Geostationary Communication Satellite Research Articles

Measuring the difference in gravitational potentials of ground points using the duplex satellite method

The issue of measuring the difference in gravitational potentials and the corresponding difference in orthometric heights based on two spatially separated highly stable ground-based hydrogen quantum clocks is investigated. The relevance of the presented study and its practical significance are determined, in particular, by the prospects for measuring the difference in orthometric heights using the duplex method of comparing the time scales of remote consumers via a geostationary communications satellite. The problem of determining the difference in gravitational potentials and the corresponding difference in orthometric heights between points on the Earth's surface is considered. A solution is proposed for measuring the difference in orthometric heights using the duplex method of comparing time scales of remote consumers via a geostationary communications satellite. A scheme of an original experiment is described for measuring the difference in gravitational potentials and the corresponding difference in orthometric heights based on two spatially separated highly stable ground-based hydrogen quantum clocks. In accordance with the proposed scheme, for the first time in the Russian Federation, the difference in gravitational potentials and orthometric heights of ground points located at a distance of 825 m from each other was measured based on the duplex satellite method and transportable quantum hydrogen clocks. The domestic geostationary satellite Express-80 was used in the geostationary repeater satellite; duplex communication was established using stationary and relocatable sets of duplex equipment. With a relative instability of quantum clocks of 10–15 and a difference in orthometric heights of about 21 m, the measurement error was 2.8 m. The results obtained are relevant for geodetic gravimetry when solving problems of constructing a unified altitude base using highly stable quantum frequency standards.

Proof-of-Concept Real-Time Implementation of Interleavers for Optical Satellite Links

Ground-satellite optical links are a promising technology for increasing capacity and security over radio frequency links, while reducing weight and power consumption. However, atmospheric turbulence generates power fadings at the reception terminal. This effect can be mitigated by combining adaptive optics, forward error correction and data interleaving. While adaptive optics has been extensively studied, forward error correction together with long interleaving (e.g., multiple 10 ms) has not yet been demonstrated in this context. In this article, we present a proof of concept of an optical satellite uplink, precompensated by adaptive optics, which leverages a long interleaver in an external memory and operates at 10 Gbps with SFP+ transceivers. We account for the issues associated with real-time implementation and interfacing to a high-speed memory. To validate our proof of concept, we generate time-series for a typical ground to geostationary satellite communication link, using a field-validated simulator. Using these time series, we calculate the required interleaver time as a function of the launch power. Finally, we show the impact of different transmitter pupil diameters and of different wind speed profiles, on the interleaver duration.

Frequency-Selective Beam-Shaping Technique to Provide Equal Beam Coverage Using Reflectarray Antennas for Dual-Band Multispot Satellites

In this communication, a simple technique is presented for transmit/receive (Tx/Rx) reflectarrays in the Ka-band to improve the shaping of the Rx beams without altering the performance in Tx, with application to geostationary satellite communications. The technique is based on the introduction of a controlled phase noise in the reflected field at Rx frequencies by a 180° phase reversal gradually introduced in some reflectarray cells randomly distributed on the antenna. Simulations of a 1.8 m parabolic reflectarray at 19.7 and 29.5 GHz show a reduction of 2.6 dB in the roll-off factor at 29.5 GHz, with also lower sidelobe levels. The proposed solution offers a large flexibility to shape the beams by a simple method with a low computational cost that does not increase the manufacturing complexity and costs of the antenna.

Computational and experimental study of an ion injector of a weakly divergent ion beam for implementing a method for removing space debris objects by an ion beam

Attention to the method of removing large space debris objects by impacting them with an ion beam has not waned over the past 10 years. The application of this method to the space debris removal from the protected area of the Geostationary Earth Orbit (GEO) seems to be the most effective. This is due to a low energy consumption for removing an object to a safe orbit with ΔV≃11 m/s, which allows the removal of several objects by a single spacecraft. A service spacecraft can be developed for this purpose based on the TelSat geostationary communication satellite technology. At the same time, one of the problematic issues remains that is the development of an injector of a weakly divergent ion beam. The ion beam divergence during injection into the vacuum occurs under the insuperable influence of the ambipolar electric field acting in the beam volume. At the same time, the beam behavior depends on the initial divergence angle stipulated by the conditions of beam formation by the electrostatic acceleration system. This paper considers the results of calculated and experimental studies for the peculiarities of the formation of an ion beam in an ion extraction system with slit and round apertures. The dependence of the initial divergence half-angle on the beam perveance for both geometries was defined. In the operation of the injector designed for the space debris removal, it is necessary to ensure stability of the geometry of the ion-extraction system, which is subject to uneven thermal loading. The resulting thermomechanical deformations of the grids in the technology of ion thrusters are parried by giving the grids a plate shape. Therefore, flat grids made of a carbon-carbon composite material of a new type were used in experiments, which avoided noticeable deformations. The results of experimental investigation of the prototype of ion injector with two configurations of carbon grids (with round and slit perforation) and with the initial divergence half-angle of 2°-4° are given in this paper. The thrust control of an ion beam by changing of the screen grid potential under the condition of a constant beam perveance is considered. It is shown that such regulation is associated with a change in the Mach number, which affects the beam divergence. As an example, the calculation of the dependence of the coefficient k on the distance to the removing object is given, which is considered to be a spent satellite SUPERBIRD-A.

