Typical Satellite Research Articles

Disentangling the efficient photocatalytic reduction of CO2 by a stable UiO-66-NH2/Cs2AgBiBr6 catalyst

The compelling global warming crisis as well as extraterrestrial artificial light synthesis craves photocatalytic reduction of CO2 into fuels and value-added chemicals, for which efficient and robust catalysts with high selectivity and conversion rate is a prerequisite but hitherto a rarity. Herein we create a lead-free double metal perovskite of Cs2AgBiBr6, coupling with mesoporous/microporous UiO-66-NH2 MOF to form type-II heterojunctions for efficient photocatalytic reduction of CO2 with a high CO selectivity of 95 % at an electron consumption rate of 33 μmol g−1 h−1 (13.4 μmol g−1 h−1 for CO and 0.72 μmol g−1 h−1 for CH4). Multilayered mesoporous MOF particles manifest higher catalytic activity than their microporous counterparts due to the highly open mesoporous channels and larger pore volume of the former. Femtosecond transient absorption in combination with in situ infrared spectroscopic measurements disentangle the underlying mechanism accounting for the high product selectivity: the ultrafast electron transfer of 12.3 ps from Cs2AgBiBr6 to UiO-66-NH2-2 enables efficient charge separation; primary *COOH intermediates and rapid CO desorption from Bi-based photocatalyst lead to dominant CO product. Moreover, the MOF crystals maintain stability after γ-rays irradiation equivalent of over 45-year accumulation in a typical earth orbit, hinting their promising potential in extraterrestrial artificial light synthesis.

Efficient disposal of low lunar orbiters on the lunar surface

Realistic numerical simulations are conducted to explore safe and efficient strategies for End-of-Life lunar spacecraft disposal on the lunar surface. Disposal from three different near-polar, low-altitude, and near-circular orbit types was analyzed to determine if impact locations that minimize the risk to protected regions of the lunar surface can be achieved consistently for low fuel costs using the Moon’s non-spherical gravity field. A total of 300,000 objects were propagated following retrograde disposal burns using a high-fidelity lunar trajectory model, and the disposal burn locations and magnitudes were compared against the resulting likelihoods of decay and lunar surface impact locations. The results identified disposal strategies that could achieve impact in safe locations for 10 m/s of ΔV or less for all orbit types, much lower than the ΔV cost to lower the perilune entirely to the lunar surface. A similar simulation-based methodology could be applied to operational lunar satellites to identify disposal strategies based on specific mission conditions. The results of this study support the development of safe and efficient End-of-Life disposal strategies that minimize the accumulation of debris in lunar orbit and extend the operational lifetimes of lunar missions.

Flexible Bridge-Conic Strategies for Moon-to-Moon Analytical Transfer Design

The multi-burn transfer framework based on the moon-to-moon analytical transfer method allows rapid patching of low-energy trajectories in the vicinity of different moons in a planetary system. However, the semimajor axis and eccentricity of intermediate arcs of one transfer mission are fixed in the existent multi-burn strategies. Additional propellant consumption is required to enable the transfers at all departure epochs, and a nonanalytical formulation still remains for transferring to spatial periodic orbits. To address these difficulties, new multi-burn strategies with variable intermediate arcs are proposed to meet the transfer conditions for different types of arrival orbits. Specifically, one or two intermediate arcs with one variable parameter are introduced and can be determined analytically. In numerical simulations, the proposed flexible bridge-conic strategies are applied to design transfers between libration point orbits in both the Jovian and Saturnian systems. Final results validate the effectiveness of the proposed strategies and indicate the important advantage in propellant saving compared with the existent multi-burn strategies.

Orbit–Orbit Interaction in Spatiotemporal Optical Vortex

While spin-orbit interaction has been extensively studied, few investigations have reported on the interaction between orbital angular momenta (OAMs). In this work, we study a new type of orbit–orbit coupling between the longitudinal OAM and the transverse OAM carried by a three-dimensional (3D) spatiotemporal optical vortex (STOV) in the process of tight focusing. The 3D STOV possesses orthogonal OAMs in the x–y, t–x, and y–t planes, and is preconditioned to overcome the spatiotemporal astigmatism effect. x, y, and t are the axes in the spatiotemporal domain. The corresponding focused wavepacket is calculated by employing the Debye diffraction theory, showing that a phase singularity ring is generated by the interactions among the transverse and longitudinal vortices in the highly confined STOV. The Fourier-transform decomposition of the Debye integral is employed to analyze the mechanism of the orbit–orbit interaction. This is the first revelation of coupling between the longitudinal OAM and the transverse OAM, paving the way for potential applications in optical trapping, laser machining, nonlinear light-matter interactions, and more.

