Radio Visibility Research Articles

Application of focusing systems to the protection of information during data transmission in the zone of direct radio visibility

Application of focusing systems to the protection of information during data transmission in the zone of direct radio visibility

Геометрический фактор односпутниковой системы определения местоположения абонентских терминалов по оценкам частоты доплеровским методом

The article presents a mathematical description of the doppler method of satellite communication systems user terminals geolocation by a retransmitted signal, as well as an analytical expression of the geometric factor of determining the location of user terminals. The analysis of the geometric factor distribution on the Earth's surface in the radio visibility zone of the repeater satellite is carried out.

New approaches to the development of information security systems for unmanned vehicles

<span>A new approach to ensuring information security is proposed for using in the zone of direct radio visibility. The approach is based on a direct analogy between radio and optical radiation. In the latter case, information protection can be ensured by identifying the point or direction from which the signal comes; all other light sources are cut off by the observer. It is shown that a similar method of information protection can also be implemented in the radio range, which corresponds to modern trends in the development of radio holography. The simplest scheme for detecting the direction to a transmitter, identified as “friend” is presented. Its operability is demonstrated by means of simulation modeling. Ways for the further development of this approach are determined, based on the fact that modern technologies make it possible to implement distributed reception of a radio signal (to use a relatively large number of receivers), which makes it possible to implement direct analogues of such optical elements as a lens, holograms.</span>

THE PROGRAM FOR ASSESSING THE CONNECTIVITY OF NODES OF WIRELESS EPISODIC NETWORKS UNDER THE CONDITION OF USING UAVS

Background. Based on analytical mathematical models, the duration of connectivity of mobile subscribers (nodes) (MS) of a wireless episodic network (WEN, consisting of MS and UAV) was investigated in conditions of direct radio visibility and considering the relaying.
 Objective. The purpose of the work is to find methodological approaches to ensure the connectivity of WSN nodes, which is a necessary condition for obtaining information from WSN in the absence of communication infrastructure.Methods. Simulation modelling based on MAPLE 14 software package and analytical calculation methods are used.
 Results. It is shown that the duration of connectivity is directly proportional to the size of the coverage area and inversely proportional to the movement speed of nodes. The mobility nature (scenario) of nodes also affects the duration of connectivity. The simulation of the nodes' movement was carried out under 4 scenarios: "march", "incoherent", "random wandering in the field" and "random wandering in the city". The largest values of the connectivity duration correspond to the third scenario, and the smallest - to the second (with a fixed radius of the coverage area and the movement speed of nodes). Thus, the average connectivity duration of the UAV-pedestrian connection in the event of an "incoherent" will be about 36 minutes, and the UAV-car connection - about 5 minutes.
 Conclusions. The system and functional parameters of the networks, which were obtained as a result of the research, will form the basis of the initial data and limitations of the mathematical model, and will also make it possible to determine the initial placement of the UAV network at the planning stage.

A method for estimating the linear velocity of a mobile object by a passive radar technical means outside the direct radio visibility zone

A method for estimating the linear velocity of a mobile object by a passive radar technical means outside the direct radio visibility zone

Adaptive analytical ray tracing of black hole photon rings

Recent interferometric observations by the Event Horizon Telescope have resolved the horizon-scale emission from sources in the vicinity of nearby supermassive black holes. Future space-based interferometers promise to measure the ''photon ring''--a narrow, ring-shaped, lensed feature predicted by general relativity, but not yet observed--and thereby open a new window into strong gravity. Here we present AART: an Adaptive Analytical Ray-Tracing code that exploits the integrability of light propagation in the Kerr spacetime to rapidly compute high-resolution simulated black hole images, together with the corresponding radio visibility accessible on very long space-ground baselines. The code samples images on a nonuniform adaptive grid that is specially tailored to the lensing behavior of the Kerr geometry and is therefore particularly well-suited to studying photon rings. This numerical approach guarantees that interferometric signatures are correctly computed on long baselines, and the modularity of the code allows for detailed studies of equatorial sources with complex emission profiles and time variability. To demonstrate its capabilities, we use AART to simulate a black hole movie of a stochastic, non-stationary, non-axisymmetric equatorial source; by time-averaging the visibility amplitude of each snapshot, we are able to extract the projected diameter of the photon ring and recover the shape predicted by general relativity.

