Vol 19, No 1 (2018)

The question of ensuring strength, durability and survivability of a spacecraft construction with mathematical mod- eling complexes is a modern trend in satellites design. This approach is based on the shortening of the prelaunch preparation stage. In particular, this is due to the reduction in the number of vibration tests of a spacecraft (SC). In the present work, using the example of vibration tests of “Express-1000K” service system module, we consider the verifica- tion technique for the mathematical model of communication satellites, output by a pair of payloads. The choice of this research object was caused by the conceptual scheme for modern space vehicles constructing, based on the modular principle. The service system module is the basic supporting structure of the spacecraft, able to integrate with any pay- load (information support, scientific research, geodesy and remote sensing, navigation) and is a universal tool in a sat- ellite construction. In tests with harmonic vibration, the first longitudinal and transverse tone of the spacecraft oscilla- tions are well identified, which can be fairly easily predicted applying the finite-element model. Proceeding from this, the accuracy of forecasts depends, to a greater extent, on the complexity of the modeled construction and the modeling procedure being used. The study provides a finite-element modeling technique for spacecraft output by a pair of pay- loads; the dynamic characteristics of the object of investigation by calculation and experimental methods are obtained. The identification procedure was carried out using the ‘modal consent’ method. The verification technique considered in the study makes it possible to carry out effective adjustment of the finite-element model. The finite-element model obtained by verification results allows to effectively evaluate the behavior of a spacecraft already at the design stage, which enables to shorten the time of vibration tests. The main results of this research were applied in verification of mathematical models of modern spacecraft developed by JSC “ISS”. The importance of applying verification methods of the mathematical model of the product at the preliminary (design) stage of spacecraft creation was noted.

The present paper describes an FPGA design of a camera-to-touchscreen demonstrator that has been prepared using Xilinx Vivado 2015.2 and SDK 2015.2 tools. The demonstrator consists of MicroZed 7020 Carrier Board, Avnet 7-inch Zed Touch Display and Avnet Toshiba Industrial 1080P60 Camera Module. The camera transmits a full HD video signal at 60 frames per seconds to MicroZed 7020 board, which processes it and sends to the LCD display with active area of 800×480 pixels. As the display has smaller resolution, only a fragment of the whole video frame can be seen at once on the display, whereas the full image is stored in the memory. By touching the screen one can travel along the stored video frame and look through the whole image. The design can be used, for example, as a car rear view mirror monitor benefiting from touchscreen technologies

This paper is devoted to the construction of a new class of models under incomplete information. We are talking about multidimensional inertia-free objects for the case when the components of the output vector are stochastically dependent, and the character of this dependence is unknown a priori. The study of a multidimensional object inevitably leads to a system of implicit dependencies of the output variables of the object from the input variables, but in this case this dependence extends to some components of the output vector. The key issue in this situation is the definition of the nature of this dependence for which the presence of a priori information is necessary to some extent. Taking into account that the main purpose of the model of such objects is the prediction of output variables with known input, it is necessary to solve a system of nonlinear implicit equations whose form is unknown at the initial stage of the identifica- tion problem, but only that one or another output component depends on other variables which determine the state of the object. Thus, a rather nontrivial situation arises for the solution of a system of implicit nonlinear equations under condi- tions when there are no usual equations. Consequently, the model of the object (and this is a main identification task) cannot be constructed in the same way as is accepted in the existing theory of identification as a result of a lack of a priori information. If it was possible to parametrize the system of nonlinear equations, then at a known input it would be necessary to solve this system, since in this case it is known, once the parameterization step is overcome. The main content of this article is the solution of the identification problem, in the presence of T-processes, and while the pa- rametrization stage can not be overcome without additional a priori information about the process under investigation. In this connection, the scheme for solving a system of non-linear equations (which are unknown) can be represented in the form of some successive algorithmic chain. First, a vector of discrepancies is formed on the basis of the available training sample including observations of all components of the input and output variables. And after that, the evalua- tion of the output of the object with known values of the input variables is based on the Nadaraya-Watson estimates. Thus, for given values of the input variables of the T-process, we can carry out a procedure of estimating the forecast of the output variables. Numerous computational experiments on the study of the proposed T-models have shown their rather high effi- ciency. The article presents the results of computational experiments illustrating the effectiveness of the proposed tech- nology of forecasting the values of output variables on the known input.

