Satellite Services Research Articles

Dynamic Network Resource Autonomy Management and Task Scheduling Method

Satellite network resource management and scheduling technology are significant to constructing integrated information networks in heaven and earth. The difficulty in realizing this technology lies in improving resource utilization efficiency while ensuring the service quality of satellites and efficiently coordinating complex satellite network systems and services. This paper proposes a model, A Dynamic task scheduling method based on a UNified resource Management architecture(DUNM), based on the designed resource management architecture supported by dynamic scheduling algorithms to address the problems of low resource utilization, resource allocation, and task completion rate. First, with sufficient resources, the task execution time to complete a task is calculated based on the number of resources, task transmission time, task waiting time, etc. Secondly, based on the tasks assigned to satellites, the execution time of all functions with different transmission rates of communication links between satellites is calculated, and the total sum of all time consumption is analyzed. Finally, after simulation experiments and comparison with various baseline algorithms, about a 40% reduction in time to complete scheduled tasks and an almost 25% reduction in the average cost to finish a scheduling task, our method has higher scheduling efficiency and lower task completion revenue. It also guarantees a higher task completion rate while completing the tasks. Our approach attained a nearly 100% completion rate for scheduling tasks, which means that our algorithm can achieve the scheduling tasks faster and at high task revenue, thus improving the efficiency and economic efficiency of the whole system. Therefore, it validates the advantages of our method, such as high efficiency and high revenue.

Storm Time Electrified MSTIDs Observed Over Mid‐Latitude North America

AbstractMedium‐scale Traveling Ionospheric Disturbances (MSTIDs) are prominent and ubiquitous features of the mid‐latitude ionosphere, and are observed in Super Dual Auroral Radar Network (SuperDARN) and high‐resolution Global Navigational Satellite Service (GNSS) Total Electron Content (TEC) data. The mechanisms driving these MSTIDs are an open area of research, especially during geomagnetic storms. Previous studies have demonstrated that nightside MSTIDs are associated with an electrodynamic instability mechanism like Perkins, especially during geomagnetically quiet conditions. However, dayside MSTIDs are often associated with atmospheric gravity waves. Very few studies have analyzed the mechanisms driving MSTIDs during strong geomagnetic storms at mid‐latitudes. In this study, we present mid‐latitude MSTIDs observed in de‐trended GNSS TEC data and SuperDARN radars over the North American sector, during a geomagnetic storm (peak Kp reaching 9) on 7–8 September 2017. In SuperDARN, MSTIDs were observed in ionospheric backscatter with Line of Sight (LOS) velocities exceeding 800 m/s. Additionally, radar LOS velocities oscillated with amplitudes reaching ±500 m/s as the MSTIDs passed through the fields‐of‐view. In detrended TEC, these MSTIDs produced perturbations reaching ∼50 percent of background TEC magnitude. The MSTIDs were observed to propagate in the westward/south‐westward direction with a time period of ∼15 min. Projecting de‐trended GNSS TEC data along SuperDARN beams showed that enhancements in TEC were correlated with enhancements in SuperDARN SNR and positive LOS velocities. Finally, SuperDARN LOS velocities systematically switched polarities between the crests and the troughs of the MSTIDs, indicating the presence of polarization electric fields and an electrodynamic instability process during these MSTIDs.

Radiation Aspect of Two Orbit Inclination Options of the Russian Orbital Service Station

The contribution to the effective dose from cosmic radiation of the Earth’s radiation belts, galactic cosmic rays, and solar proton events for astronauts located in the large-diameter working compartment of the service module of the ISS is considered. It is shown that for quasi-stationary sources of cosmic radiation, a change in the orbital inclination of 51.6° by 97.0° does not lead to significant variations in the average daily effective dose rate. When considering the contribution to the effective dose from solar-flare protons, the dose load on astronauts can increase by ten or more times.

