Earth Station Research Articles

Control system design for azimuth position of earth station antennas

Smart earth station antennas have been used for several decades in many applications, from satellite communications to space object detection and tracking. The accuracy of the azimuth position for such antennas plays a crucial role in most steerable ground station antennas. Satellite tracking and space object detection demand precise tracking capabilities from the Earth. Several methods and techniques have been developed and used in industry to control the directions of ground station antennas, including the azimuth position. The challenge of azimuth tracking is increasing with the demand for full-sky coverage and with the exponential increase in space objects, including man-made satellites and operational and nonoperational objects; thus, providing accurate tracking is a key technology that demands continuous enhancement and development. This article presents the use of a PID-proportional-integral-derivative controller, a slide mode controller and a fractional order PID controller. It also introduces a new methodology based on model predictive control (MPC). The manuscript provides the core design for each of these controllers and provides insight into the performance of each controller even in the presence of disturbance. The camel optimization algorithm (COA) was used to obtain the optimal design parameters of each controller in the considered scenarios.

Theoretical Substantiation of Methods for Reducing the Near-Side Radiation of Antennas for an Earth Satellite Communication Station

Within the framework of this article, various methods of reducing the lateral radiation of the antenna are considered, which mainly relate to the angular directions directly adjacent to the direction of the main radiation of the antenna for an earth satellite communication station. The relevance of this issue is beyond doubt, since it is the behavior of the antenna's diagrammatic orientation in this area that most significantly determines the electromagnetic compatibility of various satellite communication systems. The presence of axial shading leads to a significant increase in the near side lobes. The specified deformation of directional properties in a certain plane can be eliminated by using an additional radiator, the phase center of which in this plane coincides with the phase center of the antenna. Shadow radiation compensation is carried out only in a beam of regions close to the plane perpendicular to the straight line connecting the centers of the main and auxiliary antennas. The angular compensation area can be significantly expanded if the phase centers of the main and auxiliary antennas are combined. This rather trivial conclusion is still waiting for its non-trivial technical implementation. Wide-angle compensation of lateral radiation is proposed to be carried out by two auxiliary antennas located parallel to the suppression plane. The best results can be obtained by optimizing the opening shape of the auxiliary radiators. Studies show that the optimal variant of the directional pattern occurs when the mentioned irradiators are made in the form of rectangles with a length of 0,295 and a height of 0,117 from the opening radius of the main antenna, and the distribution in the openings of the auxiliary antennas is cosine-shaped. In this case, it is possible to suppress the radiation level to -40 dB.

Collaborative last-hop scheduling strategy for large-scale LEO constellation routing

The transmission of data packets from satellites to Earth Stations (ESs) is the last hop of satellite network routing. As the final stage of packet transmission, the use of different scheduling strategies directly affects the throughput of the satellite network. Traditionally, researchers have attempted to enhance network performance by investigating inter-satellite routing protocols or inter-satellite data offloading strategies. However, these approaches have failed to address scheduling issues in the last hop of large-scale Low Earth Orbit (LEO) constellations. In this paper, we present the first Cooperative Last-Hop Scheduling (CLHS) strategy for routing in large-scale LEO constellations based on a bidirectional communication domain. In this strategy, we first utilize the bidirectional communication domain to determine the communication ranges of satellites and ESs. Subsequently, an information flow is established to interact with ESs and satellites. The ESs receive and reconstruct the Information Matrix (IM) from the information flow. Moreover, we propose the Maximum Decision Value Priority (MDVP) algorithm, which takes the reconstructed IM as input and computes the scheduling commands for satellites within the communication range of the ESs. To address the issue of multiple ESs simultaneously scheduling the same satellite, we introduce the Collision Avoidance Algorithm (CAA). Finally, to enhance the data packet transmission efficiency of the scheduled satellites, we propose the Weighted First-In-First-Out (WFIFO) algorithm, which is specifically designed for satellite packet dequeuing. We validate the CLHS through simulations on two satellite constellations: the first-generation Starlink constellation with 4409 satellites and the GW-2 constellation with 6912 satellites. The results show that CLHS can achieve better network throughput than traditional strategies. CLHS provides a novel method of scheduling the last hop in large-scale satellite constellations.