Field of the atmospheric water vapor as a characteristic of heat and dynamic processes at the ocean surface observed by the microwave radiometric means from space

An approach to indication and analysis of heat and dynamic processes at the ocean surface and in the atmosphere with the methods of satellite passive microwave radiometry is considered. It bases on a responsiveness of the oceanic and atmospheric up-going microwave radiation to these processes in the spectral band of its attenuation in the atmosphere water vapor, which seems to be as kind of window of the "radio visibility" from satellites. The effectiveness of that approach is caused by the fact that atmospheric water vapor is an active participant (agent) in its heat interaction with the ocean surface and, at the same time, serves as its reliable quantitative indicator. Measured from satellites, natural microwave radiation of the atmospheric water vapor gives distinct signals of changes occurring in the frontal, storm and cyclonic zones in the ocean; they are manifested in the form of pics or jumps of the brightness temperature. The paper provides various examples of the study of such processes as the ocean-atmosphere heat interaction at the middle latitudes of the North Atlantic, origination and propagation of the tropical hurricanes in the Gulf of Mexico and Caribbean Sea, atmospheric water vapor transport in the tropical Atlantic and its influence on cyclogenesis in the Gulf of Mexico, etc. The data of satellite, ship and buoy measurements are widely used to attain and verify results of our study.

Метод оцінки зв’язності вузлів бездротових епізодичних мереж за умови застосування безпілотних літальних апаратів

The paper considers a method for assessing the connectivity of nodes of wireless episodic networks (WEN) under the condition of using unmanned aerial vehicles (UAVs). It is proposed to perform an evaluation of the connectivity of a pair of nodes according to a method, which is based on: an evaluation of geometric connectivity, which is limited to the maximum range of radio visibility at the physical level and the vulnerability interval of a given multiple access protocol at the channel level; assessment of information connectivity, which takes into account the presence of not only a physical connection of a given reliability, but also the presence of a free channel resource, a given amount of transmission delay at a given traffic limit value; assessment of the duration of connectivity taking into account the mobility of network nodes. On the basis of analytical mathematical models, the duration of connectivity of mobile subscribers (nodes) (MS) of the WEN consisting of MS and UAVs in direct radio visibility conditions and taking into account relaying was investigated. The connectivity of a pair of nodes is determined by the characteristics of different levels of OSI information interaction, such as radio range, channel bandwidth, information transmission delay, etc. It is shown that the duration of connectivity is directly proportional to the size of the coverage zone and inversely proportional to the speed of movement of nodes. The nature (scenario) of node mobility also affects the duration of connectivity. The simulation of the movement of nodes was carried out under 4 scenarios: «march», «skirmish», «random wandering in the field» and «random wandering in the city». The largest values of the duration of connectivity correspond to the third scenario, and the smallest to the second (with a fixed radius of the coverage area and the speed of movement of nodes). Thus, the average connection duration of the UAV-pedestrian connection in the event of a «difference» will be of the order of 36 minutes, and the UAV-car connection of the order of 5 minutes. The obtained results can be used in the UAV network topology control method.

The regional nanosatellite constellation modelling formation by a piggyback launch from different spaceports

