和星上设备的主流配置可以在无线电科学实验中建立X/X、X/Ka和Ka/Ka多个频段的链路，测速精度可达3 um/s（1 000 s积分），测距精度为20 cm。提出了基于时延机械噪声对消技术提高无线电科学实验性能的方案。时延机械噪声对消技术需要处理在两个测站不同时刻的测量数据，一个测站实施双向多普勒测距，对另一个单收测站的要求较为严格，该测站需要具有较好的对流层条件。这种方法能够显著降低Ka频段双向链路的主要测量噪声，包括由对流层和天线机械系统震动引起的噪声。我们给出了端到端的仿真性能，并估计了在使用时延机械噪声对消技术前提下的水星引力场和旋转状态。考虑使用NASA位于美国本土戈尔德斯敦的DSS-25天线或欧空局位于阿根廷马拉圭的DSA-3天线作为双程测量站，并考虑使用位于智力的APEX天文观测天线作为单收站。分析结果表明在最好的噪声条件下，使用DSA-3天线作为双程测量站时，时延机械噪声对消技术可将待估计的全局和局部参数的估计精度提升一倍。对于无线电科学实验的目标，这一可能的性能提升对行星地质物理学很有意义，它将有益于研究水星内部的结构。 |
| 关键词: 水星 BepiColombo 水星轨道器无线电科学实验 多普勒 时延机械噪声对消技术 |
| DOI：10.15982/j.issn.2095-7777.2018.02.002 |
| 分类号:V11 |
| 基金项目: |
|
| Improvement of BepiColombo’s Radio Science Experiment Through an Innovative Doppler Noise Reduction Technique |
|
MARIANI M J, DI RUSCIO A, NOTARO V, IESS L
|
|
Department of Mechanical and Aerospace Engineering, Sapienza University of Rome, Rome 00184, Italy
|
| Abstract: |
| The Mercury Orbiter Radio science Experiment (MORE), onboard the ESA/JAXA BepiColombo mission to Mercury, is designed to estimate Mercury's gravity field, its rotational state, and to perform tests of relativistic gravity. The state-of-the-art onboard and ground instrumentations involved in the MORE experiment will enable to establish simultaneous X/X, X/Ka and Ka/Ka-band links, providing a range rate accuracy of 3 μm/s (at 1 000 s integration time) and a range accuracy of 20 cm. The purpose of this work is to show the improvement achieved on MORE's performance by means of the Time-Delay Mechanical Noise Cancellation (TDMC) technique. The TDMC consists in a combination of Doppler measurements collected (at different times) at the two-way antenna and at an additional, smaller and stiffer, receive-only antenna located in a site with favorable tropospheric conditions. This configuration could reduce the leading noises in a Ka-band two-way link, such as those caused by troposphere and ground antenna mechanical vibrations. The results of end-to-end simulations and estimation of Mercury's gravity field and rotational state considering the TDMC technique are presented. The results for a two-way link from NASA's DSS-25 (in Goldstone, CA) or from ESA's DSA-3 (in Malargue, Argentina) are compared, while the APEX is assumed as the receive-only antenna. It shows that in best-case noise conditions, the TDMC technique allows to obtain a factor-of-two accuracy gain on both global and local parameters, considering DSA-3 as a two-way antenna. Such improvement in the scientific objectives of MORE is of geophysical interest as it could provide a constraint on the interior structure of Mercury. |
| Key words: Mercury BepiColombo Mercury Orbiter Radio science Experiment Doppler Time-Delay Mechanical Noise Cancellation |
