地球静止轨道通信卫星位置保持原理及实施策略

本文从工程应用的角度详尽地介绍了同步通信卫星在定点位置漂移的原因及计算方法，以我国在轨运行的东方红三号卫星和风云二号卫星为例，给出了大量工程实测数据，并给出了定点保持实施策略，它们已经成功地运用到我国在轨同步卫星的管理。     

Families of halo orbits in the elliptic restricted three-body problem for a solar sail with reflectivity control devices

Solar sail halo orbits designed in the Sun-Earth circular restricted three-body problem (CR3BP) provide inefficient reference orbits for station-keeping since the disturbance due to the eccentricity of the Earth’s orbit has to be compensated for. This paper presents a strategy to compute families of halo orbits around the collinear artificial equilibrium points in the Sun-Earth elliptic restricted three-body problem (ER3BP) for a solar sail with reflectivity control devices (RCDs). In this non-autonomous model, periodic halo orbits only exist when their periods are equal to integer multiples of one year. Here multi-revolution halo orbits with periods equal to integer multiples of one year are constructed in the CR3BP and then used as seeds to numerically continue the halo orbits in the ER3BP. The linear stability of the orbits is analyzed which shows that the in-plane motion is unstable while the out-of-plane motion is neutrally stable and a bifurcation is identified. Finally, station-keeping is performed which shows that a reference orbit designed in the ER3BP is significantly more efficient than that designed in the CR3BP, while the addition of RCDs improve station-keeping performance and robustness to uncertainty in the sail lightness number.     

一种新的共线平动点拟周期轨道稳定保持策略

限制性三体问题下共线平动点附近的拟周期轨道在深空探测中具有重要的实际应用价值,得到了各航天大国的广泛重视。通过将动力学中心流形结构引入轨道控制方法的设计之中,得到了基于投影到中心流形的共线平动点拟周期轨道稳定保持策略。首先推导了会合坐标到中心流形坐标的正则变换方法,在此基础上设法通过引入轨道机动,将偏差状态点投影到中心流形上,从而达到消除不稳定分量的目的。该方法充分整合了平动点的动力学特性,并且也适用于周期轨道的稳定保持。通过对Lissajous轨道和晕轨道的数值仿真表明,该方法较以往方法具有更强的稳定性,能在显著降低轨控燃料消耗的基础上达到较好的稳定保持效果。     

卫星编队飞行相对位置保持的脉冲控制

研究了卫星编队飞行相对位置保持的脉冲控制方法。分析基于动力学模型的周期脉冲控制策略,讨论其工程可实现性,并在考虑存在较大测量噪声情况下提出了周期多步脉冲控制的方法。数字仿真的结果比较显示了这种多步脉冲控制方法的有效性。     

Analysis of long-endurance station-keeping flight scenarios for stratospheric airships in the presence of thermal effects

The ability to achieve long-endurance station-keeping flights makes stratospheric airships desirable platforms for the provision of communication and surveillance services. To maintain long-endurance flights, it is necessary to consider the problem of energy consumption. In this paper, we discuss long-endurance flight scenarios of stratospheric airships in the presence of thermal effects. The balance between buoyancy and gravity is influenced by thermal effects during the diurnal cycle. We perform a theoretical analysis based on the helium’s mass, pressure differential, and altitude as the main factors. To verify the effectiveness of the control over the pressure differential and the altitude, three long-endurance flight scenarios are proposed and compared. Then, the corresponding optimization problems are constructed to determine the energy-minimum flight. Finally, further efforts are made to reduce energy consumption. The realization and limitations of two strategies for improvement are analyzed. A comparison with other scenarios shows the effectiveness of energy conservation. The study in this paper thus provides a reference for station-keeping applications of stratospheric airships.     

On two kinds of intermediate orbits for asteroid explorations

In the paper, two kinds of intermediate orbits for asteroid explorations are proposed. One is around the collinear libration points of the Sun-asteroid restricted three-body problem. The other is around the asteroid itself. The first kind of intermediate orbit is applicable to asteroids with known masses, while the second is suitable for asteroids with unknown or negligible masses. Analytical solutions of these two intermediate orbits in the simplified models are introduced first, and then numerical algorithms are used to refine them to obtain the true orbits in the real force model. At last, the problem of station-keeping is addressed. The linear optimal feedback control law is used, and numerical simulations are made to both kinds of intermediate orbits. The results show that both kinds of orbits are feasible. The cost is reasonable and mainly depends on the initial insertion error.     

Integrated guidance and control for solar sail station-keeping with optical degradation

Current control approaches for solar sail station-keeping on libration point orbits have not considered the degradation of the sail’s optical properties. However, significant optical degradation could lead to poor station-keeping performance or even complete failure. This paper presents an integrated guidance and control strategy to address this problem by updating the reference orbit based on in situ estimation. An exponential optical degradation model is incorporated into the solar radiation acceleration model, and an on-line reference orbit update approach is incorporated into the station-keeping, coupled with an active disturbance rejection controller. The reflection coefficient is estimated on-line and the reference orbit is updated discretely when the optical properties have degraded by a prescribed amount. This strategy provides discrete updates to the reference orbits such that the perturbation due to the optical degradation is maintained within a small range. These smaller perturbations can be dealt with by the controller’s robustness and station-keeping can be sustained for long durations even in the presence of large optical degradation.     

East–West Station-Keeping maneuver strategy for COMS satellite using iterative process

The first Korean multi-mission geostationary satellite, Communication, Ocean, and Meteorological Satellite (COMS) will be launched in 2010. The missions of this satellite will be Ka-band communications, ocean color monitoring, and meteorological imaging. The satellite was designed with only one solar array on the south panel. This novel configuration will keep imaging instruments on the north side from heating up. Asymmetry of the spacecraft configuration requires twice-a-day thruster-based Wheel Off-Loading (WOL) operations to keep the satellite attitude for imaging and communication. Thruster firings during the WOL operations cause the satellite orbit to change two times a day. Weekly East–West Station-Keeping (EWSK) and North–South Station-Keeping (NSSK) maneuver operations are planned for the COMS satellite in order to maintain the satellite in ±0.05° box at 128.2°E longitude.     

Nonlinear dynamics and station-keeping control of a rotating tethered satellite system in halo orbits

The dynamics of a rotating tethered satellite system （TSS） in the vicinity of libration points are highly nonlinear and inherently unstable. In order to fulfill the station-keep control of the rotating TSS along halo orbits, a nonlinear output tracking control scheme based on the θ- D technique is proposed. Compared with the popular time-variant linear quadratic regulator （LQR） controller, this approach overcomes some limitations such as on-line computations of the algebraic Riccati equation. Besides, the obtained nonlinear suboptimal controller is in a closed form and easy to implement. Numerical simulations show that the TTS trajectories track the periodic reference orbit with low energy consumption in the presence of both tether and initial injection errors. The axis of rotation can keep pointing to an inertial specific object to fulfill an observation mission. In addition, the thrusts required by the controller are in an acceptable range and can be implemented through some low-thrust propulsion devices.