The roadmap for constructing a regional nanosatellite constellation using the piggyback launch according to Chinese provider information has developed. For nanosatellite constellation formation to a specific purpose, it is necessary to analyse existing constellation operated similar tasks. Therefore, the software module for the Spire Global constellation orbital construction analysis was developed. The construction of Spire Global nanosatellites constellation based on orbital parameters database in the two-line element set format, satellite constellation databases and the developer site was analysed. A launch from the International Space Station and a piggyback launch were used for constellation formation. Nanosatellite deployment schemes, orbital parameters and flight parameters are investigated launches from the Taiyuan and Jiuquan Satellite Launch Centers with orbit inclination about 90°, that best correspond to the passes over Minsk (ϕ = 53°54′27″ N, λ = 27°33′52″ E) are analysed. The method of nanosatellite orbit preflight prediction at a passing launch has been developed. It involves a finding the nanosatellite state vector in the first flight day and at the time of constellation mission operate start. The launch time, satellite launch center coordinates, launch vehicle type, orbit inclination and altitude (period) are used in the method. In addition, the launch history and the satellite motion dynamics analysis on similar orbits is carried out. It was found that five launches are enough to organise a regional nanosatellite constellation with average radio visibility interruption time of at least 36 min with a maximum value of 85 min.

Development of methodological principles of routing in networks of special communication in the conditions of fire damage and radio electronic flow

The object of research is a system of special communication. Decision making support systems (DMSS) are actively used in all spheres of human life. They are especially common in the processing of large data sets, forecasting processes, providing information support in the decision-making process by decision-makers. Systems of analysis of information transmission in special purpose radio communication systems are no exception. However, there are a number of problems in the transmission of information, namely: the transmission of information takes place in a complex electronic environment against the background of intentional and natural interference; elements of the radio communication system are the objects of primary fire damage due to high radio visibility for radio intelligence. The best solution in this situation is to integrate with the data of the information system analysis of the electronic environment, artificial neural networks and the ant algorithm. Their advantage is also the ability to work in real time and quickly adapt to specific situations. Therefore, in this paper the methodological principles of routing in special communication networks in the conditions of fire damage and electronic suppression are developed. Improving the efficiency of information processing (reducing error) evaluation is achieved through the use of evolving neuro-fuzzy artificial neural networks; learning not only the synaptic weights of the artificial neural network, but also the type and parameters of the membership function. Efficiency of information processing is also achieved through training in the architecture of artificial neural networks; taking into account the type of uncertainty of the information to be assessed; synthesis of rational structure of fuzzy cognitive model. It reduces the computational complexity of decision-making; absence of accumulation of an error of training of artificial neural networks as a result of processing of the information arriving on an input of artificial neural networks. The approbation of the use of the offered technique on the example of the estimation of information transfer in the conditions of influence of destabilizing factors is carried out. This example showed an increase in the efficiency of evaluation at the level of 15–25 % on the efficiency of information processing.

Development of a rangefinding method for determining the coordinates of targets by a network of radar stations in counter-battery warfare

The increase in the accuracy of determining the coordinates of targets is explained by the use of a network of counter-battery radar stations and the rangefinding method for determining the coordinates of targets. The main advantage of using the rangefinding method for determining the coordinates of targets in a network of counter-battery radar stations is to ensure the required accuracy in determining the coordinates of targets without using accurate measurement of angular coordinates. The minimum geometry of the system, which ensures the use of the rangefinding method for determining coordinates, is given. The method of determining the coordinates of targets by a network of counter-battery radar stations has been improved. In contrast to the known ones, information about the range to the target is additionally used in a spatially distributed network of radar stations for counter-battery combat. The boundaries of the working zones of the network of two and three counter-battery radar stations are calculated. The features of creating a continuous strip using the rangefinding method for determining the coordinates of the target are considered. Statistical modeling of the rangefinding method for determining the plane coordinates of the target has been carried out.
 It has been established that the use of the rangefinding method ensures the determination of the planar coordinates of the target in a sector of at least 120°. The targets are at a distance of direct radio visibility in relation to the counter-battery radar. The root-mean-square error in determining the target range in this case is no more than 50 m. It has been established that the creation of continuous bands of a low-altitude radar field at a certain height is possible by arranging radar stations in a line. In this case, the distance between the counter-battery radar stations should be no more than half the target detection range at this height

Development of methodological principles of routing in networks of special communication in conditions of fire storm and radio-electronic suppression