At present to transfer a spacecraft from a low earth to geostationary orbits propulsion systems of two types are most widely used: chemical and electric. Each type has its advantages and disadvantages. The application of any one of them does not always satisfy conflicting requirements. A possible solution may be the use of a combined propulsion system consisting of a chemical and electric propulsion system. This combination allows the spacecraft to be launched faster than using only electric motors, and it is more efficient in terms of the payload mass than using only a chemical propul- sion system. Electric propulsion engines (plasma or ionic) need energy sources. Usually, solar batteries are used for these purposes. The idea of using such a combined propulsion system, consisting of a solar electric propulsion sys- tem and the Fregat upper stage, was considered within the “Dvina TM” research project. The use of such a propulsion system requires, even at the design stage, to determine the parameters of the various types of engines that make up its structure. For a reasonable choice it is necessary to have information about the influence of the various propulsion system parameters on the final characteristics of the maneuver. When putting a spacecraft into orbit, it is necessary for the spacecraft to overcome Van Allen belts while the ele- ments of its design are subjected to intensive action of charged particles, which can significantly limit the period of ac- tive existence. Using a combined propulsion system, it is possible to shorten the time of being in a field of high radiation level significantly. The aim of the study was to synthesize a method for estimating the effect of the combined propulsion system parame- ters on the integral dose of radiation accumulated during the maneuver, when putting a spacecraft into a geostationary orbit. Different variations of the combined propulsion system application (thrust variations) allow to optimize the maneuver of the spacecraft and to reduce the integral dose of radiation. As a result of the work, a method was proposed to evaluate the influence of the parameters of the combined propul- sion system taking into account the passage of the Earth radiation belts, the program was implemented, calculations were made and the results were analyzed.

Construction of communication spacecraft with large-size transformable antennas developed tendencies to increase the operational band frequencies, to reduce specific mass and to increase the overall dimensions of the structures. The improvement of technical performance of communication spacecraft with large-size antennas cannot be achieved with- out ensuring the required accuracy of antenna pattern and of the antenna gain coefficient at its maximum. Factors affecting the final quality of large-size structures for space application (of antennas in particular), keep influencing the products through all their service life - from design and production to tests and actual operation. The “direct” elimination of the negative factors affecting the final output is often unprofitable considering the present de- velopment of technological support in hi-tech industries. In this respect, control of the ultimate operational characteris- tics of large-size spacecraft antennas in conditions of real performance, and compensation, if necessary, of deviations from the required values, is optimal with respect to the output/cost ratio. This approach is practical in determining the onboard antenna pattern and compensating its operational distortions in the process of specified spacecraft performance. There are two methods of measuring the antenna pattern at the orbit. The first method is based on measurements of radio engineering characteristics obtained from ground space vehicles’ service stations. This method is sufficiently accurate, but it has several drawbacks. For example, this method increases the number of requirements to ground stations - their number, location and characteristics of the equipment in use. The second method bases on obtaining radio engi- neering characteristics from the configuration and orientation of antenna reflector. The reflector is imaged as a cloud of checkpoints reflecting the deviations of the construction’s configuration and orientation from the specified values. To obtain the antenna pattern measurements using the second method, an antenna configuration control system (ACCS) must be worked out for measuring the coordinates of the reflector surface points. To perform its specific func- tion, the system should have the following configuration: measuring equipment mounted on the spacecraft casing, and control elements fixed on the construction components. This configuration allows to present the antenna construction components in the form of checkpoint cloud. In the process of the system development the constructional analysis of the possibility of using the antenna configu- ration measurements for the its pattern calculation and for further assessment of its deviation from the specified values was made. This article presents the assessment of the required number of monitored checkpoints on the reflector sur- face. For this purpose, Ku-band of frequencies was chosen as one of the most common frequency bands used by telecommunication spacecraft. Several sets of points were considered, among them the sets belonging both to the deformed reflector profile and to the one without deformation. For each set the antenna pattern calculation was made. Visual representations of the focal beam and the directive antenna gain were compared. The analysis of the obtained data allowed to determine the necessary minimum of checkpoints for antenna pattern calculation with the required accuracy. The obtained data were taken into account in formulating the requirements for the system of orbital control of antenna configuration.

