Li Jie, Zhu Jun, Ruan Rengui, Xu Xiaolong, Fang Yanan, Wang Chong, Huyan Zongbo
State Key Laboratory of Astronautic Dynamics, Xi'an, Shanxi, China.
State Key Laboratory of Geo-Information Engineering, Xi'an, Shanxi, China.
Sci Rep. 2025 Apr 25;15(1):14438. doi: 10.1038/s41598-025-98560-5.
The Ka-band Inter-Satellite Links (ISL) has been introduced as an innovative measurement technique for orbit determination (OD) and time synchronization (TS) of the global BeiDou Navigation Satellite System (BDS-3), complementing traditional L-band ground-satellite tracking. For the first time, OD and TS have been conducted for the entire full-operational constellation of BDS-3 using raw one-way ISL data. The normal equation (NEQ) accumulation technique is employed to estimate critical parameters, such as the ISL hardware delays (Ka-biases), to derive long-term average solutions. With the support of ISL, an orbital accuracy of 8.0 cm for Medium Earth Orbits (MEOs), 11.6 cm for Inclined Geosynchronous Orbits (IGSOs), and 24.0 cm for Geostationary Orbits (GEO) can be achieved using a ground network consisting of 20 stations. An extended observation model was developed for ISL heterogeneous data at both ends due to the presence of a specialized GEO satellite C61 which exclusively provides ISL data without broadcasting civil L-band signals. Subsequently, the OD and TS capabilities were validated using one-way ISL for GEO C61, resulting in an OD accuracy of approximately 3.7 cm in the radial direction, 7.9 cm in the normal direction, 27.7 cm in the tangential direction, and 29.0 cm in 3-D position; with a TS accuracy of around 0.1 ns. In most cases, one-way ISL transmission and reception Ka-biases remain stable over considerable periods, achieving an accuracy of 0.2 ns. However, apparent abnormal jumps in Ka-bias were observed, which were determined to be sudden changes in L-band hardware delay from navigation signals rather than jumps in ISL hardware delay itself. This finding marks the distinction between L-band hardware delay jumps and atomic clock jumps for navigation satellites. Additionally, the residuals of one-way ISLs exhibit periodic terms. Investigations indicate that these residuals vary with the antenna azimuth and elevation angles of each link and are specific to individual satellites. This variation may be attributed to small deviations in the on-board ISL receivers or antennas. This discovery is valuable for modeling ISL observations.
Ka波段星间链路（ISL）已被引入，作为一种创新的测量技术，用于全球北斗导航卫星系统（BDS-3）的轨道确定（OD）和时间同步（TS），以补充传统的L波段地面卫星跟踪。首次使用原始单向ISL数据对BDS-3的整个全运行星座进行了OD和TS。采用正规方程（NEQ）累积技术来估计关键参数，如ISL硬件延迟（Ka偏差），以得出长期平均解。在ISL的支持下，使用由20个站组成的地面网络，可以实现中地球轨道（MEO）的轨道精度为8.0厘米，倾斜地球同步轨道（IGSO）为11.6厘米，地球静止轨道（GEO）为24.0厘米。由于存在专门的地球静止轨道卫星C61，其专门提供ISL数据而不广播民用L波段信号，因此为两端的ISL异构数据开发了扩展观测模型。随后，使用GEO C61的单向ISL对OD和TS能力进行了验证，在径向方向上的OD精度约为3.7厘米，法向方向为7.9厘米，切向方向为27.7厘米，三维位置为29.0厘米；TS精度约为0.1纳秒。在大多数情况下，单向ISL发射和接收Ka偏差在相当长的时间内保持稳定，精度达到0.2纳秒。然而，观察到Ka偏差出现明显的异常跳变，确定这是导航信号中L波段硬件延迟的突然变化，而不是ISL硬件延迟本身的跳变。这一发现标志着导航卫星L波段硬件延迟跳变与原子钟跳变之间的区别。此外，单向ISL的残差呈现周期性项。调查表明，这些残差随每个链路的天线方位角和仰角而变化，并且特定于各个卫星。这种变化可能归因于机载ISL接收器或天线的小偏差。这一发现对于ISL观测建模具有重要价值。
