Satellite Services Research Articles

Procedure for evaluating electromagnetic compatibility of low-orbital satellite data transmission systems subscriber terminals with fixed satellite service earth stations

Procedure for evaluating electromagnetic compatibility of low-orbital satellite data transmission systems subscriber terminals with fixed satellite service earth stations

A reference implementation for knowledge assisted robot development for planetary and orbital robotics

The use of modular, yet reusable and interchangeable components offers flexibility for system designers and thus leads to a higher degree of reconfigurability with cost effective, adaptable and scalable solutions. The development of a robotic system remains, however, a complex task with increasing demands depending on the targeted capabilities, functionalities and operational constraints of the robot. This requires expert knowledge in mechanical, electrical and software engineering, as well as tools that can collect, process and use relevant data. As a result, the amount of available and managed information is increasing, while its relevance, usability, and knowledge that can be extracted from it are consequently decreasing: a situation described as information overload paradox.The design of a modular system can be based on the use of standardized modules with universal interconnects, but it should be aligned with a strong formalism, e.g. the semantic representation of components, to allow for a better management of the overall complexity. An ontology-based knowledge representation, for instance, which provides domain and application specific knowledge for the design of robotic systems, can be used as a method of storing and sharing data in a uniform, machine-readable and standardized way.In this paper, we introduce the Knowledge-based Open Robot voCabulary as Utility Toolkit (korcut) as a core component to support the ontology-driven development of robotic systems as part of a reference implementation of the Q-Rock development cycle. Q-Rock gathers methods to assist users in designing robot configuration by: (a) automatically exploring robot capabilities based on robot hardware, (b) proposing robot designs to meet the user’s needs, (c) refining the proposed robot designs. We use korcut to improve the robot design process in orbital and planetary robotics from the requirements definition to the development phases of complex modular robotic structures (e.g. composition of an unmanned ground vehicle with robotic arms). This is implemented by embedding semantic component descriptions in a state-of-the-art open-source 3D modeling software. Furthermore, the korcut ontology family includes various sub-ontologies to address specific space-related tasks, such as the modeling of a Standard Interconnect (SI) for On Orbit Services (OOS) and Orbital Factory. The ontology design follows criteria that have been derived from a survey conducted as part of this work. This paper also covers an evaluation of its current applications from a methodological, knowledge representation, and software tool perspectives. In the application part, we introduce the use of the ontology to model a multi-functional SI that enables mechanical connections between various (modular) robotic components, as well as transfer of power and data. Finally, we provide a critical analysis of our work and outline its future work.

Assembly Error Modeling and Tolerance Dynamic Allocation of Large-Scale Space Deployable Mechanism toward Service Performance

As a satellite’s critical load-bearing structure, the large-scale space deployable mechanism (LSDM) is currently assembled using ground precision constraints, which ignores the difference between the ground and space environments. This has resulted in considerable service performance uncertainties in space. To improve satellite service performance, an assembly error model considering the space environment and a tolerance dynamic allocation method based on as-built data are proposed in this paper. Firstly, the factors influencing the service performance during ground assembly were analyzed. Secondly, an assembly error model was constructed, which considers the influence factors of the ground and space environment. Thirdly, on the basis of the assembly error model, the tolerance dynamic allocation method based on as-built data was proposed, which can effectively reduce the assembly difficulty and cost on the premise of ensuring service performance. Finally, the proposed method was validated in an assembly site, and the results show that the pointing accuracy, which is the core indicator of the satellite service performance, was improved from 0.068° to 0.045° and that the assembly cost was reduced by about 13.5%.

Toward Coherence: A Space Sector Public-Private Partnership Typology

Since the rise of public-private partnerships (PPPs) in the late 20th century, academia has engaged in critical discussions around the phenomenon and industrial organizations have developed numerous guidelines and best practices. An analytical tool that has enriched the depth of the discussions is typology. Typologies help to deconstruct complex phenomena, develop analytical frameworks, and conduct empirical investigations. With the New Space evolution and the success of National Aeronautics and Space Administration's Commercial Orbital Transportation Services, PPPs have become a frequent procurement arrangement in the space sector. Because of their theoretical benefits, PPPs are politically popular and are supported by major government space policies. However, the space policy literature uncritically praises and promotes such procurement arrangements without examining their merits. As the sector begins employing more PPPs, it is necessary to engage in critical discussions built on empirical evidence. This study presents a typology specific for space PPPs to provide a standardized language for investigations and bring coherence to the term “PPP” in the sector. The typology development involved mini-case studies of 20 space programs, and the framework embodies a well-established typology approach.