Decision making support systems are actively used in the processing of large data sets, process forecasting, providing information support to the decision-making process by decision-makers. However, there are problems with the transmission of information: the transmission of information takes place in a complex electronic environment against the background of interference; radio communication systems are the objects of primary fire damage due to high radio visibility. This article develops the methodological principles of routing in special communication networks in the conditions of fire damage and electronic suppression. The purpose of this research is to increase the efficiency of information transfer under the influence of destabilizing factors. The proposed methodological principles are based on the theory of artificial intelligence. The research presents a mathematical formulation of the problem of routing in special-purpose radio networks and developed a method of routing in special-purpose radio networks.
 The efficiency of information processing is achieved through training in the architecture of artificial neural networks; taking into account the type of uncertainty of the information to be assessed; use of the ant algorithm. The approbation of the use of the offered technique on the example of the estimation of information transfer in the conditions of influence of destabilizing factors is carried out. The proposed methodological principles should be used in the development of software for programmable devices of communication and in the modernization of existing and development of new radio communication devices. This example showed an increase in the efficiency of information transmission in radio communication systems at the level of 15–25 % on the criterion of efficiency

Method for calculating the duration of communication sessions with a spacecraft under constraints of the communications coverage of the command and tracking station

Consideration is given to a method for calculating the duration of communication sessions of the command and tracking station with a spacecraft, which enables to make an efficient use of the session time when planning control operations in order to avoid their premature performance or contingency termination in the event of constraints in the ground site coverage. Thanks to the developed method, it was possible to identify communication coverage with limited radio visibility and exclude the times of constraints from the total session duration providing a zone of stable radio exchange with SC while performing control operations, thereby increasing reliability of their performance in the communication session. The method was successfully applied in control of the Resurs-P SC constellation, where it demonstrated its capabilities and efficiency. It can be used to control other advanced SC. Key words: spacecraft, ground control complex, flight planning, session control operations, spacecraft motion model, numerical integration method.

Methodology of Parameters Calculation for a Series of ‘‘Major’’ Trajectory Corrections of the Spektr-RG Spacecraft to Improve Its Radio Visibility

Methodology of Parameters Calculation for a Series of ‘‘Major’’ Trajectory Corrections of the Spektr-RG Spacecraft to Improve Its Radio Visibility

ИМИТАЦИОННОЕ МОДЕЛИРОВАНИЕ СПУТНИКОВОЙ СИСТЕМЫ СВЯЗИ С ИЗМЕНЯЕМОЙ ОРБИТАЛЬНОЙ СТРУКТУРОЙ

Introduction. The article is a logical continuation of the authors' work on the study of the effectiveness of the inclusion of the space segment, in particular the satellite communication system, in the control loop of the aircraft. The satellite communication system allows you to provide a radio signal coverage of a given territory at any time. This can be both local and global coverage of the globe. Methods. However, it is necessary to find such a structure and parameters of the orbits of the grouping of the communication and data relay system as the main structural and functional element for transmitting control commands that will ensure the effective performance of the control and guidance tasks in flight at any time in any environment. In the article, expressions are obtained for calculating the radio visibility time of the studied objects during the movement of a mobile target, and an expression is derived for calculating the probability of bringing control information to the aircraft during its flight. The analysis of the main characteristics that determine the quality of object management is given. Due to the high complexity, and sometimes impossibility, of calculations and the stochastic nature of both the process itself and the influencing factors on the aircraft, the study suggests using the simulation method as a tool for calculating the quantitative characteristics of the objective function – the probability of delivering command and control information from the com& mand post via a satellite communication system to the means of delivery and defeat for the implementation of correction of the incoming trajectory and following the movement of the mobile target. The analysis and conclusion of the outcome modeling operators and the evaluation of the efficiency indicator are given. And also a look at the application of such a method of statistical tests as the Monte Carlo method in simulation modeling is given. The general relations for this method are given, its positive aspects and the essence of its application in the study of finding a variant of the strategy for using a satellite communication system are considered, as well as the justification of a suboptimal variant of the composition, structure and characteristics of the orbital grouping under study in relation to the specifics of the process of targeting a delivery vehicle and hitting a mobile target.

