Orbit insertion uncertainties can significantly affect the configuration stability of heliocentric gravitational wave (GW) observatories, necessitating valid configuration uncertainty propagation techniques. Current configuration uncertainty propagation methods suffer from drawbacks related to their high computational complexity. To this end, this study proposes a novel configuration uncertainty propagation method for heliocentric GW observatories to reduce the computational complexity. First, the angular momentum and phase angle were found to be the two core variables for the orbit propagation of heliocentric GW observatories, the analytical solutions of which were derived using a perturbation-averaging technique. Subsequently, a first-order sensitivity matrix of the configuration stability index with respect to the initial states was derived based on the analytical solutions of the angular momentum and phase angle. Semi-analytically sensitive directions were obtained based on the derived sensitivity matrix, which was further employed to reduce the terms of configuration uncertainty propagation. The performance of the proposed method was validated using the example of a Laser Interferometer Space Antenna (LISA) project by comparing it with several competitive methods. The numerical results show that the proposed reduced-order method has a relative error close to that of the conventional full-state method and reduces the computational complexity by more than 46.

Configuration stability is essential for a space-based Gravitational-Wave (GW) observatory, which can be impacted by orbit insertion uncertainties. Configuration uncertainty propagation is vital for investigating the influences of uncertainties on configuration stability and can be potentially useful in the navigation and control of GW observatories. Current methods suffer from drawbacks related to high computational burden. To this end, a Radial-Tangential-Ddirectional State Transition Tensor (RT-DSTT)-based configuration uncertainty propagation method is proposed. First, two sensitive directions are found by capturing the dominant secular terms. Considering the orbit insertion errors along the two sensitive directions only, a reduced-order RT-DSTT model is developed for orbital uncertainty propagation. Then, the relationship between the uncertainties in the orbital states and the uncertainties in the configuration stability indexes is mapped using high-order derivatives. The result is a semi-analytical solution that can predict the deviations in the configuration stability indexes given orbit insertion errors. The potential application of the proposed RT-DSTT-based method in calculating the feasible domain is presented. The performance of the proposed method is validated on the Laser Interferometer Space Antenna (LISA) project. Simulations show that the proposed method can provide similar results to the STT-based method but requires only half of the computational time.

The confirmation of gravitational waves in recent years has set off a new upsurge of exploring the extreme interactions critical to the origin and evolution of stars, galaxies, and the universe. The detection of gravitational waves in space is expected to cover the largest number and the greatest variety of gravitational wave sources, which is more compelling and valuable than the initial detection on the ground. Orbital dynamics and control are the keys to realizing the detection of gravitational waves in space. This paper reviews the orbital mechanics for space-based gravitational wave observatories. The principle and typical gravitational wave observation mission concepts are first introduced and classified summarized. Then, the orbital mechanics of the space-based gravitational wave observatories in different spatial locations are reviewed. On the basis of the characteristics of different observatories, 2 groups of methods related to the observatory configuration design and optimization are summarized: the constellation configuration design and optimization method similar to the geocentric configuration and libration point configuration, the formation design and optimization method similar to heliocentric configuration. The prospects of space-based gravitational wave observatories are finally put forward, which shall provide a reference for future research on space-based gravitational wave observatories.

Long-term configuration stability is essential for an interferometric detection constellation (IDC), which is closely related to initial uncertainty. Therefore, it is vital to evaluate the uncertainty and characterize the configuration stability. In this study, an analytical method was developed for the configuration uncertainty propagation of a geocentric triangular IDC. The angular momentum and the argument latitude were found to be significantly affected by the initial uncertainty and were selected as the core variables. By averaging the perturbation in one revolution, an analytical solution was proposed for propagating the core orbital elements in one revolution. Subsequently, the analytical solution of the orbit elements during the mission period is obtained by multiplying the solutions in iterative revolutions. The relationship between the selected orbital elements and the configuration stability parameters was established using an analytical solution. The effects of the initial uncertainty in different directions on the configuration and stable domains were studied. Simulations show that the developed method is highly efficient and accurate in predicting the configuration stability. The relative error with respect to the Monte Carlo simulations was less than 3% with a time consumption of 0.1%. The proposed method can potentially be useful for constellation design and stability analysis.

The threat of potential hazardous near-Earth asteroid (PHA) impact on Earth is increasingly attracting public attention. Monitoring and early warning of those PHAs are the premise of planetary defense. In this paper, we proposed a novel concept of surveillance constellation of heterogeneous wide-field near-Earth asteroid (NEA) surveyors (CROWN), in which six space-based surveyors are loosely deployed in Venus-like orbits to detect the NEAs along the direction of the sunlight. First, the concept and overall design of the NEA surveillance constellation are discussed. Second, the transfer and deployment trajectory of the surveyors are investigated based on the Sun-Venus three-body system. The Sun-Venus libration orbit is taken as the parking orbit, and its stable invariant manifolds are used to reduce the deployment fuel consumption. Next, the detection performance of the CROWN was evaluated considering constraints of apparent visual magnitude and field of view. The NEA orbit determination (OD) using the CROWN was studied and verified. Simulation results show that the CROWN can be deployed with a total velocity increment of approximately 300 m/s. During the 5 years of observation, 99.8% of PHAs can be detected and the OD precision is better than a single-surveyor system. This paper can provide a reference for the construction of future asteroid defense system.

Asteroid 469219 Kamo'oalewa, also named 2016 HO3, is a small-size fast-rotating near-Earth asteroid, which is a potential target for future explorations. Owing to its weak gravity and fast spin rate, the dynamics on the surface or in the vicinity of 2016 HO3 are significantly different from those of planets or other small bodies explored in previous missions. In this study, the geophysical and orbital environments of 2016 HO3 were investigated to facilitate a potential mission design. First, the geometric and geopotential topographies of 2016 HO3 were examined using different shape models. The lift-off and escape conditions on its fast-rotating surface were investigated. Then, the periodic orbits around 2016 HO3 were studied in the asteroid-fixed frame and the Sun–asteroid frame considering the solar radiation pressure. The stable regions of the terminator orbits were discussed using different parameters. Finally, the influence of the nonspherical shape on the terminator orbits was examined. The precise terminator orbits around a real shape model of 2016 HO3 were obtained and verified in the high-fidelity model. This study shows that the polar region of 2016 HO3 is the primary region for landing or sampling, and the terminator orbits are well suited for global mapping and measurements of 2016 HO3. The analysis and methods can also serve as references for the exploration of other small fast-rotating bodies.

In recent years, exoplanet detection has become the technological frontier in the field of astronomy, because it provides evidence of the origin of life and the future human habitable exoplanet. Deploying several satellites to form an aperture-synthetic interferometer system in space may help discover “another Earth” via interferometry and midinfrared broadband spectroscopy. This paper analyzes a space-based exoplanet exploration mission in terms of the scientific background, mission profile, trajectory design, and orbital maintenance. First, the system architecture and working principle of the interferometer system are briefly introduced. Secondly, the mission orbit and corresponding transfer trajectories are discussed. The halo orbit near the Sun-Earth L2 (SEL2) orbit is chosen as the candidate mission orbit. The low-energy transfer via stable invariant manifold with multiple perigees is designed, and the proper launch windows are presented. A speed increment less than 10 m/s is imposed for each transfer to achieve the insertion of the halo orbit. Finally, the tangent targeting method (TTM) is applied for high-precision formation maintenance with the whole velocity increments of less than 5 × 10⁻⁴ m/s for each spacecraft when the error bound is 0.1 m. The overall fuel budget during the mission period is evaluated and compared. The design in this paper will provide technical support and reliable reference for future exoplanet exploration missions.