On precise orbit determination based on DORIS, GPS and SLR using Sentinel-3A/B and -6A and subsequent reference frame determination based on DORIS-only

The Helmholtz-Zentrum Potsdam GFZ German Research Centre for Geosciences is one of the Associate Analysis Centers of the International Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) Service (IDS). In the framework of a recent reprocessing campaign for the International Terrestrial Reference Frame (ITRF) the suite of DORIS-derived satellite products was extended and improved with respect to reference frame determination. Among others the Copernicus Sentinel-3A/3B and 6A Michael Freilich (MF) satellites were used for this purpose. The orbits were generated based on DORIS-only and on the combination of DORIS and Satellite Laser Ranging (SLR) observations, and attempts were made to optimize their accuracy. Also for these satellites, GFZ generates Global Positioning System (GPS) based orbits within the Copernicus Precise Orbit Determination (CPOD) quality working group (CPOD-QWG). The GPS orbits contribute to a combined CPOD orbit solution, which is assumed to have superior absolute accuracy and minimal residual systematic errors. The DORIS-only, the combined DORIS and SLR, and the GPS-only orbits are compared to the CPOD combined solution serving as reference solution. The accuracy of the orbits shows up in radial direction for all techniques and combinations with values of 0.60 to 0.82 cm. In transverse and normal direction the RMS values achieved with GPS are up to around 50% lower as with DORIS, which sizes at around 1.5–2 cm. Subsequently the reference points of the observation techniques were estimated. With a multi-technique approach, a center-of-mass deviation according to Montenbruck et al. (2017) could be reproduced for Sentinel-3A. In addition, for both Sentinel-3 satellites the DORIS reference point values show a deviation in normal direction of 8–9 mm and a drift in radial direction of about 3 mm/year with respect to manufacturer’s data, reference point values for Sentinel-6A (MF) show a good agreement. With the confidence gained on the DORIS-only orbit solutions, weekly local reference frames are computed for each of the three satellites as well as a combined solution and evaluated in terms of the reference frame defining parameters, i.e. origin, scale, and orientation. The accuracy achieved here is in the range of a few mm to cm region. The scale remains stable, except for Sentinel-3A, which shows a scale drift of about −1.5 mm/year, whose cause is not clear yet. Standard deviations of station coordinate residuals (North, East, Up) are in the range of 2–4 mm, 5–9 mm and 5–7 mm respectively.

Algorithmization of Guidance and Motion Control of a Space Manipulation Robot in the Service Tasks of a Non-Operative Spacecraft

Nowadays there are many non-functioning spacecraft in orbit that have run out of fuel, or have failed due to breakdown. Therefore, the concept of a serviced space and the development of space manipulation robot for extending the spacecraft service life are becoming expedient. Space manipulation robot will be able to perform a variety of tasks, from inspecting malfunctions of a serviced spacecraft, to performing repairs and refueling the target vehicle. The article proposes a strategy and algorithms for the guidance and motion control of a space manipulation robot at the stage of rendezvous with a non-cooperative spacecraft to perform maintenance tasks. The purpose of the article is to synthesize the control of the translational and rotational motion of the space manipulation robot for its convergence with the target satellite at a given distance. The control system is presented in the form of a hierarchical two-level "guidance-stabilization" system. At the guidance level, a transition quaternion of the associated coordinate system to the required position is formed, as well as thrust engine control, which ensures the translational motion of the space manipulation robot at the required velocity. At the stabilization level, a control is formed that superpose the associated coordinate system of the space manipulation robot with the direction to the served satellite. The article proposes a scheme and a mathematical model of the propulsion system, angular and translational motion of the service satellite. The modeling of the developed guidance and motion control algorithms in the SIMULINK environment has been carried out.

JEDI‐Based Three‐Dimensional Ensemble‐Variational Data Assimilation System for Global Aerosol Forecasting at NCEP

AbstractA three‐dimensional ensemble‐variational global aerosol data assimilation system based on the Joint Effort for Data assimilation Integration (JEDI) was developed for the Global Ensemble Forecast System‐Aerosols (GEFS‐Aerosols) coupled with the Goddard Chemistry Aerosol Radiation and Transport (GOCART) model at the National Centers for Environmental Prediction. Aerosol mass mixing ratios in GEFS‐Aerosols were selected as control or analysis variables and were adjusted by assimilating 550 nm Aerosol Optical Depth (AOD) retrievals from the Visible Infrared Imaging Radiometer Suite (VIIRS) instruments onboard the Suomi National Polar‐orbiting Partnership (S‐NPP) satellite produced by the National Environmental Satellite, Data, and Information Service (NESDIS) at National Oceanic and Atmospheric Administration (NOAA). The original NOAA/NESDIS S‐NPP VIIRS Level 2.0 550 nm AOD retrievals were converted to JEDI Interface for Observation Data Access format. AOD forward operator and its tangent‐linear and adjoint models were implemented based on GOCART in JEDI Unified Forward Operator. A stochastically perturbed emission (SPE) approach was developed in the Common Community Physics Package‐based GEFS‐Aerosols to account for aerosol emission uncertainty. One‐month retrospective and three‐month near‐real‐time experiments consistently showed improved GEFS‐Aerosols analyses and forecasts from assimilating VIIRS 550 nm AOD retrievals against independent NASA Aqua and Terra Moderate Resolution Imaging Spectroradiometer AOD retrievals, Aerosol Robotic Network AOD, and independent AOD and aerosol analyses from NASA and European Centre for Medium‐Range Weather Forecasts. Through scaling and perturbing aerosol emissions, SPE enhanced ensemble error‐spread consistency and further improved AOD assimilation. The valid‐time‐shifting ensemble approach in a cost‐effective manner of populating background ensembles showed positive impacts on AOD assimilation.

