Satellite Research Articles

Dynamical Model of Rotation and Orbital Coupling for Deimos

This paper introduces a novel dynamical model, building upon the existing dynamical model for Deimos in the current numerical ephemerides, which only encompasses the simple libration effects of Deimos. The study comprehensively incorporates the rotational dynamics of Deimos influenced by the torque exerted by the major celestial bodies (Mars, the Sun) in the solar system within the inertial space. Consequently, a full dynamical model is formulated to account for the complete coupling between the rotation and orbit of Deimos. Simultaneously, employing precision orbit determination methods used for artificial satellites, we develop an adjustment model for fitting data to the complete model. The 12-order Adams–Bashforth–Moulton (ABM) integration algorithm is employed to synchronously integrate the 12 state variables of the full model to obtain the orbit of Deimos.The difference in the orbits obtained by integrating the full model over a period of 10 years and those obtained by the simplified model is at the order of 10 km. After precise orbit determination, this difference decreases to below 100 m, so numerical simulation results indicate that the full dynamical model and adjustment model are stable and reliable. Simultaneously, the integration of the Deimos third-order gravity field in the full model over a 10-year period induces only meter-level positional changes. This suggests that when constructing the complete model, the utilization of a second-order gravity field alone is sufficient. Compared to the simple model, the polar axis of Deimos in the inertial space exhibits a more complex oscillation in the full model. Additionally, the full model calculates that the minimum moment of inertia principal axis of Phobos has an amplitude of approximately 0.5 degrees in the longitude direction and does not exceed 2 degrees in the latitude direction. This work further advances the current dynamical model for Deimos and establishes the foundational model for the generation of a new set of precise numerical ephemerides for Deimos.

Overview of Fault Zones Based on Remote Sensing Data as Contribution to the Safety of Infrastructure and Land Use in Southern Egypt

Part of a requisite for natural hazard awareness and damage prevention in Egypt is the detailed monitoring of surface fault zones. The inventory of active faults and their risk assessment is an essential contribution to the safety of settlements, land use and infrastructure (railroads, highways, pipelines) and to damage prevention. Thus, this study aims to contribute to the detection, inventory, and documentation of fault zones. Surface faulting hazard assessment considers any surface consequences caused by surface near faults such as abrupt horizontal and vertical displacements and rotations, or mass movements after stronger earthquakes. Long-term, aseismic, slow-creeping movements along fault zones have to be considered as well. Southern Egypt offers unique and optimal conditions for the research of fault zones and their different structural expressions and conditions because of the dry desert climate conditions and relatively low human influence on the landscape in extended areas, especially for the investigation of different types of faults, their interactions with each other and the outcropping rocks, and fault-related deformation structures. Volcanic activity has been influenced in the geologic past often by larger fault zones as dike intrusions, volcanic cones and plugs or craters occur concentrated along these zones of weakness facilitating the uprise of magma. Larger fault zones are crossing reservoir areas. Surface water intrusions into deep-seated faults have played a role in triggering earthquake swarms in the reservoir areas during the last decades. Mapping of active faults is not only an important but also a cost-intense task when carried out in the field or when using geodetic and geophysical data. In the scope of this study, fault detection was carried out based on different open-source satellite data (Landsat 8 and 9, Sentinel 2 optical data, Sentinel 1 and ALOSPASAR radar data, and Google Earth and Bing Map high-resolution satellite images) from the southern part of Egypt. Faults were digitized using ArcGIS and QGIS software. An inventory of fault-related structural features (depressions, ridges, rotation structures, etc.) and rift zones was elaborated based on remote sensing data. An overview of different types of faults and their related structures as well as their interactions with their host rock conditions could be achieved. By merging the inventory results with infrastructural and land use data, critical areas with potential damage risk were pointed out.