A Beam Search-Based Channel Allocation Method for Interference Mitigation of NGSO Satellites with Multi-Beam Antennas

In the past few years, non-geostationary orbit (NGSO) satellite communication constellations have regained popularity due to their conspicuous advantages. Nevertheless, with more NGSO satellites getting involved in communications, the spectrum resources should become much more scarce. Multi-beam high throughput satellite and spectrum sharing are two major techniques in communication design. The two techniques can significantly mitigate interference and highly augment the capacity of the communication system. Thus, they are commonly used in satellite communication systems nowadays. With a massive number of NGSO satellites comprising the communication system and moving in their orbits, interference scenarios are pretty complex. In this article, the relationship between the level of interference and the beam distance is deduced. Moreover, for beams with different tilting angles, the different off-axis angles may correspond to the same beam distance, which is directly related to the interference level. Through the interference analysis, we propose a channel allocation method that uses a beam search algorithm to optimize the channel allocation problem and achieves outstanding time efficiency. The performance of the proposed method is validated by a coexisting scenario of the geostationary orbit and NGSO satellite communication systems. The results show that the level of interference can be largely mitigated, and the capacity of communication systems is significantly augmented.

Communication satellite resource scheduling based on improved whale optimization algorithm

Under the background of increasing pressure of satellite communication support, reasonable and efficient dispatch of communication satellite resources is an important means to improve the utilization efficiency of communication resources. Aiming at the resource scheduling task requirements of geostationary orbit communication satellite system, communication satellite resource scheduling (CSRS) model is established first of all, based on this, advances a kind of CSRS method based on improved whale optimization algorithm. In this method, the detection and search strategy is proposed and the crossover mutation operator is used to avoid the algorithm falling into local optimum. Simulation results show that IWOA can effectively improve the quality and stability of satellite resource scheduling.

РОБАСТНОЕ УПРАВЛЕНИЕ КОСМИЧЕСКИМ РОБОТОМ-МАНИПУЛЯТОРОМ ПРИ ОБСЛУЖИВАНИИ ГЕОСТАЦИОНАРНОГО СПУТНИКА СВЯЗИ

Methods have been developed for robust control of a space robot-manipulator during the in-flight maintenance of a geostationary communications satellite – replacement of fuel tanks, solar array panels and other replaceable components of the satellite attitude and orbit control system, which leads to significant changes in the inertial parameters of the hard clutch of a space robot with a geostationary satellite. The results of computer simulation for typical dynamic processes at such maintenance of a geostationary communications satellite are presented.

Resource management of GEO relays for real-time remote sensing

Remote sensing is one of the main applications of satellite communication. With limited communication time between low earth orbit (LEO) sensing satellites and the ground, geostationary orbit (GEO) satellite relaying has become an effective solution. In practical applications, one GEO communication satellite usually needs to provide data forwarding services for multiple satellites or even multiple satellite constellations. Therefore, communication resource management of GEO satellites has become crucial. Existing methods only focus on resource allocation without taking data forwarding task scheduling into consideration, which limits their applicability in real-time applications. In this paper, we propose a real-time resource management approach for GEO relaying, aiming to maximize network throughputs as well as to reduce transmission delays. In this approach, resource allocation is modeled as a Stackelberg game while task scheduling is modeled as a real-time queuing problem. Furthermore, we propose two real-time algorithms, including an adaptive gradient descent method to find optimal price for data forwarding services with low computational complexity, and a queue-jumping algorithm for data forwarding scheduling to minimize transmission delays. With comparison with existing methods, simulations verify the effectiveness of our proposed method with respect to convergence speed of the algorithm, network throughputs, and transmission delays.