LTSCD-YOLO: A Lightweight Algorithm for Detecting Typical Satellite Components Based on Improved YOLOv8

LTSCD-YOLO: A Lightweight Algorithm for Detecting Typical Satellite Components Based on Improved YOLOv8

Applying MBSE to Optimize Satellite and Payload Interfaces in Early Mission Phases

The use of model-based systems engineering (MBSE) has been increasingly explored recently in industries that require multi-discipline engineering coordination. In the European space industry, applying MBSE for the engineering of space systems has been an ongoing undertaking on many missions. In the following paper, the MBSE activities in CAMEO conducted during the A/B1 phases of a typical Earth observation satellite engineered by Airbus are discussed in detail in the form of a case study. The analyses shown are based around the modeling of the spacecraft electrical interfaces in CAMEO. This model was used to automate electrical interface control documents (EICDs) and enable the control of electrical interface development. These methodologies were further put in the context of Airbus’ satellite design processes to assess the benefits of an MBSE approach to the current electrical interface engineering procedure and the potential for the reuse of CAMEO models between satellite projects. The reduction in system engineering effort through the reuse of models to modularly create similar satellite systems for efficient concept evaluation and comparison is a clear benefit.

Characteristic Study of a Typical Satellite Solar Panel under Mechanical Vibrations.

As the most common energy source of spacecraft, photovoltaic (PV) power generation has become one of the hottest research fields. During the on-orbit operation of spacecraft, the influence of various uncertain factors and the unbalanced inertial force will make the solar PV wing vibrate and degrade its performance. In this study, we investigated the influence of mechanical vibration on the output characteristics of PV array systems. Specifically, we focused on a three-segment solar panel commonly found on satellites, analyzing both its dynamic response and electrical output characteristics under mechanical vibration using numerical simulation software. The correctness of the simulation model was partly confirmed by experiments. The results showed that the maximum output power of the selected solar panel was reduced by 5.53% and its fill factor exhibited a decline from the original value of 0.8031 to 0.7587, provided that the external load applied on the panel increased to 10 N/m2, i.e., the vibration frequency and the maximal deflection angle were 0.3754 Hz and 74.9871°, respectively. These findings highlight a significant decrease in the overall energy conversion efficiency of the solar panel when operating under vibration conditions.

Space-Based Passive Orbital Maneuver Detection Algorithm for High-Altitude Situational Awareness

Orbital maneuver detection for non-cooperative targets in space is a key task in space situational awareness. This study develops a passive maneuver detection algorithm using line-of-sight angles measured by a space-based optical sensor, especially for targets in high-altitude orbit. Emphasis is placed on constructing a new characterization for maneuvers as well as the corresponding detection method. First, the concept of relative angular momentum is introduced to characterize the orbital maneuver of the target quantitatively, and the sensitivity of the proposed characterization is analyzed mathematically. Second, a maneuver detection algorithm based on the new characterization is designed in which sliding windows and correlations are utilized to determine the mutation of the maneuver characterization. Subsequently, a numerical simulation system composed of error models, reference missions and trajectories, and computation models for estimating errors is established. Then, the proposed algorithm is verified through numerical simulations for both long-range and close-range targets. The results indicate that the proposed algorithm is effective. Additionally, the sensitivity of the proposed algorithm to the width of the sliding window, accuracy of the optical sensor, magnitude and number of maneuvers, and different relative orbit types is analyzed, and the sensitivity of the new characterization is verified using simulations.

