The Tianping-1B is a 20-kg low earth orbit nanosatellite with a commercial multi-GNSS receiver based on a microelectromechanical system. This receiver collects concurrent code and phase dual-frequency measurements from the global positioning system (GPS) and the second and third generations of the BeiDou Global Navigation Satellite System (i.e., BDS-2 and BDS-3). However, BDS-3 signals with pseudorandom noise code numbers greater than 32 cannot be received. In this study, onboard GPS and BDS measurements from Tianping-1B are collected for days 133–147 of 2019. The performance of the onboard BDS-3 measurements is analyzed, and the potential of the BDS-3-based precise orbit determination (POD) for Tianping-1B is assessed. The carrier-to-noise-density ratio of the BDS-3 is higher than that of the BDS-2 and approaches that of the GPS. The BDS-3 has a smaller code multipath error than the BDS-2 and the GPS and therefore a higher quality of code measurements. The results of the overlap comparison show a GPS-based orbit consistency below 3.5 cm in three dimensions (3D) and below 1.2 cm in the radial direction. The mean of satellite laser ranging validation residual RMS is 1.7 cm. The orbit obtained using onboard BDS measurements is assessed using the GPS-based orbit as a reference: The mean 3D root mean square (RMS) difference between the BDS-3-only-based POD and the reference orbit is 4.57 cm. Thus, a sub-dm-level orbit can be achieved using only onboard BDS-3 measurements. A POD with slightly higher precision than the BDS-3-only-based POD is obtained using both BDS-3 and BDS-2 measurements, using higher weights for the BDS-3 data than the BDS-2 data. Then, the combined BDS-3/GPS POD is performed: The RMS difference between this joint orbit and the GPS-based orbit is 1 cm in 3D. This study can be used as a reference for the development of BDS-3 based POD, which will approve in accuracy and precision upon completion of BDS-3.

中文翻译：

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使用BDS-3对LEO纳米卫星进行高精度轨道测定

天平1B是20公斤低地球轨道纳米卫星，带有基于微机电系统的商用多GNSS接收器。该接收机从全球定位系统（GPS）以及北斗第二代和第三代全球导航卫星系统（即BDS-2和BDS-3）收集并发代码和相位双频测量值。但是，不能接收伪随机噪声代码数大于32的BDS-3信号。在这项研究中，收集了天平1B号在2019年133-147天的机载GPS和BDS测量结果。分析了机载BDS-3测量结果的性能，以及基于BDS-3的精确轨道确定（POD）的潜力）用于天平1B。BDS-3的载噪比高于BDS-2，接近GPS。与BDS-2和GPS相比，BDS-3的代码多径误差更小，因此代码测量的质量更高。重叠比较的结果表明，在三个维度（3D）中，基于GPS的轨道一致性低于3.5厘米，而沿径向方向则低于1.2 cm。卫星激光测距验证残余RMS的平均值为1.7 cm。使用基于GPS的轨道作为参考评估使用机载BDS测量获得的轨道：仅基于BDS-3的POD与参考轨道之间的3D均方根（RMS）均值差为4.57 cm。因此，仅使用机载BDS-3测量就可以实现亚dm级轨道。使用BDS-3和BDS-2测量结果，可以得到比仅基于BDS-3的POD精度更高的POD，并且BDS-3数据的权重要高于BDS-2数据。然后，然后执行BDS-3 / GPS POD组合：在3D模式下，此联合轨道与基于GPS的轨道之间的RMS差为1 cm。这项研究可以作为开发基于BDS-3的POD的参考，该POD将在BDS-3完成后在准确性和精度上得到认可。