LEVERAGING SYNERGETIC INFORMATION RESOURCES FOR ANGULAR MOTION CONTROL OF UNMANNED SPACECRAFT

A key condition for accomplishing a mission of an unmanned spacecraft consists in providing it with resources. Resources can be replenished through synergetic observations of processes in cases where measured data are partially or fully missing or lacking for some of the controlled objects by means of measuring parameters of the processes characterizing the operation of other controlled objects. As an example, the paper discusses provisioning of resources for the process of controlling the motion about the center of mass by means of synergetic observations in cases where no inertial instrument was available for measuring the angular rate vector in the system controlling the motion of the geostationary communications satellite Yamal-200. Specifically, the observation is based on the operation of transitive closure of the binary relation defined on the base set of processes in the onboard systems and ground assets for radio interactions with the onboard systems of the unmanned spacecraft. Key words: unmanned spacecraft, control process, measuring data, binary relations, transitive closure, provision of resources.

Leveraging synergetic information resources for angular motion control of unmanned spacecraft

A key condition for accomplishing a mission of an unmanned spacecraft consists in providing it with resources. Resources can be replenished through synergetic observations of processes in cases where measured data are partially or fully missing or lacking for some of the controlled objects by means of measuring parameters of the processes characterizing the operation of other controlled objects. As an example, the paper discusses provisioning of resources for the process of controlling the motion about the center of mass by means of synergetic observations in cases where no inertial instrument was available for measuring the angular rate vector in the system controlling the motion of the geostationary communications satellite Yamal-200. Specifically, the observation is based on the operation of transitive closure of the binary relation defined on the base set of processes in the onboard systems and ground assets for radio interactions with the onboard systems of the unmanned spacecraft. Key words: unmanned spacecraft, control process, measuring data, binary relations, transitive closure, provision of resources.

Research of the ranges of effective application of unified space platforms for geostationary communication satellites

The topical problem of choosing the standard size of the unified space platform developed by the joint-stock company «Academician M. F. Reshetnev» Information Satellite Systems» for geostationary communication satellites has been formulated. Previously, the task of assessing the effectiveness of using the developed unified platforms for creating a new spacecraft was solved to a greater extent empirically, by generalizing the groundwork for existing developments and assessing the possibility and feasibility of using the existing groundwork in the future (development continuity). However, a methodological basis for solving this kind of problem has not yet been developed. As part of the study, a model for assessing the efficiency of a spacecraft based on a unified space platform was developed. A method for evaluating the effectiveness of the use of unified space platforms with an excess resource (in terms of mass and energy consumption) for the payload and a method for evaluating the effectiveness of using a modernized unified space platform, which makes it possible to meet increased resource requirements (in terms of weight and energy consumption) for the payload, have been developed. With the help of the developed methods, the assessment of the range of effective use of a unified space platform for geostationary communication satellites developed by JSC ISS was carried out, both without revision and with the necessary modernization for a specific project (payload).

Comprehensive use of IT solutions to monitor the state of construction sites

The work examines new IT - solutions for monitoring the state of construction projects. Two areas are investigated: the first - monitoring of high-rise buildings and other large-scale objects, the second - monitoring of construction sites located in remote, hard-to-reach areas. The possibilities of integrated use of the following information technologies are considered: Machine Vision, Wireless Sensor Network WSN, Edge Computing. Other new IT solutions are also in the field of view of the study: Cloud Computing, the Internet of Things, etc. To improve the quality of monitoring, it is proposed to use advances in other subject areas - in the field of unmanned aerial vehicles (drones) and in the space area (geostationary satellite communications). The idea of using drones and artificial earth satellites to monitor objects (particularly buildings) is not new in itself, but the use of these devices as part of the proposed set of IT technologies allows to bring solutions in the construction industry to a qualitatively higher level.

Управление пространственным движением геостационарного спутника связи в режиме длительной консервации

Methods for analyzing the spatial motion of a satellite in geostationary orbit in the mode of long-term conservation with occasional activation of the control system are developed. The computer simulation results of a geostationary communication satellite motion during the year with quarterly correction are presented.

Ranging technology using signals of opportunity of non-cooperative communication satellites

AbstractThe positioning technique employing the ubiquitous signals of opportunity of non-cooperative satellites does not send special navigation signals, instead it passively receives satellite signals as noise, presenting advantages of concealment and difficulty for potential attackers. Thus, this study investigates the ranging principle and model using non-cooperative communication satellites and a time difference estimation algorithm. The technology of time difference measurement under non-cooperative observation mode was determined and simulated. A test platform for time difference measurement was built to receive the signal from an unknown geostationary Earth orbit communication satellite and verify the ranging feasibility and performance. The ranging accuracy was found to be smaller than 6 m, as demonstrated by experimental data, which shows the viability of the proposed positioning technique for ranging technology.