Planetary media: Decolonizing the space industry through Indigenous ownership

The colonial relationship between Indigenous people and people of European origin has been characterized by conflicts, economic exclusions, and epistemological discriminations as well as the mutual sharing of knowledge, practices, and technologies. In many cases, the industrial development of space technologies such as telescopes and rocket test sites has continued the exploitative nature of colonialism. This article, however, offers a different story and concept of Indigenous decolonization that is not antagonistic but complementary to the space industry and Western liberalism more generally. The case is Space Enterprises, a company and Earth station owned by the Center for Appropriate Technologies in Alice Springs, Northern Territories, Australia and conceived by its Aboriginal owners, workers, and board of directors as representing a beneficial integration of their Indigenous self-determination and the space industry. This essay offers synthetic decolonization as an example of this integration with Western liberalism. Understanding the flows between the Indigenous-owned Earth station and satellites, as well as the connections between Indigenous and Western liberal planetary imaginaries, requires a theory of mediation. Towards that goal, planetary media is offered as a way of conceptualizing the flows of information between local Indigenous and planetary spaces and imaginaries. This essay argues that another decolonization is possible, one based on mediation between Indigenous and Western liberal systems of thought.

Operational Cost Models for an Earth Station System Using 2-Parallel and 4-Parallel Configurations

Operational Cost Models for an Earth Station System Using 2-Parallel and 4-Parallel Configurations

A study on THz communications between Low Earth Orbit constellations and Earth Stations

A non-terrestrial system that uses Terahertz (THz) frequencies is a potential solution to achieving equal access to the Internet worldwide. This paper describes a non-terrestrial system that consists of a Low Earth Orbit (LEO) constellation, Earth Stations in Motion (ESIMs) and standard Earth stations. We examine the effects of rain, fog, clouds and atmospheric gases for this non-terrestrial system for frequencies between 100-300 GHz. The research findings suggest that the frequency bands between 102 - 109.5 GHz are rather suitable for communication between Earth stations and satellites, including ESIMs, reaching in a critical scenario uplink data rates of up to 2.6 Gbits/s with 0.5 GHz of bandwidth or up to 12 Gbits/s with 5 GHz of bandwidth in uplink. For the downlink, we can reach up to 6 Mbits/s with a transmitted power of 29 dBW, but if we increase the power transmitted by satellites, it is possible to reach up to 25 Gbits/s with 2.5GHz of bandwidth. Under clear, blue-sky conditions, we can achieve a maximum data rate of 17.3 Gbits/s for downlink and uplink. For inter-satellite links (communications between satellites in the same orbit or between different orbits), the frequency bands between 111.8 - 114.25 GHz, 116 - 123 GHz, 174.5 - 182 GHz, 185 - 190 GHz are viable, offering speeds from 1.5 to 2.51 Gbits/s when using a uniform rectangular array with 625 radiating elements. This research provides new findings from the amalgamation of existing literature, which is crucial for the future allocation of optimal frequencies between 100 - 300 GHz for satellite services.

Seasonal Variation of Total Attenuation between Airborne Platform and Earth Station in South-West Region, Nigeria

The seasonal variation of total attenuation in the southwest region of Nigeria has been computed using eight (8) years dataset at Ku- and Ka-band of the transmitted power of the radar, transmitted antenna gain and the received antenna gain of the satellite retrieved from the archived of the GPM. The results obtained fluctuates between the seasons at Ku- and Ka-band. From the results obtained at Ku-and Ka-band, the results from analysis showed that the peak total attenuation was recorded between the early (MAM) and late wet (JJA) season when the intensity of rainfall is maximum in the South-West region. As a result, the effect on the airborne-earth station link will be severe which may further lead to signal outage. However, the state where the highest total attenuation was consistent is Lagos state. These seasons and Lagos state must be taking into consideration by engineers and radiowave propagation group when planning and sitting radiowave propagation in the study area.

