Development of three dimensional orbit determination by Doppler measurement between two satelites

我们试图通过研究与多普勒测量有关的可能误差源和开发电离层和对流层的新模型来获得最高的多普勒测量精度。首先通过测量卫星发射载波的频率稳定性和相位噪声，推导出卫星自旋对相位变化的影响。然后，我们利用多普勒和VLBI数据进行了轨道确定模拟，结果表明，多普勒和VLBI数据相结合可以更好地恢复翼部附近重力场，而单靠多普勒测量很难恢复翼部附近重力场。接下来，我们对一种新的轨道确定方法进行了模拟，以了解如何在SELENE任务的情况下很好地恢复重力场。将VLBI与2路和4路多普勒测量相结合，可以提高模型中所有系数的精度。这里考虑的包括VLBI数据对确定Rstar精确轨道的影响，这是4路多普勒测量的参考。通过添加VLBI数据，小于33度的系数将提高约2倍，其中2度系数的改善效果最好，提高了2.6倍。如果我们能够通过适当的力模拟使R/Vstar弧长大于1天，那么SELENE重力场的最终精度将比LP100J在30度以下的精度提高一个数量级。

We try to attain the highest accuracy in Doppler measurements by investigating possible error sources related to the Doppler measurements and by developing a new model of the ionosphere and the troposphere. First of all we formulated the effect of spin of a satellite on phase change after we measured frequency stability and phase noise of carrier wave emitted from the satellite. Next, we did a simulation of orbit determination by using Doppler and VLBI data and showed that gravity field near the limb, which was poorly recovered only by Doppler measurements, would be better recovered by combining the Doppler and VLBI data. Next, we ran a simulation of a new method for orbit determination in order to know how the gravity field would be well recovered for the case of SELENE mission. Accuracies of all the coefficients included in the model will be improved by combining VLBI with 2-way and 4-way Doppler measurements. What is accounted for here includes the effect of VLBI data on determining the precise orbit of the Rstar which is a reference of 4-way Doppler measurement. By adding VLBI data, the coefficients of degrees less than 33rd will be improved by about a factor of 2, with the best improvement in the 2nd degree coefficient by a factor 2.6. If we could make R/Vstar arc length to be longer than 1 day by proper force modeling, the final accuracy of SELENE gravity field will be one order of magnitude better than that of LP100J below degree around 30.