Soil moisture alters the responses of alpine ecosystem productivity to environmental factors, especially VPD, on the Qinghai-Tibetan Plateau

Water availability, which can be represented by soil water content (SWC), plays a crucial role in plant growth and productivity across the cold and arid Qinghai-Tibetan Plateau. However, the indirect effects of SWC are less well understood, and a more comprehensive understanding of its regulating effects may enhance the recognition of its importance, as this factor is pivotal for accurately predicting the future response of alpine ecosystems to climate change. In this study, in situ eddy covariance observation data from typical alpine ecosystems and satellite data covering the Qinghai-Tibetan region were used to comprehensively reveal the effects of SWC on ecosystem productivity. The results indicated that SWC played an important role in regulating the responses of gross primary productivity (GPP) to other environmental factors over both time and space, especially in terms of the responses of GPP to vapor pressure deficit (VPD). The regulating effect can be summarized as follows: there was a specific SWC value (SWC = 0.24 m3 m−3 on the Qinghai-Tibetan Plateau) above which SWC was no longer the primary limiting factor. The responses of GPP to certain environmental factors shifted from negative to positive when the SWC increased above this value. The responses of GPP to VPD exhibited the highest sensitivity to the regulating effects of SWC, with a general response pattern found across different temporal and spatial scales. The findings revealed divergent responses of GPP to environmental factors under different SWC conditions and between arid and humid regions, emphasizing the importance of soil water conditions. These findings suggest that water conditions should be given primary consideration in global change studies.

Design of a Cislunar space navigation constellation based on special long-period orbits

This paper proposes a method for designing a navigation constellation in the Cislunar space. Firstly, the dynamic characteristics of the Cislunar space were analyzed. Northern Halo orbits and southern Halo orbits around L1 and L2 libration point are designed. Then, based on the invariant manifold theory, the homoclinic low-energy transfer trajectories of L1 Halo orbits and the low-energy heteroclinic transfer trajectories between L1 and L2 Halo orbits are provided respectively. Afterthat, two types of special long-period orbits are attained for the constellation design. Based on the geometric dilution of precision and the minimum number of visible satellites, design requirements for two parts are given. Next, two navigation constellation configurations are proposed. Lastly, simulations are conducted on the performance of two constellation configurations with different number of satellites. Compared to constellations in one orbit, constellations that configured in two orbits require fewer satellites to meet the design requirements. In different lunar transfer orbits, the performance of the dual orbit constellation was validated.

Asteroid Impact Hazard Warning from the Near-Earth Object Surveyor Mission

NASA’s Near-Earth Object Surveyor mission, scheduled for launch in 2027 September, is designed to detect and characterize at least two-thirds of the potentially hazardous asteroids with diameters larger than 140 m in a nominal 5 yr mission. We describe a model to estimate the survey performance using a faster approach than the time domain survey simulator described in Mainzer et al. (2023). This model is applied to explain how the completeness for 5 and 10 yr surveys varies with orbit type and asteroid size and to identify orbits with notably high or low likelihoods of detection. Size alone is an incomplete proxy for impact hazard, so for each asteroid orbit, we also calculate the associated hazard based on the impact velocity and the relative likelihood of impact. We then estimate how effective the mission will be at anticipating impacts as a function of impact energy, finding that a 5 yr mission will identify 87% of potential impacts larger than 100 Mt (Torino-9, “Regional Devastation”). For a 10 yr mission, this increases to 94%. We also show how the distribution of warning time varies with impact energy.

Poisson–Lie analogues of spin Sutherland models revisited

Some generalizations of spin Sutherland models descend from ‘master integrable systems’ living on Heisenberg doubles of compact semisimple Lie groups. The master systems represent Poisson–Lie counterparts of the systems of free motion modeled on the respective cotangent bundles and their reduction relies on taking quotient with respect to a suitable conjugation action of the compact Lie group. We present an enhanced exposition of the reductions and prove rigorously for the first time that the reduced systems possess the property of degenerate integrability on the dense open subset of the Poisson quotient space corresponding to the principal orbit type for the pertinent group action. After restriction to a smaller dense open subset, degenerate integrability on the generic symplectic leaves is demonstrated as well. The paper also contains a novel description of the reduced Poisson structure and a careful elaboration of the scaling limit whereby our reduced systems turn into the spin Sutherland models.