АНАЛІЗ КОСМІЧНИХ СИСТЕМ ВИЯВЛЕННЯ РУХОМИХ НАДВОДНИХ ОБ’ЄКТІВ

In the context of Russian Federation aggression against Ukraine, there is an urgent need to increase the number of sources of reliable information about mobile water surface objects in the Black Sea and the Sea of Azov. Space systems for mobile water surface objects monitoring should be considered as sources of relevant information. This is due to the fact that space systems make it possible to quickly detect, identify and observe mobile water surface objects under various weather conditions at a distance that far exceeds the range of radio visibility between the data reception point and the observation object. Also in this case, there are no threats to the life and health of the system operator. The use of space systems in the system of monitoring of mobile water surface objects in the interests of the security and defense sector of Ukraine will contribute to achieving the rates specified in the National Security Strategy of Ukraine, Military Security Strategy of Ukraine, Strategic Defense Bulletin, Strategy of the Naval Forces of the Armed Forces of Ukraine 2035, Visions for the Ukrainian Navy 2035, Visions for the Development of the Armed Forces of Ukraine 2030. In particular, it is expected to increase the capabilities of the Navy, provided by a single list (catalog) of capabilities of the Ministry of Defense of Ukraine, the Armed Forces of Ukraine and other defense forces. In addition, the successful solution of the task of receiving data on mobile water surface objects from space systems will contribute to the development of Ukraine as a space state. Further research on the selected topic will focus on the possibility of creating a universal automated system for receiving data from space systems for monitoring mobile water surface objects. It is also possible to study the issue of receiving data from space systems on the geospatial position of mobile objects in the airspace and on the ground.

Development of mobile aircraft control system model with additive technologies

The article describes the parameter evaluation of mobile spacecraft control systems and identifies their main advantages in comparison with stationary assets. The model and the mobile spacecraft control system mock-up using additive technologies were developed with existing methods for prototyping complex technical systems. This model performs experimental operations of the prototype of the mobile control system, accompanies the spacecraft in the area of its radio visibility, simulates the implementation of technological cycles of spacecraft control, evaluates the parameters of the target equipment, analyzes the characteristics of the antenna system and the layout, conducts experiments and eliminates abnormal situations. It also optimizes the spacecraft testing based on the use of artificial intelligence techniques.

Microstrip antenna array with an inclined surface and an increased distance between patches

A new technique for designing a path antenna array with an inclined beam is proposed. It boils down to finding a certain combination of parameters that use the secondary main maxima of the diagram as the main beam and at the same time guarantee the greatest distance between the emitters that does not yet lead to the occurrence of secondary main maxima in the antenna radiation pattern. This simplifies the geometric structure of the antenna, reduces its cost, simplifies the microstrip power system, and reduces the mutual influence of individual elements in the antenna array. To combine the possibility of reducing the radio visibility of the antenna by changing the orientation of the antenna opening while maintaining its emissivity in a given viewing plane, it is possible to implement an antenna with a main beam deviated from the normal. The efficiency of reducing backscattering for the radar range due to the tilt of the antenna outside the operating frequency band of the antenna is investigated. Thus, when mechanically scanning the antenna, due to the fact that the main beam of the antenna array is deviated from the normal, it is possible to achieve a significant reduction in the average backscattering pattern of at least 25 dB. It is known that improving the safety of small aircraft at low altitudes, as well as on take-off and landing sites, is directly related to the introduction of a small weather radar, which warns of the presence of dangerous phenomena along the flight path: thunderstorms, turbulence, and wind. When the onboard radar is operating in thunderstorm or turbulence detection modes, the presence of re-reflections from the Earth's surface can lead to the formation of false areas that are dangerous for flight. You can reduce the likelihood of such false zones by spatial filtering of interference from the ground using antennas with a low level of side lobes in the lower hemisphere. The relevance of the problem of reducing the influence of interference from the ground on the correctness of the wind speed estimation in the weather radar is confirmed by publications. They are focused on filtering interference from the earth's surface in the frequency domain for ground-based weather radars or for airborne radars, but by the main beam of the alignment diagram and the rule of its elevation to avoid touching the ground. The second part of the research is devoted to reducing the influence of re-reflections from the earth on the probability of forming false areas of dangerous weather events in the weather radar. To reduce the impact of interference, it is proposed to install an antenna with an upward tilt.