Фотометрические наблюдения и моделирование формы космического мусора на средневысотных орбитах

The circular medium Earth orbits with a period of about half a day in the inclination range from 50° to 70° are used by various global navigation satellite systems (GNSS), such as GLONASS, GPS, Beidou, Galileo. GNSS operating orbits are one of the important areas in near-Earth space. The information about the space debris (SD) existing in this region and its characteristics is important for risk assessments and mitigation. We report the results of photometrical observations of SD objects in the vicinity of GNSS orbits obtained with the 1.6-meter AZT-33IK telescope of ISTP SB RAS Sayan Solar Observatory in 2018–2023. We show how SD objects existing in this region are distributed relative to GNSS objects. We derive time and phase dependences of the apparent brightness of all measured SD objects. Folded light curves are constructed, rotation periods and their dynamics are determined. The results of modeling the light curve inherent for several SD objects from the GNSS orbital are presented. We suggest a possible space object shape and parameters of proper rotation, which correspond to the observed light curve.

Cooperative Caching and Resource Allocation in Integrated Satellite–Terrestrial Networks

Due to the rapid development of low earth orbit satellite constellations, e.g., Starlink, OneWeb, etc., integrated satellite-terrestrial networks have been viewed as a promising paradigm to globally provide satellite internet services for users. However, when the contents from ground data centers are provided for users by satellite networks, there will be high capital expenditures in terms of communication delay and bandwidth usage. To this end, in this paper, a cooperative-caching and resource-allocation problem is investigated in integrated satellite–terrestrial networks. Popular contents, which are cached on satellites and ground data centers, can be accessed via inter-satellite and satellite–terrestrial networks in a cooperative way. The optimization problem is formulated to jointly minimize the deployment costs of storage resource usage and network bandwidth consumption. A cooperative caching and resource allocation (CCRA) algorithm based on a neighborhood search is proposed to address the problem. The simulation results demonstrate that the proposed CCRA algorithm outperforms Greedy and BFS in reducing the deployment costs.

Berthing proximity maneuvers and trajectory planning of a space manipulator via Kane’s formulation

On-orbit servicing is one of the most challenging tasks of the recent space era. Space Manipulator Systems (SMS) can represent viable technological solutions for several space operations, such as in-situ refueling, repairing of operating spacecraft, or debris grappling. Regardless of the specific task, SMS must approach the target object and then establish a physical connection with it using a single or more robotic arms. This work considers a space vehicle equipped with a pair of two-link robotic arms, with the intent of efficiently designing and simulating the overall spacecraft dynamics until contact takes place. The links that compose each arm are modeled as rigid bodies, assuming relatively slow dynamics. Instead, flexibility is introduced in the model of the rotary joints. The overall dynamics is investigated using Kane’s methodology, which is general, highly systematic, and joins the advantages of both the Newton/Euler and the Lagrange formulation. Both SMS and the target, assumed as noncooperative, are placed in low Earth orbit, in close proximity. Trajectory planning of the robotic arm is investigated, while considering the effect of the arm motion on the overall attitude dynamics. Precise attitude maneuvering is mandatory in order that grappling be successfully completed. To do this, a quaternion-based, globally stable attitude feedback law is designed, implemented, and tested. Actuation is demanded to an arrangement of control momentum gyroscopes. These devices are modeled with the inclusion of gyroscopic coupling effects, and are driven by means of suitable steering laws, for the purpose of pursuing the desired attitude control action. Accurate modeling of SMS, with also the inclusion of disturbances due to joint flexibility, in conjunction with the use of suitable feedback attitude control and steering laws for both the robotic arms and the actuation devices, allows obtaining the desired variables, i.e. (i) the motor torques (for steering both the joints and the attitude devices) and (ii) the constraint actions (forces and torques). A Monte Carlo analysis points out effectiveness of the control architecture proposed in this study in the challenging mission scenario of interest.

Photometrical observations and shape modeling of space debris in medium Earth orbits

The circular medium Earth orbits with a period of about half a day in the inclination range from 50° to 70° are used by various global navigation satellite systems (GNSS), such as GLONASS, GPS, Beidou, Galileo. GNSS operating orbits are one of the important areas in near-Earth space. The information about the space debris (SD) existing in this region and its characteristics is important for risk assessments and mitigation. We report the results of photometrical observations of SD objects in the vicinity of GNSS orbits obtained with the 1.6-meter AZT-33IK telescope of ISTP SB RAS Sayan Solar Observatory in 2018–2023. We show how SD objects existing in this region are distributed relative to GNSS objects. We derive time and phase dependences of the apparent brightness of all measured SD objects. Folded light curves are constructed, rotation periods and their dynamics are determined. The results of modeling the light curve inherent for several SD objects from the GNSS orbital are presented. We suggest a possible space object shape and parameters of proper rotation, which correspond to the observed light curve.