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

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

Guard band protection for coexistence of 5G base stations and satellite earth stations

In this paper, the coexistence between fifth generation (5G) network and fixed satellite service (FSS) is investigated. To reduce the interference between 5G base stations (BSs) and FSS earth station (ES), a guard band protection method is proposed. Additionally, the distance and angular protection methods are amalgamated. The performances are evaluated by simulation in realistic 3GPP. Also, the impacts of four antenna types are analysed for a 5G BS. The numerical results show that the guard band protection can solve the interference for the 5G/FSS coexistence, when the distance protection is combined. In addition, when the hybrid protection method is employed, the coexistence between 5G BS and FSS ES is guaranteed.

Design and analysis of single layer Ku/K band integrated element reflectarray antenna

AbstractA linearly polarized dual band reflectarray (RA) antenna designed, fabricated, and tested to operate in the Ku and K band frequencies is reported in this paper. The 24 × 24 cm2 size RA is developed using 1058 integrated elements etched over a 0.275 mm thick Rogers RT5870 substrate. The integrated elements include concentric circular rings distributed co-centric with the source and the Malta cross elements distributed offset from the source. The distribution of these elements is done based on the 590 and 360° phase change observed at 14.25 (Ku) and 22.5 (K) GHz by varying the size of the circular rings and the Malta cross respectively. The designed RA offers a simulated gain of 28.62 dBi at 14.25 GHz and 26.92 dBi at 22.5 GHz. These results are validated experimentally using the fabricated prototype. A measured peak gain of 28 and 26.4 dBi are observed with sidelobe levels (SLL) of −21 and −11 dB at 14.25 and 22.5 GHz respectively. The cross-polarization levels measured at the resonant frequencies are <−31 and <−28 dB. The proposed dual-band RA covers the entire Ku band uplink frequencies utilized for fixed satellite services and the K band downlink frequencies useful for earth exploration satellite services.

Electronically Controlled Frequency Agile Beam Scanning Reflectarray Antenna with Integrated Control Unit

This paper reports the design, development, fabrication, and testing of a 225-element reconfigurable reflectarray (RRA) antenna with frequency agility and beam steering capabilities. The 15 15 (18.75 cm) RRA operating in the Ku band downlink frequency range (11.8 -12.2 GHz) of fixed satellite services (FSS) produces dual resonances switched between uplink frequency range (15-18 GHz) of FSS and earth exploration satellite range of 9.5-9.8 GHz (X Band). To attain reconfigurable multiple resonances, the unit cell is designed with a Malta cross of varying slot lengths interconnected to a square ring via a PIN diode. In the OFF state of the PIN diode connected between the concentric elements, a phase variation of 360° is obtained at 12 GHz and 9.5 GHz by varying the size of the Malta cross. By increasing the width of the outer ring in the ON state of the PIN diode, a dual resonance is obtained at 12 GHz and 17 GHz with 360° phase agility. The beam scanning is attempted at X band frequency by controlling the capacitance offered by the varactor diode connected between an inductive element and Malta cross. The proposed RRA offers 22.16 dBi, 24.5 dBi and 18.43 dBi simulated gain at 17 GHz, 12 GHz, and 9.5 GHz respectively. The simulated sidelobe levels (SLLs) and cross-polarization levels are -14.7 dB and less than -32 dB respectively. The proposed compound reconfigurable reflectarray befits fixed and mobile satellites, earth exploration satellites, radiolocation, aeronautical radio navigation, and deep space research.

A multi-sensor optical relative navigation system for small satellite servicing

This paper presents an innovative multi-sensor relative navigation module conceived to enable close-proximity operations for on-orbit servicing of small satellites. The module is composed of a Near-Infrared Laser Range Finder, acting both as range measurer and illuminator, and a monocular camera able to detect a set of reflecting fiducial markers installed on the target for pose estimation. Sensor fusion is performed in several points of the proposed processing pipeline, first following a cross-cueing logic in which the range aids the pose determination process, and later through the integration of both measurements into a Multiplicative Extended Kalman Filter for relative state estimation. The entire relative navigation architecture is first tested by numerically reproducing a close-range rendezvous trajectory of a chaser spacecraft moving toward the target, and using the open-source software Blender for synthetic image generation. Simulations are aimed at determining nominal relative state estimation accuracy (also considering variable sensors' acquisition rates) as well as performance under non-nominal conditions (e.g., due to a temporary loss of measurements). Focusing on the image processing and pose estimation pipeline, an in-depth analysis of the computational efficiency is then carried out by running the proposed algorithms on an embedded processing unit (i.e., the Raspberry Pi 4 Model B) using both synthetic data and real images collected within a dedicated experimental testbed. Numerical and experimental results demonstrate capability to attain pose and relative state estimates in line with accuracy requirements to ensure autonomous and safe close-proximity operations, e.g., up to sub-cm and sub-degree error levels in relative position and attitude respectively. In addition, the algorithm's computational runtime has shown to be compatible with real-time implementation at an acquisition frequency of 2 Hz.

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.