Technical aspects of creating radiotechnical systems of information and command interface to ensure the functioning of complexes with unmanned aerial vehicles

One of the key components of the complexes with unmanned aerial vehicles (CUAV), which significantly affects the safety and reliability of operation, is the radio link for transmitting command-telemetric and target information of direct radio visibility (radio engineering system of information and command interface) between unmanned aerial vehicles (UAV) and the ground control and information processing point (GCSP). Heavy-class unmanned aerial vehicles can have several target loads simultaneously – a multispectral optical-electronic system, a digital aerial photo system, a radar system, a radio monitoring system, etc. Due to the fact that the flow of information with the payloads to the input of the radio link during peak time moments can be quite large, severe requirements are imposed as to the equipment of primary processing of the target information aboard the UAV and it’s compression in the recording information, and the bandwidth of the radio link in terms of transmission target information on GCSP for subsequent analysis and processing by the operator of the complex. Technical articles are the justification of modern approaches to the development of radio systems of information and team mates in the functioning of complexes with unmanned aerial vehicles, modeling and analysis of directional properties of the antenna system on the basis of the active phased array antenna (APAA) to ensure that decisions adopted targets CUAV, calculation and modeling of the use of various signal-code structures in the information and command-telemetry channels of the CUAV in order to assess the achievable data transfer rates and the energy budget of radio lines. The main tasks of the article are consideration of the nomenclature of possible target tasks of complexes with UAV, proposals for the technical implementation of radio systems of information and team mates, analysis of the advantages of using APAA as part of an unmanned aerial vehicle and a ground control and information processing point in order to improve the efficiency of UAV complexes in the end, modeling of directional diagrams in the azimuth and angular planes for receiving and transmitting modules and receiving and transmitting panels from the APAA, calculation of the energy budget of information and command radio lines, plotting the dependences of the error probability on the signal-to-noise ratio for various combinations of signal modulations and noise-tolerant encoding for various models of communication channels (additive white Gaussian noise – AWGN and binary-symmetric channel – BSC). The main results of the article include specific practical suggestions and recommendations on hardware and software approaches to the creation of antenna systems based on APAA as part of the CUAV, the effect of using modern approaches (reliability, reduced labor intensity and cost, improved performance characteristics), calculated signal-to-noise ratios for various methods of modulation and encoding, obtained as a result of calculations and mathematical modeling, as well as suggestions and recommendations for the rational use of specific types of signals and codes in the command-telemetry and information channels.

Decision Routing Problems in A Wireless Sensor Network Based on A Neural Mechanism

This article proposes a solution for the routing problem in wireless sensor networks (WSN) based on a neural mechanism. The basic concepts of wireless sensor networks, artificial neural networks (ANNs), and WSN routing protocols are presented. The Kohonen ANN was selected to solve the problem of routing in wireless sensor networks based on a neural mechanism. A radio visibility matrix is proposed, which is a mathematical description of the connectivity of network nodes and the radio visibility of each node with respect to all other network nodes. Based on the Kohonen ANN trained by the constructive method, a method for WSN neural network clustering was developed. Two software-modeling environments are presented that were created to confirm the theory with respect to the logic of the developed methods for WSN clustering, their correction and the verification of their adequacy. Numerical results of modeling the solution of the routing problem in a wireless sensor network based on a neural mechanism by neural network clustering, the WSN matrix clustering method and the energy distance neural clustering protocol (EDNCP) are presented. It was found that the developed EDNCP protocol was 29% more efficient than known analogs.