A joint strategy for service deployment and task offloading in satellite–terrestrial IoT

In recent years, low earth orbit satellite constellations, which are an important component of 6G, have been considered as a potential solution to achieve seamless network services for remote areas. Service deployment based on network function virtualization (NFV) has become an essential trend among satellite networks to enable flexible network services. However, current satellite–terrestrial IoT task offloading schemes rarely consider NFV-based satellite service deployment, which limits the performance of satellite networks. In this study, we address this problem by proposing an optimization problem that jointly considers service deployment and task offloading. To solve such a problem with many coupling decision variables, we decouple the problem using a two-stage approach. We propose a deep reinforcement learning-based service deployment policy to solve the service deployment subproblem and an alternating direction multiplier method-based distributed approach to solve the task offloading subproblem, which with the aim of minimizing the task latency and energy consumption of IoT devices. Simulation experiments demonstrate that our scheme can obtain near-optimal solution and can be adapted to large-scale satellite–terrestrial IoT network scenarios.

Retrieval dynamics and control for approach of tethered on-orbit service satellite

Approach and docking with space tether system has the advantages of less system complexity and lower cost compared with conventional rendezvous and docking which are usually essential operations in on-orbit service of spacecraft. This paper deals with the relative dynamics and control of the tethered on-orbit service satellite for the process of approach and docking by retrieving tether. Considering the system safety, it is necessary to keep the pitch angle constant or it varying in a small range during the approach. Therefore, we propose a control law for tether retrieval. Specifically, the relative dynamics equations are established to analyze the effects of orbit eccentricity, orbit altitude, and tether length rate on the system dynamics as well as investigate the property of pitch motion. Then the retrieval control law with constant pitch angle constraint is proposed using the dynamic inverse method based on the dynamics analyses. We further discuss the feasible region of orbit eccentricity and constant pitch angle for the control law to retrieve the tether. The numerical simulation experiments show that the proposed law can realize stable retrieval while maintaining a constant pitch angle.

Satellite Network Transmission of Cooperative Relay Superimposed Signal Reconstructed in Spatial Dimension

In order to save frequency resources, a new remote sensing satellite service can gradually adopt relay cooperation transmission to realize the same frequency and common channel transmission of multiple data. To solve the problem of mutual interference between messages, this study proposes a universal model of relay cooperative channel transmission, and the separation mechanism of heterogeneous signals for simultaneous unicast and multicast transmission is also studied. In this study, a signal space is used to reconstruct the degrees of freedom, and an orthogonalized spatial alignment direction is designed to obtain the equivalent parallel transmission channel. We also propose a constellation point remapping scheme under the optimal constraint of spatial separation of transmission signals. Furthermore, we merge constellation points to solve the problem of fuzzy mapping of physical layer network coding. The simulation results show that the co-channel transmission with interference suppression can be realized when the equivalent degrees of freedom of the signal intersection subspace is not less than dpK(K−1)+dcK. The Euclidean distance between constellation points is increased by constructing orthogonal signal spatial alignment directions, which brings an additional BER performance gain of 2 dB. If the signal alignment direction and channel quality are jointly designed, the transmission quality can be further improved.

Simulation of the Earth’s radio-leakage from mobile towers as seen from selected nearby stellar systems

ABSTRACT Mobile communication towers represent a relatively new but growing contributor to the total radio-leakage associated with planet Earth. We investigate the overall power contribution of mobile communication towers to the Earth’s radio leakage budget, as seen from a selection of different nearby stellar systems. We created a model of this leakage using publicly available data of mobile tower locations. The model grids the surface of the planet into small, computationally manageable regions, assuming a simple integrated transmission pattern for the mobile antennas. In this model, these mobile tower regions rise and set as the Earth rotates. In this way, a dynamic power spectrum of the Earth was determined, summed over all cellular frequency bands. We calculated this dynamic power spectrum from three different viewing points – HD 95735, Barnard’s star, and Alpha Centauri A. Our preliminary results demonstrate that the peak power leaking into space from mobile towers is ∼4GW. This is associated with Long Term Evolution (LTE) mobile tower technology emanating from the East Coast of China as viewed from HD 95735. We demonstrate that the mobile tower leakage is periodic, direction dependent, and could not currently be detected by a nearby civilization located within 10 light-years of the Earth, using instrumentation with a sensitivity similar to the Green Bank Telescope. We plan to extend our model to include more powerful 5G mobile systems, radar installations, ground based up-links (including the Deep Space Network), and various types of satellite services, including low-Earth orbit constellations, such as Starlink and OneWeb.