The engineering face-lift of the 32m dish: technical upgrades of Ghana Radio Astronomy Observatory (GRAO)

Ghana's 32-meter radio telescope, inaugurated in August 2017, was once a redundant telecommunications dish that underwent conversion. Prior to this transformation, feasibility studies were conducted to assess the dish's structural integrity, technical compatibility, and economic viability. These studies aimed to determine if the conversion project could be technically achieved given the available technology, expertise, and resources. This paper delves into the engineering considerations surrounding structural, mechanical, software, control and monitoring, radio frequency, and timing frequency reference requirements that distinguish the operation of a radio telescope from its former role as a satellite earth station. Significant components such as the azimuth bearing, sub-reflector support, cable wrap, and electrical motors underwent replacement. Additionally, a new C-band receiver, radio frequency controller, active hydrogen maser timing frequency, and software were developed. Testing protocols to meet science requirements for both single-dish observations and Very Long Baseline Interferometry (VLBI) are also discussed. The conversion process proved to be lengthy and encountered numerous unforeseen circumstances, yet it provided invaluable learning experiences for a developing country like Ghana.

A Robust Sidelobe Cancellation Algorithm Based on Beamforming Vector Norm Constraint

Sidelobe cancellation (SLC) is a well-established beamforming technique for mitigating interference, particularly in the context of satellite communication (SATCOM). However, traditional SLC suffers from the issue of partially canceling the desired signal at high signal-to-noise ratio (SNR), primarily due to unconstrained beamforming processing. Extensive research has been conducted to address this problem; however, existing algorithms have limitations such as dependence on knowledge of signal array vectors or number of interferers and involve high computational complexity. In this paper, we propose a robust SLC algorithm based on beamforming vector norm constraint. Our proposal offers a practical solution by only requiring knowledge of the earth station antenna gain and maximum auxiliary array gain to the desired signal, both of which are fully known. Furthermore, compared to traditional SLC, our proposed method introduces additional computational complexity that only scales linearly with the size of the auxiliary array. Simulation results demonstrate comparable performance between our proposed method and existing techniques such as diagonal loading and spatial degrees-of-freedom control-based algorithms.

RESEARCH OF THE FEATURES OF DIGITAL SIGNAL FORMATION IN SATELLITE COMMUNICATION LINES

Context. Remote sensing of the Earth is now widely used in various fields. One of the challenges of remote sensing is the creation of inexpensive satellite systems operating in polar circular orbits. These systems require the development of a receptiontransmission system that allows tens of gigabits of video information to be transmitted to an earth receiving station within ten minutes. That is, there is a need to create a communication system that provides high speed data transmission from small satellites weighing up to 50 kg.
 Objective. The aim of the work is to study the features of digital signal formation in modern satellite communication lines and to develop a communication system with a high data transfer rate (usually 300 Mbit/s), which can be applied to small Earth Observation satellites.
 Method. Proposed concept for building a high-speed data transmitter from a remote sensing earth satellite using commercially available off-the-shelf technology. Calculations of the power flow density created at the input of the receiving earth station were performed to find out the possible power of the on-board transmitter.
 Results. A diagram of a communication system based on the DVB-S standard using the technology of commercially available off-the-shelf products has been developed. The high-speed data transmitter is implemented on a Xilinx® Zynq Ultrascale+ ™ MPSoC FPGA microchip, which is located on an Enclustra Mercury XU8 module with a high-performance dual 16-bit AD9174 DAC. The on-board transmitter with a power of up to 2 W meets the requirements of the ITU Radio Regulations for the power flux density on the surface of the Earth, which is created by the radiation of the space station EESS in the range 8025–8400 MHz. It is shown that the energy reserve of the communication line of 3 dB is achieved for various commands for coding and modulation changes with an increase in the elevation angle, which allows to increase the speed of information transmission.
 Conclusions. An original receiving-transmitting system was developed for use in small satellites for remote sensing of the Earth. It is shown that the function of adaptive modeling of ACM of the DVB-S standard allows you to automatically change the transmission parameters in real time depending on the changing conditions of the channel, providing opportunities for more flexible and effective data transmission in various conditions, which will allow to increase the volumes of information transmitted by communication session. The proposed system operates in the X-band and is built using commercially available off-the-shelf products. An antenna with double circular polarization is used as the emitter. Two physical channels represent two polarization modes: right circular polarization and left circular polarization, each of which has three frequency channels.