TO THE 60TH ANNIVERSARY OF THE DEPARTMENT OF EARTH SCIENCES OF THE NATIONAL ACADEMY OF SCIENCES OF UKRAINE

In the second part of the article, the main historical events in terms of dates, facts and personalities of the formation and development of the institutions of the Department of Earth and Space Sciences of the Academy of Sciences of the Ukrainian SSR from its foundation in 1963 to Ukraine’s independence in 1991 are listed in chronological order. The course of events related to name changes is given: Department of Earth and Space Sciences (1963–1972), Department of Earth Sciences (1972–1980), Department of Geology, Geophysics and Geochemistry (1980–1983) and Department of Earth Sciences (1983–1991). Considerable attention is paid to the significant contribution of the specialists of the Department of Earth Sciences of the Academy of Sciences of the Ukrainian SSR in eliminating the consequences of the largest technogenic and environmental disaster that occurred on April 26, 1986 at the Chornobyl nuclear power plant. It is considered the most important achievements of the institutions of the Department of Earth Sciences of the Academy of Sciences of the Ukrainian SSR in the period of formation and active development. In particular, scientific substantiation of the search for industrial oil and gas accumulations in the crystalline foundation of the sedimentary basins of Ukraine, volcanic and volcanogenic-sedimentary rocks of Transcarpathia and the Dnipro region, in the zones of active water exchange on the regional monoclines of Precarpathia, the Black Sea region. The doctrine of the formation of deep fault structures has been developed, and a technique has been developed for forecasting of combined traps of hydrocarbon accumulations in deep-seated Devonian and Carboniferous horizons of the Dnipro-Donetsk Basin. Significant results were obtained regarding the geological structure of the earth’s crust and the upper mantle of the lithosphere within the framework of international projects during regional seismic research within limits of Ukraine, Southeast Europe and India. The general regularities of the structure are established for various geostructures: shields, platforms, depressions, transition zones from continents to oceans, deep-sea depressions, structures of the ocean floor. The theoretical principles, methods and technical means of remote ocean research using artificial Earth satellites were developed, and the country’s first system for collecting, transmitting and processing information about the ocean’s physical fields was created. This is a kind of report of the most significant events and facts from the life of the Department of Earth Sciences of the National Academy of Sciences of Ukraine and personal information and scientific achievements of the members of the Academy elected in the considered period.

Orbital Facility Location Problem for Satellite Constellation Servicing Depots

This work proposes an adaptation of the facility location problem for the optimal placement of on-orbit servicing depots for satellite constellations in high-altitude orbit. The high-altitude regime, such as medium Earth orbit, is a unique dynamic environment where low-thrust propulsion systems can provide the necessary thrust to conduct plane-change maneuvers between the various orbital planes of the constellation. As such, on-orbit servicing architectures involving servicer spacecraft that conduct roundtrips between servicing depots and the client satellites of the constellation may be conceived. To this end, a new orbital facility location problem formulation is proposed based on binary linear programming, in which the costs of operating and allocating the facility(ies) to satellites are optimized in terms of the sum of the effective mass to low Earth orbit (EMLEO). The low-thrust transfers between the facilities and the clients are computed using a parallel implementation of a Lyapunov feedback controller. The total launch cost of the depot, along with its servicers, propellant, and payload, is taken into account as the cost to establish a given depot. The proposed approach is applied to designing an on-orbit servicing depot architecture for the Galileo and the GPS constellations.