Rapid Response of the Norwegian Atlantic Slope Current to Wind Forcing

Abstract We explore drivers of variability in the Norwegian Atlantic Slope Current, which carries relatively warm Atlantic Water toward the Barents Sea and Arctic Ocean, using Copernicus Marine Environment Monitoring Service (CMEMS) satellite altimetry data and TOPAZ4 ocean reanalysis data. Previous studies have pointed to a variety of causes, on a variety of time scales. We use data with daily resolution to investigate day-to-day changes in ocean transport across three sections crossing the shelf-slope of Norway (Svinøy, Gimsøy, and the Barents Sea Opening). The highest (lowest) extremes in transport at all sections develop over two days as a cyclonic (anticyclonic) atmospheric pressure system approaches from the southwest, piling up (extracting) water at the coast of Norway. The actual peak is reached when the pressure system passes the site of measurement, and the transport then relaxes for the next two days as the system continues northward along the coast. Other sources of short-term variability, such as propagating continental shelf waves and baroclinic instability, are unlikely to yield covariability over large separations. Monthly variability in the current can also be explained by passing weather systems since their numbers and intensity vary greatly from month to month. Many studies of longer-term variability, especially in the Barents Sea Opening, have pointed to the North Atlantic Oscillation (NAO) as the main cause of variability. Our results show that passing weather systems offer a better explanation of month-to-month variability.

Design and Experiment of Satellite-Terrestrial Integrated Gateway with Dynamic Traffic Steering Capabilities for Maritime Communication.

This study presents the architectural design and implementation of a multi-RAT gateway (MRGW) supporting dual satellite and terrestrial connectivity that enables moving maritime vessels, such as autonomous surface ships, to be connected to multiple radio access networks in the maritime communication environment. We developed an MRGW combining LTE and very-small-aperture terminal (VSAT) access networks to realize access traffic steering, switching, and splitting functionalities between them. In addition, we developed communication interfaces between the MRGW and end-devices connecting to their corresponding radio access networks, as well as between the MRGW and the digital bridge system of an autonomous surface ship, enabling the MRGW to collect wireless channel information from each RAT end-device and provide the collected data to the digital bridge system to determine the optimal navigation route for the autonomous surface ship. Experiments on the MRGW with LTE and VSAT end-devices are conducted at sea near Ulsan city and the Kumsan satellite service center in Korea. Through validation experiments on a real maritime communication testbed, we demonstrate the feasibility of future maritime communication technologies capable of providing the minimum performance necessary for autonomous surface ships or digitized aids to navigation (A to N) systems.

Application of remote monitoring and ground-based sensing in pastoralism

The development and implementation of an innovative system applying digital aerospace technologies in pastoralism constitute one of the current trends in agricultural development designed to solve numerous problems associated with soil fertility restoration in grazing pastures. Here, a promising line of research is to explore the feasibility of using satellite systems for an overall nutrient yield assessment per hectare of grazing land. The present article describes a comprehensive approach to the optimization of pastoralism that is based on remote methods for assessing pasture fertility using unmanned aerial vehicles (UAVs) and artificial Earth satellites. An analysis of existing methodological approaches reveals that the formalization of prediction processes is complicated by the lack of a theoretical basis for creating appropriate model-algorithmic support. The data on vegetation index dynamics and the nutritional values of forage plants obtained by interpreting imagery from a UAV camera and the multispectral cameras of a satellite service, as well as data from a portable handheld nitrogen sensor, were compared with the actual nutritional values of pasture plants. The study results provide a means to optimize the grouping of grazing animals, taking into account the actual possibility of achieving an increase in live weight. The provided findings indicate the possibility of achieving an additional 11.06% increase in daily live weight gain in young sheep (Jalgin Merino) when keeping them in pasture areas having a vegetation index of at least 0.5. Remote monitoring based on satellite service allows more efficient use of pastures. Study shows a positive relationship between remote sensing NDVI and feed nutritional value. Animal grazing optimization provides an additional 11.06% increase in live weight gain.