A novel optimization method for attenuating multi‐interferences in satellite communication earth station

SummaryThe study of multi‐interferences plays a pivotal role in advancing the development of next‐generation, high‐performance communication devices. In this paper, we propose a design approach for auxiliary antennas aimed at mitigating multi‐interference challenges within satellite communication earth stations. We introduce an eight‐element auxiliary antenna with an elliptical beam comprising dual radiation patches and a T‐shaped power divider, to attenuate interferences originating from three distinct directions. To enhance the azimuthal beamwidth, we adjust the dimensions of the ground plane and extend the substrate. At a frequency of 12.5 GHz, the antenna exhibits a 3‐dB beam spacing of 38° and an azimuthal width of 162°, with a maximum gain of 7.9 dBi. We employ a sidelobe canceller to optimize the antenna's performance, and both simulations and measurements affirm that the auxiliary antenna achieves an extinction interference cancelation ratio exceeding 27 dB under all circumstances.

Development of novel high anti-pollution polyamide/polysulfate disk tubular reverse osmosis membrane modules and their application in simulated space bathing wastewater

Water is a precious resource in space stations, and wastewater recycling is necessary to meet the needs of astronauts. In that respect, applying the high anti-pollution disk tubular reverse osmosis (DTRO) technique is a reliable way to remove pollutes from wastewater. Thin film composite (TFC) membrane treatment is the most frequently employed solution for purifying wastewater in industry; however, the intrinsic weaknesses of polymer membrane substrates, e.g., poor mechanical property, foulant adsorption and low resistance to acidic/basic conditions, greatly hamper their applications. In this study, the novel polysulfate (PSE) membrane substrates were prepared via non-solvent induced phase separation (NIPS) method. The microstructure and performance of PSE membrane substrates were comprehensively investigated at varying polymer concentration and nanoparticle types. The results showed that adding nanosilver to the support layer significantly enhanced the TFC- PSE/Ag membrane performance (up to 57 %) and tensile strength (by 4.57 ± 0.13). According to computational fluid dynamics (CFD) simulations, the optimized geometric design of deflectors would have noticeably improved the flow field distribution and strength, which was consistent with experimental data. The DTRO modules enabled the effective management of wastewater using simulated space bathing wastewater. The effluent met the water reuse criteria in terms of COD concentration, NH3-N concentration, conductivity and turbidity whose respective values were 15 mg/L, 0.21 mg/L, 60 μS/cm, and 0.9 NTU. The proposed DTRO modules own antifouling and acid/alkaline-resistance, indicating their remarkable application potential in the large-scale recovery of bathing wastewater from the earth or space station.

Near Real-Time Remote Sensing Based on Satellite Internet: Architectures, Key Techniques, and Experimental Progress

Remote sensing has become an essential tool for geological exploration, disaster monitoring, emergency rescue, and environmental supervision, while the limited number of remote sensing satellites and ground stations restricts the timeliness of remote sensing services. Satellite Internet has features of large bandwidth, low latency, and wide coverage, which can provide ubiquitous high-speed access for time-sensitive remote sensing users. This study proposes a near real-time remote sensing (NRRS) architecture, which allows satellites to transmit remote sensing data via inter-satellite links and offload to the Earth Stations from the satellite that moves overhead. The NRRS architecture has the advantages of instant response, ubiquitous access, and intelligent integration. Based on a test communication constellation, a vehicle-mounted Satcom on-the-move experiment was conducted to validate the presented NRRS architecture. The results show that the whole process from demand collection to image acquisition takes no more than 25 min, which provides an engineering reference for the subsequent implementation of near real-time remote sensing.

