同波束VLBI测量下的天问一号火星车定位及精度分析

Positioning and Accuracy Analysis of Tianwen-1 Mars Rover Based on Same-Beam VLBI Measurement

  • 摘要: 针对中国天问一号火星探测任务中的火星车定位问题,进行了相关方法的研究和精度分析。根据现有测控条件,考虑到火星车无地面测距数据,提出了利用轨道器和火星车的同波束甚长基线干涉测量(same-beam very long baseline interferometry,SBI)数据对火星车进行定位的方法。由于利用SBI联合轨道器测距数据无法在定轨定位的同时解算差分相时延模糊度,分析了在固定轨道器的轨道情况下,仅利用SBI数据进行火星车定位。结果表明,火星车定位误差随着轨道器的轨道精度提高而减小,如果轨道器的轨道精度从1 km提升到100 m或10 m,6 h SBI数据可以将火星车定位精度提高到数百米,同时,增加数据弧段可进一步提高定位精度,当对着陆器高程方向进行约束时,定位精度会有明显改善。

     

    Abstract:
      Objectives  Aiming at the problem of rover positioning in Chinese Mars exploration mission Tianwen-1, the related research and accuracy analysis have been carried out.
      Methods  According to the existing measurement and control system and considering that the rover has no ground ranging data, we proposed a method to locate the rover using same-beam very long baseline interferometry (SBI) data of the orbiter and rover. Since it is not possible to determine the ambiguity using SBI and ranging data while determining the orbit and positioning the rover at the same time, the proposed method which only uses SBI data for the rover positioning under the fixed orbital situation is analyzed.
      Results  The results show that the rover positioning error decreases with the increase of orbital accuracy. If the orbital accuracy is increased from 1 km to 100 m or 10 m, the rover positioning error using 6-hour SBI data can be reduced to hundreds of meters.
      Conclusions  More data can further reduce the positioning error and the positioning accuracy can be improved obviously with an elevation constraint.

     

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