Refinement of NOAA AMSR-2 Soil Moisture Data Product: 1. Intercomparisons of the Commonly Used Machine-Learning Models

Soil Moisture is an important variable for hydrological, meteorological and agricultural studies and applications. The Soil Moisture Operational Products System (SMOPS) was developed by the National Oceanic and Atmospheric Administration (NOAA)-National Environmental Satellite, Data, and Information Service (NESDIS) to operationally provide an integrated satellite soil moisture data product. The Advanced Microwave Scanning Radiometer 2 (AMSR2) soil moisture retrieval is an important component of the currently operational SMOPS. This study is proposed to refine the AMSR2 data product using an optimal machine learning model, and this first paper of the two-part series is to intercompare the six commonly-used machine learning models including multiple linear regression (MLR), Regression Tree (RRT), Random Forest (RFT), Gradient Boosting (GBR), Extreme Gradient Boosting (XGB) and Artificial Neural Network (ANN). Results indicate that all of the six approaches can preserve the reference data information beyond the training time period, which ensures them to predict past and future satellite retrievals without a new training procedure. Relative to other models, the XGB method is more successful to respect to the reference data Soil Moisture Active Passive (SMAP) and the in-situ observations from the U. S. Department of Agriculture Soil Climate Analysis Network (SCAN). It has a good implication on the implementation of the XGB model to refine the AMSR2 soil moisture retrievals in the second paper.

Are Severe Forms of Thyroid Eye Disease Common in the Indian Population? Clinical Characteristics of 136 Patients from a Tertiary Eye Care Centre.

Considerable evidence of gender, ethnicity, thyroid dysfunction, and environmental factors including smoking influencing the development and progression of thyroid eye disease (TED). Cross-sectional study of the clinical characteristics of 136 patients with TED who presented to the Orbit and Oculoplasty services at a tertiary eye care center in south India between October 2018 and June 2020. Among the 136 patients (M: 61, F: 75), the mean age was 47.04 (SD ± 13.24) years. Hyperthyroid disease was present in 53%, hypothyroid disease in 40%, and 7.3% were euthyroid. Active disease was noted in 25% and inactive disease in 75% of patients. Active disease was present in 25% of hyperthyroid, 18.5% of hypothyroid, and 15% of euthyroid patients. Active TED showed statistically significant association toward development of greater severity of proptosis (P = 0.001), optic neuropathy (P = 0.004), and extraocular movement restriction (P < 0.001) as compared to inactive disease. Mild, moderate to severe, and sight-threatening TED was noted in 34.6%, 59.6%, and 6% of patients, respectively. Nine eyes had dysthyroid optic neuropathy, of which eight had either mild or no proptosis while one had moderate to severe proptosis. Prevalence of active as well as severe thyroid eye disease is common in our population. Recommendation for ophthalmological examination of patients even with milder disease especially when associated with decreased vision and signs of inflammation. Active disease is less common in euthyroid patients, thus necessitating maintaining the euthyroid status toward reducing disease activity and progression.

Optimal Orbit Design and Mission Scheduling for Sun-Synchronous Orbit On-orbit Refueling System

This paper proposes a two-stage optimization framework to simultaneously solve the orbit design and mission scheduling problems of on-orbit refueling (OOR) system in Sun-Synchronous Orbit (SSO). The fuel can be delivered to the client satellite (CS) by small-scale service satellites from the on-orbit fuel station (FS), which leads to a new FS-servicer-CS OOR mode. For the first stage, a modified spectral clustering-nonlinear programming (MSC-NLP) method is used to assign CSs to FSs, and design the orbit of FSs under <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> perturbation. For the second stage, the mission scheduling problem is formulated as a mixed-integer nonlinear programming (MINLP) model and solved via the genetic quantum algorithm (GQA). Different from the existing literature, this paper introduces a clustering distance metric combining multiple orbit characteristics for CS assignment, which can indirectly reduce the estimated fuel costs in the FS orbit design. Furthermore, the objective of reducing the number of servicers is first considered in the second stage. The effectiveness and superiority of the proposed two-stage framework are verified through several numerical simulations and comparison studies.