The applications of space vehicles in the modern world are extensive enough: satellite communication, broadband and narrowband broadcasting, meteorology, scientific research and others. For this reason, modern space vehicles use the latest achievements of science and technology. It allows us to create easy, compact space vehicles with a wide functional. The devices developed in the Research and Production Center “Polus” should meet the requirements of advanced reliability both for regular and for emergency operating modes. One of the scopes of application of such devices is designing of space vehicles. The main task at designing and manufacturing of devices and their components is reliability maintenance. This is a primary requirement to custom-made products for which repair at major failures is extremely labor-consuming. At the same time, serious demands are made to mass, dimensional characteristics, power consumption, payloads, noise characteristics of separate blocks and devices, and other technical parameters. However, it is necessary to consider that at high requirements to characteristics the process of creation of products should be technological. There are various techniques to define reliability of technical devices and their components. One of such ways is carrying out the whole complex of tests simulating a full cycle of operation of the device or a mechanism. However, experimental techniques have essential disadvantages, namely: high cost and long duration. Mathematical modelling allows us to reduce expenses on mock-up designing, engineering time, risks, to reveal weak points, to develop recom- mendations for strengthening the design and to give preliminary conclusions about firmness of the device to loads. Along with thermal, electrostatic and frequency characteristics, mechanical effects play an important role, i. e. dynamic and static loads. In this paper, the results of modelling of external mechanical effects on the device are pre- sented. Numerical modelling of quasi-static loading and effect on the device of random vibration is conducted and the modal analysis is carried out. Oscillation modes of the first three resonant frequencies of the device, stress, displace- ments and accelerations diagrams are obtained. Load factors, the maximum values of displacements and accelerations at impact actions are determined.

The results of experimental studies combined with modeling and prediction methods for the properties of hard metal composites show that modification with additives of ceramic nanoparticles and composite powders (WC-Co) allows to control microstructure parameters and provides the increase in binding durability and the level of physicomechanical properties of a hard alloy in general. Simultaneous complex application of submicrocrystalline WC carbides coated with Co layer and alloying additives of Al2O3 nanoparticles - grain growth inhibitors of the main phase, can be consid- ered as the most perspective direction of nanostructured hard metal with increased hardness, strength and crack resis- tance production. The coating of carbide particles with a binder layer is an effective starting method that allows to ob- tain a volumetric billet with maintaining the unique properties of the initial nanopowders and ensures a uniform distri- bution of the phases (WC, Co, Al2O3). Such a multiphase fragmented nanostructured composite is characterized by additional heterogeneity, determined by differences in size and elastic phases properties. By combining the sizes and properties of the phase components in such a heterogeneous composite, it is possible to provide an increase in the frac- ture energy, i. e., Palmkvist crack resistance up to 16-18 MPa m1/2 (due to inhibition on nanoparticles inclusions, stress reliefs and changes in intercrystalline crack trajectory, its length decrease). Based on the proposed stereological mod- els and the experimentally established relationships between composition and microstructure parameters, the required volume concentrations of nanoparticles additives and composite powders (WC-Co) were determined.