Concept and Feasibility Analysis of the Alba Cubesat Mission

AlbaSat is a 2-Unit CubeSat which is being developed by a student team at the University of Padova. The Alba project aims to design, build, test, launch, and operate the first student CubeSat of the University of Padova, featuring four different payloads. The first goal is to collect data regarding the debris environment in Low Earth Orbit, the second goal is the study of the satellite vibrations, the third one is about CubeSat attitude determination through laser ranging technology, and the fourth goal concerns satellite laser and quantum communication. The Alba CubeSat mission has been selected by the European Space Agency to join the Fly Your Satellite! Design Booster program in December 2022. This paper presents the feasibility study of the Alba CubeSat mission reproduced in the framework of the “Space Systems Laboratory” class of Master of Science in Aerospace Engineering at the University of Padova. In the beginning, a mission requirements definition was conducted. After that, the mission feasibility was considered, with preliminary requirements verification to assess the ability of the spacecraft to survive the space environment, including compliance with Debris Mitigation Guidelines, ground station visibility and minimum operative lifetime evaluation. The Alba mission sets a base for a better understanding of the space environment and its interaction with nanosatellites, and an improvement of the accuracy of debris models. Furthermore, this paper, describing the educational experience and the results achieved, will provide a useful example for future students’ studies on CubeSat mission design.

Research on space power supply utilizing series-parallel techniques

In the realm of space exploration, maintaining a stable and reliable power supply is crucial for the sustained and uninterrupted operation of artificial satellites. However, the unpredictable and often harsh space environment necessitates a redundant design for space power supplies to enhance overall reliability. In light of this, this paper introduces a full-bridge converter employing a series-parallel topology, which augments input voltage redundancy through a combination of serial and parallel connections. Furthermore, a dual-loop Proportional-Integral (PI) control feedback system has been devised, along with a comprehensive analysis of system stability to ensure the optimal performance of both output voltage and current. To validate the efficacy of the series-parallel topology and the feedback system, a complete circuit is constructed, and extensive simulations are carried out under diverse conditions.

Narrowband Internet of Things via Low Earth Orbit Satellite Networks: An Efficient Coverage Enhancement Mechanism Based on Stochastic Geometry Approach.

With the development of IoT technology and 5G massive machine-type communication, the 3GPP standardization body considered as viable the integration of Narrowband Internet of Things (NB-IoT) in low Earth orbit (LEO) satellite-based architectures. However, the presence of the LEO satellite channel comes up with new challenges for the NB-IoT random access procedures and coverage enhancement mechanism. In this paper, an Adaptive Coverage Enhancement (ACE) method is proposed to meet the requirement of random access parameter configurations for diverse applications. Based on stochastic geometry theory, an expression of random access channel (RACH) success probability is derived for LEO satellite-based NB-IoT networks. On the basis of a power consumption model of the NB-IoT terminal, a multi-objective optimization problem is formulated to trade-off RACH success probability and power consumption. To solve this multi-objective optimization problem, we employ the Non-dominated Sorting Genetic Algorithms-II (NSGA-II) method to obtain the Pareto-front solution set. According to different application requirements, we also design a random access parameter configuration method to minimize the power consumption under the constraints of RACH success probability requirements. Simulation results show that the maximum number of repetitions and back-off window size have a great influence on the system performance and their value ranges should be set within [4, 18] and [0, 2048]. The power consumption of coverage enhancement with ACE is about 58% lower than that of the 3GPP proposed model. All this research together provides good reference for the scale deployment of NB-IoT in LEO satellite networks.

Performance analysis of multi-hop low earth orbit satellite network over mixed RF/FSO links

Low earth orbit satellite (LEOS) communication has emerged as a promising technology to achieve global coverage, while further reducing the end-to-end latency by establishing communication link between LEOSs. In this paper, we analyze the performance of multi-hop LEOS network in terms of bit error rate (BER) and outage probability over mixed radio frequency (RF)/free space optical (FSO) links where RF link is used for the link between ground terminal and LEOS and FSO link is used for establishing inter-satellite links (ISLs). The derived closed-form results are confirmed via Monte Carlo simulations and we show the effect of the number of satellite hops on outage probability and average BER performance by comparing scenarios both with and without ISLs.

Novel statistical method for data drift detection in satellite telemetry

SummaryAutonomy is becoming a prime requirement for satellite mission control operations. Data‐driven methods like Machine Learning models are playing a key role in bringing in autonomy. Health keeping data from satellite telemetry is a key ingredient in these data‐driven methods. In real‐world satellite operations, the health‐keeping telemetry data gradually drifts due to adverse space weather effects and wear and tear of electronic and mechanical components. The key question that arises is how to detect and quantify the data drift which is generally a gradual phenomenon. This paper discusses a novel statistical method for detecting data drift occurring in satellite telemetry. For the purpose of experimental work in this paper, an actual telemetry data set of the BUS CURRENT sensor which is part of the Electrical Power System of a Low Earth Orbit Satellite was considered. Data drift detection test was carried out using this sensor data using the developed novel statistical method and with Kolmogorov Smirnov test which is a probabilistic method. Both results are analysed and compared. Thereafter novel statical method was used to check its efficacy using a synthetic data set with induced drift.