Assessing Potential Performance of GPS and Galileo in context of Broadcast Precise Orbits and Clock Corrections

The global navigation satellite system (GNSS) is becoming a vital positioning technology across various services. The ephemeris quality is one of the factors that directly impact the user's position accuracy. Some applications, such as investigations into Earth's crustal dynamics, need more precise ephemeris data than broadcast ephemeris. Several institutions, such as the international GNSS service (IGS), have developed precise orbital services to enable these applications. Unfortunately, data rates for such precise orbits are often confined to 15 minutes. In this paper, in order to generate precise ephemeris with the broadcast sampling period, the well-known Lagrange interpolation method is used. Furthermore, a comparative GPS and Galileo position analysis corresponding to the broadcast and precise ephemeris over a typical day in September 2021 is presented. To get insight into comparative positioning analysis over Hyderabad Station, the ENU (East-North-Up) directional errors, satellite visibility and horizontal accuracy parameters are considered. Based on the numerical analysis, standalone Galileo has similar capabilities to GPS, and it can be used in Multi-GNSS over India and its surrounding areas. This work may help in the development of single- or dual-frequency GNSS receivers for civilian navigation services.

Low-thrust rendezvous trajectory generation for multi-target active space debris removal using the RQ-Law

The problem of space debris must be addressed to avoid a cascading collision in the near future that would critically damage humanity’s space assets and dependent terrestrial infrastructure. One method of meeting this challenge is to use a dedicated spacecraft to deorbit a series of prioritized debris. To avoid a large fuel requirement, electric spacecraft propulsion can be used, for which a multiple-rendezvous low-thrust trajectory is of interest. In this study, we develop such a trajectory for a predetermined subset of the Iridium 33 debris using a two-step procedure. First, the target rendezvous order is determined by using relevant distance metrics to approximate the transfer cost between debris objects. Next, the RQ-Law, a recently developed Lyapunov feedback control law for generating low-thrust rendezvous trajectories, is used to generate a trajectory that can take a spacecraft to each of the studied debris objects in the determined order. This method can be used to rapidly determine low-thrust multi-target multi-revolution rendezvous trajectories in the preliminary design stage for missions such as space debris removal and satellite servicing without requiring an initial guess.

Interference Analysis of 5G NR Base Stations to Fixed Satellite Service Bent-Pipe Transponders in the 6425–7125 MHz Frequency Band

Future deployment of 5G NR base stations in the 6425-7125 MHz band raises numerous concerns over the long-term impact on the satellite transponders located in geostationary orbit. To study this impact and understand whether 5G NR may cause adverse effect to the spaceborne receivers, the research which estimated the interference levels to the satellite bent pipe links was done. The study presents the evaluation of aggregate interference from 5G NR base stations located inside the victim satellites' footprints using Monte-Carlo analysis and calculation of signal-to-noise degradation and bit error rates of the fixed-satellite service (FSS) bent-pipe transponders for each scenario. The results of the study showed the feasibility of co-existence between 5G NR and satellite systems in the 6425-7125 MHz bands, and that no negative impact on the performance of the satellite links is expected.

BDS-3 RDSS two-way time transfer with asymmetric delay compensation model

In the BeiDou navigation satellite system-3 (BDS-3) radio determination satellite service (RDSS), there exists a natural two-way link between the center station and the user site that can be used to achieve time transfer. Traditionally, RDSS two-way time transfer is realized by analogy with the two-way satellite time and frequency transfer (TWSTFT) technique. However, unlike TWSTFT, the signal propagation delays are not completely symmetrical in the RDSS two-way link because of the differences in signal emission time. In this study, a model of two-way time transfer with BDS-3 RDSS is presented. An asymmetric delay compensation method is introduced to solve the asymmetry of RDSS signals and improve the accuracy of two-way time transfer. In addition, BDS-3 RDSS common clock difference experiments are designed to test the performance of two-way time transfer with an asymmetric delay compensation model. Based on analyses of the experimental results, three conclusions can be drawn. First, the accuracy of RDSS two-way time transfer is improved when the asymmetric delay compensation model is applied. Second, BDS-3 RDSS two-way time transfers in different in-station beams and subbands do not show many discrepancies on the whole, and the standard deviation values of the BDS-3 RDSS time transfer results range from 1.7 ns to 2.6 ns for the test signals. Third, the two-way time transfer results are not generally affected by receiver coordinate errors.