Satellite-Terrestrial Integrated 6G: An Ultra-Dense LEO Networking Management Architecture

With the rapid development of low earth orbit (LEO) satellites, the ultra-dense LEO satellite-terrestrial integrated networking has become a promising paradigm to provide wide coverage, high capacity and flexible services for the sixth generation (6G) mobile communication networks. However, the natural heterogeneity, high dynamics, and large scale of ultradense LEO satellite networks pose new challenges to network control and management. To this end, in this article, we propose a medium earth orbit (MEO), low earth orbit (LEO) and satellite Earth stations (SESs) integrated multi-layered management architecture for the ultra-dense LEO satellite network, where global controllers and local controllers are introduced to reduce the network management complexity. With the aid of this hybrid multi-layered management framework, we can efficiently implement the network status control, mobility management, resource management, and service management in the satelliteterrestrial integrated network. To obtain proper global and local controllers with high management efficiency in the hybrid multilayered network management architecture, we further propose a novel and efficient grouping and clustering method for the ultradense LEO satellite network, where each group manager MEO satellite and cluster head (CH) LEO satellites are respectively considered as the global and local controllers of each LEO satellite group. Numerical simulations are carried out to evaluate the superiority and effectiveness of the proposed hybrid multilayered ultra-dense LEO networking management architecture.

Resonant Radar Reflector On VHF / UHF Band Based on BPSK Modulation at LEO Orbit by MRC-100 Satellite

This paper presents a novel method for identify ing and tracking PocketQube satellites: the MRC-100 satellite is a model, and this method is based on a resonant radar reflec tor. The resonant reflector’s basic concept is that the resonant reflector uses a VHF/UHF communication subsystem antenna; there is no radiated RF signal, which means the power con sumption is only some Milliampere (mA). The continuous wave (CW) illuminator RF source is on the ground, and the onboard antenna receives the CW RF signal from the Earth. The micro controller (uC) periodically switches PIN diode forming BPSK modulated signal reflection so that another Earth station can receive the backscattered Binary Phase Shift Keying (BPSK) modulated signal. Also, it can detect the satellite if the ground station receiver can use a matched filter like a correlation re ceiver. If the ground station receiver knows the BPSK code of the satellite, it can detect it. If not, there is no way to detect the satellite. This method is similar to Radio Frequency Identifica tion (RFID) applications, but the reader is the ground station, and the tag is the satellite.

Emulation and Testbed Prototyping of Laser Beam Propagation Characteristics through Atmospheric Turbulence for Optical Satellite Feeder Links

Two classical scenarios in space communications can be examined to evaluate the link performance of free space optical communications (FSO). These scenarios include the downlink and uplink between earth ground stations and near earth geostationary (GEO) satellites, as well as between the earth and spacecraft that are located a significant distance from the earth (i.e., one or more astronomical units (AU) away). Deep space is often defined as being more than 0.01 AU, or around 1,500,000 km, from Earth. In the first part of this analytical research, various practical system characteristics for optical lasers, telescopes, transmitters, receivers, and atmospheric disturbances, including absorption and scintillation, are taken into consideration. The simulation outcomes were compared to significant experimental data from DLR & JAXA’s OICETS/Kirari-Japan to validate the extended simulation model. Additionally, this work will propose a synthetic effects-based optical turbulence generator in order to deeply investigate atmospheric turbulence disturbances in free-space optical communication systems and support the advancement of artificial intelligence processing-based mitigation solutions. Worth mentioning, the initial outcomes and analytical comparisons demonstrate the preliminary viability of the simulation model for the link budget and scintillation estimation for FSO investigations, which can give deep insight into the development of the proposed testbed prototyping, machine learning-based laboratory measurement system, and enhancement possibility for FSO project design and execution for longand medium-term space mission planning.

Computational Tool for Rain Attenuation and Gaseous Absorption in Geostationary Satellite Links

This paper presents a computational tool for the calculation of gaseous absorption and rain attenuation in satellite communication systems with a geostationary orbit (GEO). Th software designed, planned, and implemented is based on MVC architecture that separates the code of the stages obtaining a clear and efficient structure. The software has a flow divided into three parts to process the algorithm (model, views, and controller). The software uses some forms to interact with the user and present the results of the computations in a friendly way. Additionally, to this, the program gives some files pdf to show the results and can be updated in its earth stations and satellites database.