Orbital analysis of stars in the nuclear stellar disc of the Milky Way

Context. While orbital analysis studies were so far mainly focused on the Galactic halo, it is possible now to do these studies in the heavily obscured region close to the Galactic Centre. Aims. We aim to do a detailed orbital analysis of stars located in the nuclear stellar disc (NSD) of the Milky Way allowing us to trace the dynamical history of this structure. Methods. We integrated orbits of the observed stars in a non-axisymmetric potential. We used a Fourier transform to estimate the orbital frequencies. We compared two orbital classifications, one made by eye and the other with an algorithm, in order to identify the main orbital families. We also compared the Lyapunov and the frequency drift techniques to estimate the chaoticity of the orbits. Results. We identified several orbital families as chaotic, z-tube, x-tube, banana, fish, saucer, pretzel, 5:4, and 5:6 orbits. As expected for stars located in a NSD, the large majority of orbits are identified as z-tubes (or as a sub-family of z-tubes). Since the latter are parented by x2 orbits, this result supports the contribution of the bar (in which x2 orbits are dominant in the inner region) in the formation of the NSD. Moreover, most of the chaotic orbits are found to be contaminants from the bar or bulge which would confirm the predicted contamination from the most recent NSD models. Conclusions. Based on a detailed orbital analysis, we were able to classify orbits into various families, most of which are parented by x2-type orbits, which are dominant in the inner part of the bar.

Resonance response and chaotic analysis for an irrational pendulum system

We propose a novel rotating pendulum system with irrational nonlinearity, bi-stable phenomenon and quasi-zero stiffness characteristic, which bears a transition from standard double well dynamics to discontinuous double well dynamics by adjusting a geometric parameter. Nonlinear dynamical behaviors of the proposed irrational pendulum system subjected to viscus damping and periodic excitation are studied. To analytically demonstrate the primary resonance response for this perturbed irrational pendulum system, we introduce an approximate irrational system which is significant parallels with the original pendulum system from the perspective of qualitative analysis and quantitative calculation. Averaging method is applied to investigate the dynamic response of the perturbed irrational pendulum system with quasi-zero stiffness at origin. The effect of the internal and external parameters on the response curves are discussed. Numerical fitting technique and semi-analytical Melnikov method are used to detect the chaotic boundaries of the perturbed irrational pendulum system with two types of homoclinic orbits. Different types of periodic solutions and chaos are clarified in the perturbed irrational pendulum system by using numerical simulations. It is found that a class of chaos with oscillatory and rotational motions bears significant similarities to paroxysmal chaos due to sudden rotational motion and two chaotic motions formed by period-doubling bifurcation merge into one chaos.

Analysis of the Geodesic Motions of Massive Particles in Kerr–Sen–AdS4 Spacetime

We consider geodesic motions in Kerr–Sen–AdS4 spacetime. We obtain equations of motion for light rays and test particles. Using parametric diagrams, we show some regions where radial and latitudinal geodesic motions are allowed. We analyze the impact of parameters related to the dilatonic scalar on the orbit and find that it will result in more rich and complex orbital types.

Monte Carlo simulation of spacecraft breakup events in Low Lunar Orbit

Monte Carlo simulations of spacecraft breakup events in Low Lunar Orbit are conducted to study the behavior of artificial debris across all orbit types in this environment. 2000 breakup events at random initial states in lunar orbit are simulated, and the resulting nearly 500,000 particles are propagated for five years using a high-fidelity lunar trajectory model. Debris from a smaller sample of 200 breakup events is also propagated for ten years. Trends in the rate of decay of debris from lunar orbit are analyzed to investigate the longevity of debris in lunar orbit, and the locations of lunar surface impacts are plotted to determine if some regions of the Moon would be at greater risk than others from an orbital breakup event. Across all orbits, about 38% of the debris remained in lunar orbit after five years, and the longevity of debris was found to depend significantly on the pre-breakup perilune and inclination. Debris generally remained in lunar orbit for less time as the pre-breakup perilune decreased, although an average of 19% the debris remained in lunar orbit after five years even for pre-breakup perilune altitudes below 50 km. Debris was also found to be highly unstable in certain inclinations. The rates of decay across all orbit types tended to slow greatly after two years, suggesting that a portion of the debris can often remain in lunar orbit for at least a decade. Finally, clusters of lunar surface debris impacts were identified, which could have applications for lunar satellite disposal after mission completion. The results of this study provide novel insights into the consequences of lunar breakup events, helping support the development of debris mitigation recommendations for lunar orbit as international interest in exploration of the Moon grows.

