针对地面站无法对月球背面着陆器定位的问题，分别对月球背面着陆器利用月球轨道器上行信号和地月L2中继星上行信号的多普勒对其定位的两种模式进行了研究。在月固坐标系下，理论分析了两种模式下轨道器的多普勒定位精度，以及几何精度因子及频率稳定度对定位精度的影响。在STK软件中对两种定位模式建模，利用其导出的星历数据定量评估了两种定位模式下着陆器的定位精度，讨论了应用两种定位模式应满足的时间约束和空间约束条件，同时定量分析给出了不同载频、不同观测时间长度下，着陆器时钟应该满足的频率稳定度。%To overcome the drawback that the ground station on the earth could not position the lunar lander on the far side of the moon, two solutions were investigated. One solution is to position the lu⁃nar lander by measuring the Doppler frequency of downlink signal transmitted by the lunar orbiter and the other is by measuring the Doppler frequency of the signal from an earth⁃moon L2 relay satellite. In the lunar fixed coordinate system, the Doppler positioning precisions of the two solutions were analyzed respectively for the lunar lander. The influences of the dilution of precision and frequency stability on the positioning precision were analyzed. These two Doppler lunar lander positioning scenarios were modeled in STK( Satellite Tool Kit) , and the exported ephemerides were used to evaluate the positio⁃ning precision quantitatively. Meanwhile, the time constraints and spatial constraints of the two solu⁃tions were discussed. The frequency stability requirements for the clock of the lunar lander were given quantitatively with respect to different carrier frequencies and different observing time.
展开▼