Time transfer over 113 km free space laser communication channel.

The space time frequency transfer plays a crucial role in applications such as space optical clock networks, navigation, satellite ranging, and space quantum communication. Here, we propose a high-precision space time frequency transfer and time synchronization scheme based on a simple intensity modulation/direct detection (IM/DD) laser communication system, which occupies a communication bandwidth of approximately 0.2%. Furthermore, utilizing an optical-frequency comb time frequency transfer system as an out-of-loop reference, experimental verification was conducted on a 113 km horizontal atmospheric link, with a long-term stability approximately 8.3 × 10-16 over a duration of 7800 seconds. Over an 11-hour period, the peak-to-peak wander is approximately 100 ps. Our work establishes the foundation of the time frequency transfer, based on the space laser communication channel, for future ground-to-space and inter-satellite links.

High accuracy ranging for space debris with spaceborne single photon Lidar.

The increasing risk posed by space debris highlights the need for accurate localization techniques. Spaceborne single photon Lidar (SSPL) offers a promising solution, overcoming the limitations of traditional ground-based systems by providing expansive coverage and superior maneuverability without being hindered by weather, time, or geographic constraints. This study introduces a novel approach leveraging non-parametric Bayesian inference and the Dirichlet process mixture model (DPMM) to accurately determine the distance of space debris in low Earth orbit (LEO), where debris exhibits nonlinear, high dynamic motion characteristics. By integrating extended Kalman filtering (EKF) for range gating, our method captures the temporal distribution of reflected photons, employing Markov chain Monte Carlo (MCMC) for iterative solutions. Experimental outcomes demonstrate our method's superior accuracy over conventional statistical techniques, establishing a clear correlation between radial absolute velocity and ranging error, thus significantly enhancing monostatic space debris localization.

Manipulating Hetero-Nanowire Films for Flexible and Multifunctional Thermoelectric Devices.

Flexible thermoelectric devices hold significant promise in wearable electronics owing to their capacity for green energy generation, temperature sensing, and comfortable wear. However, the simultaneous achievement of excellent multifunctional sensing and power generation poses a challenge in these devices. Here, ordered tellurium-based hetero-nanowire films are designed for flexible and multifunctional thermoelectric devices by optimizing the Seebeck coefficient and power factor. The obtained devices can efficiently detect both object and environment temperature, thermal conductivity, heat proximity, and airflow. In addition, combining the thermoelectric units with radiative cooling materials exhibits remarkable thermal management capabilities, preventing device overheating and avoiding degradation in power generation. Impressively, this multifunctional electronics exhibits excellent resistance in extreme low earth orbit environments. The fabrication of such thermoelectric devices provides innovative insights into multimodal sensing and energy harvesting.

Magnetic Attitude Control Scheme for Drag Sail Deorbiting with Limited Sensors

As concerns over space debris in the Low Earth orbit (LEO) intensify, deorbit strategies for small satellites becomes evident because many lack an effective deorbit mechanism. After successfully demonstrating their effectiveness in flight tests, aerodynamic drag sails emerge as a superior deorbit solution, significantly reducing the time required for deorbiting. To maximize the aerodynamic drag, it is crucial to maintain the drag sail perpendicular to the atmospheric flow. This becomes especially challenging with the potential threat of sensor failure. This paper introduces a magnetic control scheme for deorbiting using drag sails. Relying solely on magnetometers as sensors, the control scheme uses magnetorquers, bias momentum wheels, and an onboard geomagnetic field model to keep the sail perpendicular to the satellite’s velocity. Furthermore, a backup control scheme that does not require the onboard geomagnetic field model is proposed. This control scheme uses magnetometers in conjunction with just another common small satellite sensor, such as the GPS, gyroscopes, or sun sensors as sensors. A stability criterion, based on a linearized analytical model, validates the feasibility of this backup control scheme. Numerical simulations confirm the efficacy of both control schemes. Both schemes reduce the deorbit time by approximately 40% compared to the uncontrolled satellite deorbiting.