Geostationary Communication Satellite Solar Array Optimization Using Gravitation Search Algorithm

The preliminary design of geostationary communication satellite solar array is presented in this work. Based on the power requirements, power margin requirements and performance requirements, the number of panels, strings and cells to be used on the solar array were defined. The main objective of this study was to optimize the power generated from the satellite solar array and the extraction of the parameters of a photovoltaic module, which is subject to the space environment and under a series of practical constraints, in order to extract the desired performance parameters for multiobjective functions, taking into account the solstice and equinox periods during temperature operation. A gravitational search algorithm based on the law of gravity and mass interactions was introduced. This algorithm has proved its effectiveness in optimizing system parameters in the literature. From the results obtained in this work, the total power of the optimized system was reduced by 181 W. The degradation and output power characteristics of the solar panels were calculated for different temperature values.

Determination of Coverage Oscillation for Inclined Communication Satellite

The communication engineers need to evaluate footprint movement to deploy a ground station. Geostationary communication satellite’s inclination angle causes the movement of a satellite footprint. The calculation of the inclination angle requires complex astronomical knowledge and mathematical calculations. On the other hand, a satellite communication engineer does not need a very accurate inclination angle value to design a ground station for required service availability. We propose a practical method called trigonometric curve fitting for the inclination to solve the problem. The past and the future value of inclination can be evaluated by using the curve-fitting method. It is a simplified practical method and does not need advanced orbital dynamics knowledge. The orbit geometry and evaluated inclination angle are used for estimation of a coverage area movement. A satellite communication engineer can evaluate coverage area oscillation quickly and design a better link for an inclined orbit satellite by using the proposed method. We have evaluated the inclination angle of the communication satellite Sat-1 with the proposed method. Sat-1 spot beam movements and wide beam coverage area movements are estimated to obtain EIRP and G/T fluctuation for link budget purposes. The proposed method provides the results that are consistent with the results of measurements and the results of satellite operators’ professional tools.

Tunable RF Filters Based on Liquid Crystal for Space Applications

On board of communication satellites, there are numerous RF filters in the payload used for guiding wanted signals as desired and for rejecting unwanted signals such as not to interfere with wanted signals. At present, satellites have a long lifetime (15 years at least for a typical geostationary communication satellite) and there is also time elapsing between its design and the start of in-orbit service (2 years at least). On the other hand, conventional RF filters for satellite applications are fixed frequency. Therefore, there is a growing demand for in-orbit tunable filters to be able to cope with changes in the market situation during that long time. Also, there are communication systems evolving that rely on tunable devices used for adaptive filtering or steering. This article reports on in-orbit tunable bandpass filters employing liquid crystal material and operating at 20 GHz, and especially on design aspects dealing with the harsh space environment, on the operating principles for commanding the filters on board the satellite, and on a qualification campaign passed successfully. A demonstrator unit is in manufacturing for in-orbit verification.

Алгоритм расчета технического уровня системы геостационарной спутниковой связи

Алгоритм расчета технического уровня системы геостационарной спутниковой связи

Количественная оценка технического уровня космических систем дистанционного зондирования Земли и геостационарной спутниковой связи

Количественная оценка технического уровня космических систем дистанционного зондирования Земли и геостационарной спутниковой связи

Optimized Analytical Solution of Platform Panel Radiative Area Dimensioning of Geostationary Communications Satellites: A Practical Approach

Determining radiative areas of geostationary satellite are one of the challenging tasks for satellite thermal engineers at the early stage of the project. Radiative areas of geostationary communication satellite for the payload and platform panels are determined based on worst hot case (end-of-life). After calculation of radiative areas, it needs to be optimized according to worst hot and cold scenario at sun acquisition mode, orbit raising mode and geostationary orbit. In this study, geostationary satellite platform panel was considered. The radiator’s dimensions were calculated and then optimized based on sun acquisition mode, orbit raising mode and geostationary orbit. Calculated radiative areas both the north panel and the south panel was 1 m2. Radiative areas were studied at +/-10% m2. It was seen from the analytical results that the surface temperature of the platform panel areas were between -48.5 oC at 1.1 m2 of radiative area and 37.7 oC at 0.9 m2 of radiative area.