Analysis of BDS inter-satellite link ranging performance

The Ka-band inter-satellite link (ISL) is a key technology of BeiDou Global Navigation Satellite System (BDS-3) that can improve the system performance. Based on 30 days of ISL observations, we analyze the BDS-3 ISL ranging performance and the related influencing factors, such as satellite manufacturer, satellite orbit type and link type. The fitting residuals of the ISL geometry-free observations are used to characterize the measurement noise, and the post-fit ISL residuals from precise orbit determination (POD) and precise clock estimation (PCE) are used to further validate the ranging performance. The fitting residuals follow a normal distribution, and the average root mean square (RMS) value for all 421 links is approximately 2.5 cm. The satellite manufacturers, China Academy of Space Technology (CAST) and Shanghai Engineering Center for Microsatellites (SECM), have an obvious impact on the ISL measurement noise. The RMS of the ISL fitting residuals for the links established by the two CAST satellites is only 1.45 cm, while it can reach 3.34 cm for the links established by the two SECM satellites. This correlation between ISL ranging performance and the satellite manufacturer is also found in the POD and PCE post-fit ISL residuals. The RMS of PCE residuals is about 3.1 cm, while the POD residuals are larger with the RMS of 5.5 cm due to the effect of orbital errors, especially for the Inclined Geosynchronous Orbit (IGSO) and Geostationary Orbit (GEO) satellites. Overall, the ranging accuracy of the BDS-3 ISL is better than 5 cm according to the above analyses. Furthermore, the BDS-3 satellite orbit and clock results are evaluated by internal consistency check and external comparison to analyze the application of ISL observations.

Stratification of the transverse momentum map

Given a Hamiltonian action of a proper symplectic groupoid (for instance, a Hamiltonian action of a compact Lie group), we show that the transverse momentum map admits a natural constant rank stratification. To this end, we construct a refinement of the canonical stratification associated to the Lie groupoid action (the orbit type stratification, in the case of a Hamiltonian Lie group action) that seems not to have appeared before, even in the literature on Hamiltonian Lie group actions. This refinement turns out to be compatible with the Poisson geometry of the Hamiltonian action: it is a Poisson stratification of the orbit space, each stratum of which is a regular Poisson manifold that admits a natural proper symplectic groupoid integrating it. The main tools in our proofs (which we believe could be of independent interest) are a version of the Marle–Guillemin–Sternberg normal form theorem for Hamiltonian actions of proper symplectic groupoids and a notion of equivalence between Hamiltonian actions of symplectic groupoids, closely related to Morita equivalence between symplectic groupoids.

Improved SSA-Based GRU Neural Network for BDS-3 Satellite Clock Bias Forecasting.

Satellite clock error is a key factor affecting the positioning accuracy of a global navigation satellite system (GNSS). In this paper, we use a gated recurrent unit (GRU) neural network to construct a satellite clock bias forecasting model for the BDS-3 navigation system. In order to further improve the prediction accuracy and stability of the GRU, this paper proposes a satellite clock bias forecasting model, termed ITSSA-GRU, which combines the improved sparrow search algorithm (SSA) and the GRU, avoiding the problems of GRU's sensitivity to hyperparameters and its tendency to fall into local optimal solutions. The model improves the initialization population phase of the SSA by introducing iterative chaotic mapping and adopts an iterative update strategy based on t-step optimization to enhance the optimization ability of the SSA. Five models, namely, ITSSA-GRU, SSA-GRU, GRU, LSTM, and GM(1,1), are used to forecast the satellite clock bias data in three different types of orbits of the BDS-3 system: MEO, IGSO, and GEO. The experimental results show that, as compared with the other four models, the ITSSA-GRU model has a stronger generalization ability and forecasting effect in the clock bias forecasting of all three types of satellites. Therefore, the ITSSA-GRU model can provide a new means of improving the accuracy of navigation satellite clock bias forecasting to meet the needs of high-precision positioning.

Quasi-periodic orbits of small solar sails with time-varying attitude around Earth–Moon libration points

This paper proposes new quasi-periodic orbits around Earth–Moon collinear libration points using solar sails. By including the time-varying sail orientation in the linearized equations of motion for the circular restricted three-body problem (CR3BP), four types of quasi-periodic orbits (two types around L1 and two types around L2) were formulated. Among them, one type of orbit around L2 realizes a considerably small geometry variation while ensuring visibility from the Earth if (and only if) the sail acceleration due to solar radiation pressure is approximately of a certain magnitude, which is much smaller than that assumed in several previous studies. This means that only small solar sails can remain in the vicinity of L2 for a long time without propellant consumption. The orbits designed in the linearized CR3BP can be translated into nonlinear CR3BP and high-fidelity ephemeris models without losing geometrical characteristics. In this study, new quasi-periodic orbits are formulated, and their characteristics are discussed. Furthermore, their extendibility to higher-fidelity dynamic models was verified using numerical examples.