SYSTEM REQUIREMENTS FOR TELEVISION BROADCASTING EQUIPMENT IN RUSSIA

The operation of uncertified broadcasting equipment located in 85 regions of Russia is the most important problem in the development of regional broadcasting networks in the absence of system requirements for network transmitters and earth stations of satellite repeaters in the «Digital Broadcasting Television. System of terrestrial terrestrial digital television broadcasting of the second generation DVB-T2. Second generation terrestrial digital television broadcasting system DVB-T2» domestic standard. Standard system requirements are the basis for actualization of requirements to the equipment during its certification. Requirements for network transmitters and earth stations of satellite repeaters in single-frequency broadcasting networks based on the author's research, published in domestic and foreign articles, protected by patents of the Russian Federation, are presented. In particular, the system requirements to the equipment for regional multiplex formation, metrological support of SFN (Single Frequency Network) operation and distributed system of DVB-T2 standard broadcasting quality monitoring are formulated. Requirements for assessing the efficiency of SFN networks, which will make it possible to further modernize existing regional networks to improve their reliability and the quality of television and radio broadcasting in all 85 regions of the Russian Federation, and to certify equipment in accordance with the resolution of the Government of the Russian Federation are also presented. The results of the author's research will make it possible to develop a system project for the creation of digital terrestrial television broadcasting in four new regions of Russia. The prospects for the development of DVB-T2 standard equipment at the program level are considered.

Load-Balanced Collaborative Offloading for LEO Satellite Networks

Low earth orbit (LEO) satellite networks have become one of the hot research areas as an essential part of satellite communication networks. The dynamic topology and unbalanced traffic demand may lead to inter-satellite link congestion, thus, improving network load balancing performance is one of the key issues to be addressed in LEO satellite networks. We propose a load-balanced collaborative offloading (LBCO) strategy to achieve a balanced traffic distribution in LEO satellite networks. LBCO strategy consists of two algorithms, namely, channel-aware gradient fair association (CAGFA) algorithm and inter-satellite links collaborative offloading (ISLCO) algorithm. The CAGFA algorithm aims to maximize the aggregate weighted utility, and the ISLCO algorithm aims to achieve the traffic offloading and download observation data from the LEO satellite network. Specifically, we first determine the actual downloading satellite set and neighboring satellite set by constructing an earth station (ES) time-share graph and a space-time topology graph. Then, the LBCO strategy uses the CAGFA algorithm to obtain the optimal satellite terminal association indicator and the load of downloading satellites. Finally, the ISLCO algorithm is proposed to achieve proportional offloading of traffic among the neighboring satellites and download massive observation data. Simulations show that the proposed CAGFA algorithm improves the weighted utility by 3.3% and the convergence by 47.6% compared with the benchmark stochastic gradient descent-based association (SGDA) algorithm. We also validate the performance of the LBCO strategy by data download throughput, which performs better than other benchmark algorithms under three different load scenarios.

MODEL FOR CALCULATION OF THE ENERGY POTENTIAL OF A SATELLITE RADIO LINK WITH ACCOUNT OF THE TRAJECTORY

A model of satellite communication channel taking into account the trajectory, specifically developed for low Earth orbit satellite constellations, is presented. Low and high orbits have different advantages and limitations. To efficiently utilize resources in low Earth orbit satellites, it is necessary to forecast changes in the energy potential and adapt the parameters of satellite modems. For this purpose, there are such programs as Computer-Aided Design (CAD) "Albatross" for evaluating the dynamics of resource changes. However, a realtime model has been developed for the operational management of modems, allowing the construction of temporal diagrams depicting changes in the energy potential of communication channels. The development of such models can be performed in the LabVIEW environment, a software developed by National Instruments for creating virtual instruments (VIs). The development process includes considering the motion of the satellite in a user-defined orbit, taking into account various parameters. SubVIs are used to simplify program creation, improve code readability and enable element reuse. To construct one orbit the number of iterations in the loop is calculated, which is the rounded value of the orbital rotation period divided by the time difference between the calculated sub-satellite points. The smaller the value of the time difference is, the more accurate the trajectory will be. Constructing a trajectory with a larger number of revolutions requires more time. For performing the energy calculation, the antenna pattern (AP) is calculated, and a satellite trajectory is constructed with the cross-section of the antenna pattern on Earth. The developed model allows evaluation of the satellite trajectory for a given number of revolutions around the Earth and conducting energy potential calculations for a specified location of the Earth station. The results can be used for building algorithms for adaptive control of parameters in satellite radio links.