The modern solar arrays for the most spacecrafts consists of solar cells which are formed by the thirty nano- and micro-dimensional epitaxial layers based on AIIIBV materials forming triple junction InGaP / InGaAs / Ge. This article presents the results of a study of experimental samples of thin single-crystal epitaxial InxGa1-xP layers with different indium and gallium concentrations (x = 38 to 53 %) that were grown on Ge - substrate by MOCVD industrial equip- ment. The theme of present investigation is the influence of epitaxial growth parameters on the crystal structure charac- teristics. The ratio of the components of the third group in the gas phase were calculated from the specified technological parameters. The rocking curves obtained by high-resolution two-crystal X-ray diffractometry were investigated. The lattice parameter and the ratio of indium to gallium in the solid phase were calculated. A high perfection of a single- crystal structure with an insignificant broadening of the X-ray diffraction peaks was observed in the range from 45 to 53 %. It is shown that the broadening of the diffraction peak of the structure can be the criterion of estimation of the quality of the grown structure in addition to the mismatch of diffraction maximum. Also the In / (In + Ga) ratio in the solid phase was calculated using the method of photoluminescence effect measuring. It was shown in comparison of data of x-ray diffraction with photoluminescence method the composition determination by photoluminescence method should be considered only as estimated.

The paper describes materials based on solid solutions GdxMn1-xS and GdxMn1--xSe, which in the future can be used in aerospace industry as sensors, detectors, and information writer-readers. In solid solutions GdxMn1-xA (A = S, Se) (x ≤ 0.2), capacitance and tangent of the dielectric loss angle were meas- ured at the frequency of 10 kHz without a magnetic field and in the magnetic field of 8 kOe in the temperature range 100-500 К. The growth of the dielectric permittivity and the maximum of dielectric losses in the low-temperature region were observed. The displacement of the temperature of the maximum of the imaginary part of the permittivity in the direction of high temperatures is found with increasing concentration. For two compositions, a magnetocapacitance effect was observed. The magnetocapacitance effect δεН = (ε(Н,T)-ε(0,Т))/ε(0,Т)) was determined as a result of inves- tigation of the complex dielectric permittivity. The synthesis of new chalcogenide compounds in the cationic substitution of manganese by gadolinium in the MnS and MnSe systems will make it possible to clarify the effect of the anion system, as a result of studying its magnetoresis- tive properties with concentration in the gadolinium ion flux region along the x ≤ 0.2 lattice. Dielectric losses are described in the Debye model with the freezing of dipole moments and in the model of orbital- charge ordering.

Satellite systems continue to play an important role in developing of telecommunication and broadcasting services market by offering an effective technical solution for the transmission and dissemination of various types of information to mobile and fixed subscriber receivers. This trend is raising demand for the spectrum-orbit resource (SOR) which provides the operation of any radio-electronic system and this leads to a shortage of this valuable resource. The inter- national administrative management system, based on technical and normative principles and procedures set in the Radio Regulations, which successfully coped with its tasks of SOR distribution under conditions when several satellite nations have an insignificant number of satellites in the geostationary orbit, under conditions of current loading, shows its inefficiency. The procedure of obtaining authorization to use the resource involves considerable expenditure of time and material resources raising transaction costs on development of satellite projects and increasing financial risks, which makes investment in satellite projects less attractive. In this regard there is a question of the necessity of stimu- lating rational use of SOR methods introduction. We are considering the possibility of introducing economic methods into the international SOR management system as an additional tool to encourage the rational use of the resource. An analysis of the existing approaches of contempo- rary economic theory has identified some basic options for applying economic methods to the SOR management system. For the planned frequency bands, distributed for satellite services, the introduction of national assignments rent system is offered. For unplanned frequency bands, the introduction of payments for the SOR use is being considered. On the basis of electromagnetic compatibility of satellite communication systems assessment analysis, the methods to deter- mine payments for SOR based on assessments of a satellite system aggressivity in terms of creating interference and of its sensitivity to interference from other systems are offered.