A two-step method to detect broadcast ephemeris unavailable periods caused by BeiDou satellite orbital maneuvers

The space constellation of the BeiDou navigation satellite system(BDS) is a hybrid constellation containing medium earth orbit(MEO) satellites, geostationary earth orbit(GEO) satellites, and inclined geosynchronous orbit(IGSO) satellites. Due to the geosynchronous characteristics of GEO and IGSO, GEO satellites and IGSO satellites often need to perform orbital maneuvers, which can affect the signal-inspace(SIS) availability performance of BeiDou satellites. A two-step detection method for BeiDou satellite orbital maneuvers has been proposed in this paper. The first step is to identify orbital maneuvers based on time series analysis of broadcast ephemeris, and the second step is to verify orbital maneuvers based on bidirectional orbit prediction. The two-step detection method was used to detect the orbital maneuvers of BeiDou satellites in 2019. Through the double guarantees of identification and verification,the detection accuracy of BeiDou satellite orbital maneuvers has been effectively improved. And the orbital maneuver detection results are continued to be used to assess the SIS availability of BeiDou satellites. The results show that the availability loss of GEO satellite orbital maneuvers is about 0.45%-1.07%, and the availability loss of IGSO satellite orbital maneuvers is about 0.12%-0.19%.

Optimal maneuvering strategy of spacecraft evasion based on angles-only measurement and observability analysis

Spacecraft orbit evasion is an effective method to ensure space safety. In the spacecraft’s orbital plane, the space non-cooperate target with autonomous approaching to the spacecraft may have a dangerous rendezvous. To deal with this problem, an optimal maneuvering strategy based on the relative navigation observability degree is proposed with angles-only measurements. A maneuver evasion relative navigation model in the spacecraft’s orbital plane is constructed and the observability measurement criteria with process noise and measurement noise are defined based on the posterior Cramer-Rao lower bound. Further, the optimal maneuver evasion strategy in spacecraft’s orbital plane based on the observability is proposed. The strategy provides a new idea for spacecraft to evade safety threats autonomously. Compared with the spacecraft evasion problem based on the absolute navigation, more accurate evasion results can be obtained. The simulation indicates that this optimal strategy can weaken the system’s observability and reduce the state estimation accuracy of the non-cooperative target, making it impossible for the non-cooperative target to accurately approach the spacecraft.

Investigation of Novel Hydrogen/Oxygen Thruster for Orbital Maneuver in Space Station

Hydrogen and oxygen orbital maneuver thruster, based on gas-dynamic resonance ignition, is a new liquid rocket propulsion technology, and is especially applicable to space station. By means of theoretic thermodynamic calculation of the hydrogen and oxygen thruster, combined with the experimental exploration on the coaxial hydrogen and oxygen resonance ignition, a scheme of the thruster head configuration is designed as the combination of a coaxial hydrogen/oxygen resonance igniter and an oxygen augmentation injector. Through ignition tests on coaxial hydrogen/oxygen resonance igniter characterization, the thruster head ignition tests have been conducted successfully in sequence of resonance ignition and oxygen augmentation combustion. Finally, the thruster ground tests are successfully carried out in forms of single impulse, successive double impulses and 3.0 seconds continuous running, which verify the reliability and feasibility of the thruster. The response time of the thruster starting is restricted within 0.2 second.

Effectiveness-based orbital optimization for servicing spacecraft

Effectiveness-based system development is an essential technology developing concept advanced by some countries,such as the U.S.A.Making use of Analytic Hierarchy Process,this paper brings forward a methodology for orbital optimization based on effectiveness in the case of the orbital deployment for the Servicing Spacecraft(SSC),which needs to accomplish many types of tasks and whose orbit is affected by kinds of factors with contradictions in orbital parameter selection.Firstly,the possible tasks of SSC are decomposed and their degrees of importance are given by the times,probabilities,values of their applications.Then,the supporting capabilities are discussed from the viewpoint of orbit design,and the determination of their weights is put forward.Finally,the relationships between the orbital parameters and the effectiveness are established by using effective function,and three synthesizing methods for a single task and its capabilities are presented.

在轨服务飞行器服务范围的定量分析

为了分析单艘在轨服务飞行器的最大服务范围,综合轨道动力学和球面几何学原理,利用经典二体动力学模型、霍曼转移轨道模型以及球面三角的几何关系,得出了一定机动能力的OSV(on-orbit service vehicle).从待机轨道出发,通过改变轨道平面和改变轨道高度能够到达的最大服务范围的计算方法,设计了不同高度、倾角和机动能力OSV服务范围的仿真算例,给出了直观的对比图,分析了服务范围与各种参数的关系和变化规律.该方法定量分析了单艘OSV的服务范围,指出该范围是三维空间中的轮环形空域,据此提出待机轨道的选择要使OSV的服务范围包含服务目标的运行轨道.

