Astrodynamics最新文献

To match the trans-lunar injection with high accuracy, a near-optimal orbit control method for phasing loops is proposed. Sensitivity analysis was performed based on Gauss’s variational equations, and a near-optimal orbit control strategy was developed. A sequential shooting method was proposed to reduce the dimensions of each shooting problem and improve convergence. To satisfy the accessibility requirements of ground facilities, a maneuvering location adjustment strategy is proposed. The advantage of the delta-V saving of the near-optimal method was verified by comparing with the differential correction method. The robustness of the practical method was verified using Monte Carlo simulations with high-fidelity dynamics. The results of this study can be applied to midcourse correction of phasing loops before the trans-lunar injection of a lunar probe.

The mapping phase is a key stage of the Tianwen-1 orbiter. It has the longest exploration time and gathers abundant radio tracking data via the Chinese deep space network. Thus, it also provides opportunities for radio science research topics such as the Mars gravity field model, ephemeris, and radio occultation experiments. At this stage, the need for imaging takes the highest priority, leading to frequent attitude adjustments for the spacecraft, which presents challenges for Precise Orbit Determination (POD). To improve the accuracy of the spacecraft’s orbit, this study analyzes the effects of arc length, the empirical acceleration, and the solar radiation pressure parameters on POD, considering the limited number of radio tracking observations. For one-day arcs, the POD is not able to adequately account for wheel off-loading and a few unknown forces with limited observations, but reasonable fitting is performed for the wheel off-loading occurring during tracking periods or the gap between two tracking periods. When extending the POD arc to three days, the estimated empirical acceleration can be well-fitted and reflects the aggregation feature, but the solar radiation pressure parameter has little impact on POD results. The root mean square of two-way range-rate residuals after POD is about 0.18–0.35 mm/s; the orbital position accuracy of 60% of the arcs is better than 100 m.

Ground- and space-based optical observation is an efficient way to catalog objects in the cislunar space. Initial orbit determination based on optical data is still an open problem for cislunar objects. The motion of these objects usually follows the law of three bodies instead of the two-body one, so current algorithms based on the two-body relation should be revised. Moreover, due to the long duration of most cislunar objects, optical observations of even hours can cover only a small fraction of one orbit, making the initial orbit determination of these objects a typical too-short-arc problem, which is difficult. A way to address this problem is to use the admissible region. In this study, an efficient algorithm constrained by the admissible region is proposed. It is easy to implement because it uses only simple iterations. Its efficiency is proven by comparing it with that of one traditional initial orbit determination algorithm.

The deployment of a long tether to operate as a partial space elevator, starting from a nucleus in geostationary orbit, is studied. Uncontrolled deployment is an inherently unstable process because the center of orbit gradually decreases from the geostationary altitude when deployment progresses. It is also observed that the elasticity of the tether has an important effect on deployment stability. It is shown that the application of a transverse force on the main spacecraft, determined by using linear state feedback and appropriate gains, can stabilize the deployment. An LQR controller is developed. Simulations of the dynamics of the system are carried out using this controller for various parametric values of tether elasticity, deployment rates, etc., to evaluate the efficacy of the controller.

A novel hybrid scheme for the maneuver detection and estimation of a noncooperative space target was proposed in this study. The optical measurements, together with the range and range rate measurements from the ground-based radars, were used in the tracking scenarios. In many tracking scenarios, radar resources for non-cooperative targets are constrained, particularly for near-earth targets, where multiple objects can only be tracked by a single radar at a time. This limitation hinders the accurate estimation of noncooperative target maneuvers, and can at times result in target loss. Existing literature has addressed this issue to some extent through various maneuvering target-tracking methods. To address this problem, a hybrid maneuver detection and estimation method that combines the input detection and estimation extended kalman filter and the weighted nonlinear least squares method is presented. Simulation results demonstrate that the proposed method outperforms the previous method, offering more accurate and efficient estimations.

A new attitude control method for solar sails is proposed using a single-axis gimbal mechanism and three-axis reaction wheels. The gimbal angle is varied to change the geometrical relationship between the force due to solar radiation pressure (SRP) and the center of mass of the spacecraft, such that the disturbance torque is minimized during attitude maintenance for orbit control. Attitude maneuver and maintenance are performed by the reaction wheels based on the quaternion feedback control method. Even if angular momentum accumulates on the reaction wheels due to modelling error, it can also be unloaded by using the gimbal to produce suitable torque due to SRP. In this study, we analyzed the attitude motion under the reaction wheel control by linearizing the equations of motion around the equilibrium point. Further, we newly derived the propellent-free unloading method based on the analytical formulation. Finally, we constructed the integrated attitude-orbit control method, and its validity was verified in integrated attitude-orbit control simulations.

This study analyzes the optimal transfer trajectory of a spacecraft propelled by a spin-stabilized electric solar wind sail (E-sail) with a single conducting tether and a spin axis with a fixed direction in an inertial (heliocentric) reference frame. The approach proposed in this study is useful for rapidly analyzing the optimal transfer trajectories of the current generation of small spacecraft designed to obtain in-situ evidence of the E-sail propulsion concept. In this context, starting with the recently proposed thrust model for a single-tether E-sail, this study discusses the optimal control law and performance in a typical two-dimensional interplanetary transfer by considering the (binary) state of the onboard electron emitter as the single control parameter. The resulting spacecraft heliocentric trajectory is a succession of Keplerian arcs alternated with propelled arcs, that is, the phases in which the electron emitter is switched on. In particular, numerical simulations demonstrated that a single-tether E-sail with an inertially fixed spin axis can perform a classical mission scenario as a circle-to-circle two-dimensional transfer by suitably varying a single control parameter.

A precise dynamic model for towing and removing a defunct satellite with solar panels in orbit using a tethered net often has low computational efficiency owing to the complex contact and collision between the net and panels, which is not conducive to research. To solve this problem, a “single main tether–multiple subtether” bifurcation structure with beads was employed as the tethered net model. This study investigated the dynamics of tethered defunct satellites with solar panels, particularly the behavior of the attitude of the tethered satellite, oscillation of the main tether, and vibration of solar panels under different conditions. The results showed that different attachment configurations of the subtethers and the flexibility of the main tether have an evident impact on the dynamic characteristics of the system.