Neural Network-Based Formation Flying Using Aerodynamic Forces via Variable Shape Function

Conventional formation flying Earth-orbiting satellites control their orbits to perform their missions using thrusters, but the amount of propellant loaded into a satellite is limited. Therefore, the use of aerodynamic forces for orbit control has been attracting attention, particularly in low Earth orbit. The orbit control can be achieved by appropriately changing the state of satellite, such as attitude and shape, to meet the aerodynamic requirements. In modeling the relationship between satellite state and aerodynamic forces, conventional methods ignore the shielding caused by the nonconvexity of the satellite’s appearance. Ignoring the shielding creates a gap between the modeled and the real aerodynamic forces, resulting in poor control performance. To solve this problem, we propose an aerodynamic force modeling method that incorporates a neural network to estimate the shielding. We train the neural network using data from an aerodynamics simulator. The optimal state that not only generates the required aerodynamic forces but also improves controllability under various mechanical constraints is obtained by solving an optimization problem that incorporates the proposed aerodynamic model. We conduct numerical simulations for establishing and maintaining general circular orbit formations. The results show convergence and continuous stable control of the deputy satellite to the ideal orbit.

Effect of satellite availability and time delay of corrections on position accuracy of differential NavIC

Abstract The position accuracy of standalone Navigation with Indian Constellation (NavIC) may not be met for certain applications like civil aviation. To improve the position accuracy of the user receiver, the technique used is Differential NavIC, which makes use of Differential corrections. The position accuracy of the user receiver also depends on the satellite availability (i.e. number of satellites available at a certain time instant to estimate the user position) and delay in transmission of differential corrections. In this article, the analysis of differential NavIC using different numbers of visible satellites (satellite availability) and different time delays for transmission of corrections is carried out. For this analysis, three cases are considered, Case I is when all (six) NavIC satellites are visible, Case II is when five satellites (3 Geosynchronous Orbit (GSO) and 2 Geostationary Earth Orbit (GEO)) are visible, and Case III is when five satellites (3 GEO and 2 GSO) are visible. The comparative analysis for these three cases is carried out with respect to the position accuracy parameters and Geometric Dilution of Precision. It is observed that, with the satellite availability in case I and case III, the user receiver accuracy is approximately the same. In case III, the accuracy of the user receiver (3.08 m) is similar to the accuracy (3.09 m) in case I. For time delay in transmission of corrections, different time delays (0, 5, 10, 20, …, 300 s) are considered to observe the effect on the positional accuracy of the user receiver. Due to the increase in this time delay, there is a significant degradation in the user receiver position accuracy of differential NavIC.

Two-stage estimator for the complete inertia tensor of uncooperative debris on CubeSat based Active Debris Removal missions

The threat of debris collisions in Low Earth Orbit (LEO) has driven many researchers to develop Active Debris Removal (ADR) missions to manage large debris in LEO. A modern method of capturing debris with a non-rigid tether has been a recent research focus because of difficult post capture dynamics associated with controlling an uncooperative debris through a tether. To facilitate these control schemes, this paper proposes a new two-stage inertia estimator that estimates all principal and products of inertia for an uncooperative space debris using LiDAR and tether force measurements made on-board a CubeSat sized chaser satellite. The method proposed in this work estimates the debris center of mass with a novel pseudo measurement Kalman Filter so that the full inertia tensor can be subsequently estimated using an additional iterative parameter identification algorithm. In addition, the paper achieves online inertia estimation without assuming the tether connection point on the debris by approximating its location using tether tension measurements. The proposed control and estimation scheme is shown in this paper to estimate the full debris inertia tensor even with frequent tether slackness. Two simulation scenarios are presented in this paper, one where the connection point of the tether on the debris is approximated using noiseless measurements of tether tension, and a second where the location of the tether connection point is approximated using noisy measurements of tether tension. For the simulation conditions used in this research, it is shown that the proposed two-stage estimator (TSE) is successful for both cases that the debris is inertially asymmetrical and tri-inertial with non-zero products of inertia.