小卫星姿态大角度机动联合控制算法

由于星上能源需求、空间目标探测和地面目标跟踪定向的要求 ,小卫星必须具备姿态大角度机动能力 .基于磁力矩器和反作用飞轮联合控制 ,提出了一种绕瞬时欧拉轴旋转的机动控制算法 .该算法根据运动学原理规划姿态机动的时间最短轨迹设计控制器进行跟踪 ,以实现时间较短的姿态大角度机动控制 .仿真结果表明 ,算法鲁棒性好 ,设计简单且易于在轨实时计算 。

Recover the abnormal positioning,velocity and timing services caused by BDS satellite orbital maneuvers

The BeiDou Navigation Satellite System(BDS)provides global Positioning,Velocity,And Timing(PVT)services that are widely used in various areas.The BDS satellites frequently need the orbit maneuvers due to various perturbations to keep satellites in their designed positions.During these maneuvers,PVT services may be abnormal if the data from a maneuvering satellite is used.In this paper we developed an approach to recover the abnormal PVT services.By using BDS observations from multiple tracking stations,the orbital errors of a maneuvering satellite can be in real time obtained and corrected,thereby avoiding any influence on the performance of PVT services.The tests show that the average precision of position,velocity and timing services are improved by 0.8 m,0.1 mm/s and 0.16 ns,respectively,using the developed orbital maneuver recovery approach.In addition,the approach can also be used for the orbital maneuver detection and monitoring.

空间平台机动变轨自主导航研究

针对空间平台在高轨道机动变轨过程中自主导航的需求,采用了基于Kalman滤波器的捷联惯导与星敏感器的组合导航方案。结合Kalman滤波中协方差更新的误差分配分析方法,分析了影响空间平台状态估计误差的主要因素。采用适用于高轨道的球谐重力模型,运用STK工具包设计了变轨机动轨迹,将该轨迹应用于组合导航方案的仿真验证。仿真结果表明,量测噪声是影响空间平台姿态精度的主要因素,加速度计零偏对变轨过程速度精度有决定性影响,改善两者的精度可以实现空间平台机动变轨的高精度自主导航。

预定目标的在轨服务飞行器待机轨道分析

为确定单艘在轨服务飞行器(on-orbit Service Vehicle,OSV)针对预定目标的待机轨道,综合轨道动力学和球面几何学原理,利用经典二体动力学模型、霍曼转移轨道模型以及球面三角几何关系,设置具体实例分析OSV针对低、中、高轨道目标的待机轨道选择方法,得到轨道平面调整的能耗和变轨位置与目标轨道平面参数的变化关系,提出待机轨道参数优化的一般思路。该研究可为OSV实施"一对一"在轨服务的待机轨道选择提供理论依据。

考虑J_2项摄动的空间共振轨道特性分析

共振轨道是建立在新型坐标系下的非开普勒轨道,应用于空间机动轨道的设计,具有节省能量的优势。针对地球形状摄动J_2项对共振轨道特性的影响分析问题,建立了一种新的考虑J_2项摄动影响的共振轨道数学模型。通过与传统受J_2项摄动影响的共振轨道数学模型的仿真对比分析可以看出,新的数学模型虽然形式较为复杂,但却能够揭示不同阶段J_2项摄动使系统产生偏差的原因,比传统模型更为精确,因此更适用于工程实际中分析J_2项摄动对共振轨道特性的影响。

Research on the strategy of angles-only relative navigation for autonomous rendezvous

This paper considers the problem of angles-only relative navigation for autonomous rendezvous. Methods for determining degree of observability （DO0） and latent range information of orbital maneuver are proposed for analyzing and enhancing the precision of relative position and velocity estimation. The equations of angles-only relative navigation are set forth on the con- dition that optical camera is the only viable sensor for relative measurement, and expressions for the DO0 of relative navigation are obtained by using the Newton iterative method. The latent range information of orbital maneuver is analyzed, which is employed to enhance the DOO of angles-only relative navigation. Simulation result shows that DOO is effective to describe the observability level of relative position and velocity, and the latent range information is useful in enhancing the DOO of the angles-only relative navigation.