ATG spectrum analysis and interference mitigation for intelligent UAV IoT

As UAV Internet of things applications continue to grow, so does interest in the development of air-to-ground (ATG) systems, which can effectively expand communication system coverage. To maximize utilization of frequency resources, the ATG system adopts frequency reuse with the 5G system on the ground. This research studies the co-channel interference between ATG and 5G at 3.5 GHz as well as the neighboring channel interference with C-band fixed satellite service. We do research on various ATG aircraft flying altitudes and horizontal distances, which yields multiple potential interference reduction strategies. Finally, numerical results are shown to demonstrate the efficacy and productivity of our proposed methods.

Hyper-Redundant Manipulators for Operations in Confined Space: Typical Applications, Key Technologies, and Grand Challenges

In this article, we review the state of the art in hyper-redundant manipulators for applications in confined space such as <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -orbit services. With their multiple degrees of freedom and slender links, hyper-redundant manipulators can offer superior dexterity and excellent operability. They can traverse freely, manipulate objects flexibly, and conform to curvilinear paths accurately in confined spaces. The by-design separation of the mechanical and electrical parts in these manipulators also offers inherent structural compliance and miniaturization. Due to the elastic characteristics of driving cables, hyper-redundant manipulators have both stiffness and flexibility. In this article, the overviews of the current state of the art in this field are provided from the perspectives of both typical applications and key technologies. We detailed the relevant studies on the configuration, obstacle avoidance, path planning, and control technologies for hyper-redundant manipulators and highlight the use of these studies in the development of practical applications. Furthermore, we propose several aspects that need to be further studied, namely efficient inverse kinematics solution, strong coupled dynamics modeling, variable stiffness control, and multiobjective trajectory optimization. Breakthroughs in these areas will provide valuable solutions for complex path planning and control of hyper-redundant manipulators. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup>

Concentration and distribution of phytoplankton nitrogen and carbon in the Northwest Atlantic and Indian Ocean: A simple model with applications in satellite remote sensing

Despite the critical role phytoplankton play in marine biogeochemical cycles, direct methods for determining the content of two key elements in natural phytoplankton samples, nitrogen (N) and carbon (C), remain difficult, and such observations are sparse. Here, we extend an existing approach to derive phytoplankton N and C indirectly from a large dataset of in-situ particulate N and C, and Turner fluorometric chlorophyll-a (Chl-a), gathered in the off-shore waters of the Northwest Atlantic and the Arabian Sea. This method uses quantile regression (QR) to partition particulate C and N into autotrophic and non-autotrophic fractions. Both the phytoplankton C and N estimates were combined to compute the C:N ratio. The algal contributions to total N and C increased with increasing Chl-a, whilst the C:N ratio decreased with increasing Chl-a. However, the C:N ratio remained close to the Redfield ratio over the entire Chl-a range. Five different phytoplankton taxa within the samples were identified using data from high-performance liquid chromatography pigment analysis. All algal groups had a C:N ratio higher than Redfield, but for diatoms, the ratio was closer to the Redfield ratio, whereas for Prochlorococcus, other cyanobacteria and green algae, the ratio was significantly higher. The model was applied to remotely-sensed estimates of Chl-a to map the geographical distribution of phytoplankton C, N, and C:N in the two regions from where the data were acquired. Estimates of phytoplankton C and N were found to be consistent with literature values, indirectly validating the approach. The work illustrates how a simple model can be used to derive information on the phytoplankton elemental composition, and be applied to remote sensing data, to map pools of elements like nitrogen, not currently provided by satellite services.