Conceptual scenarios for development of ground infrastructure for receiving mission payload data from a perspective Earth remote sensing satellite constellation

The paper addresses the problem of cooperative development of ground space infrastructure and orbital constellation of Earth remote sensing spacecraft (ERS). In view of the considerable number of elements in space and ground segments of a heterogenous space ERS system, a mechanism is required for developing its concepts involving acquiring updated inputs for determining measures to optimize the ERS ground segment configuration geography-wise and outfit receiving systems for receiving the mission payload data from high-performance ERS spacecraft. The paper describes trends in the development of equipment and technologies for transmitting ERS mission payload data, in particular, the current status of the high data rate optical backbone network in order to determine possible locations for ERS Ground Segment elements. It introduces indicators which provide system-level characterization of the capabilities for a distributed network of data receiving stations. Based on the obtained data, system-level patterns were determined in the development of the ground segment for receiving the ERS mission payload data depending on the state of the ERS orbital constellation, driving further development of growth strategy for the ERS ground space infrastructure. Key words: Earth remote sensing, concept, mission payload data, receiving system, data reception station.

Conceptual design studies of an electrically propelled upper stage for deployment of a multi-plane orbital constellation of small spacecraft

The paper presents results of conceptual design studies to determine configuration of an electrically propelled upper stage (EPUS) – a space transportation stage (a space tug) with main engines based on electric propulsion powered by solar arrays. It addresses the problem of deploying a multi-plane orbital constellation of small spacecraft (SSC) using an electrically propelled upper stage. It proposes to change the SSC operational orbital planes based on the effect of the difference in precession rates between the parking and the working orbits owing to the effect of eccentricity in the Earth gravitational field. Requirements have been defined for the EPUS electrical propulsion system that take into account the need to operate it to offset the aerodynamic drag while waiting in the parking orbit for the SSC operational orbital plane to turn. It demonstrates the feasibility of employing four EPUS that use Stationary Plasma Thruster-type electric propulsion as their main engines and gallium arsenide solar arrays for deployment in a 600 km orbit in four planes an orbital constellation of 24 small spacecraft with a mass of ~250 kg each using one launch of a medium capacity launch vehicle of Soyuz-2.1b type. Key words: Electrically propelled upper stage, electric propulsion, small spacecraft, orbital constellation.

Conceptual design studies of an electrically propelled upper stage for deployment of a multi-plane orbital constellation of small spacecraft

The paper presents results of conceptual design studies to determine configuration of an electrically propelled upper (a space tug) with main engines arrays. It addresses the problem stage (EPUS) — a space transportation stage based on electric propulsion powered by solar of deploying a multi-plane orbital constellation of to in of small spacecraft (SSC) using an electrically propelled upper stage. It proposes change the SSC operational orbital planes based on the effect of precession rates between the parking and the working orbits eccentricity in the Earth gravitational field. Requirements owing have the difference to the effect been defined for the EPUS electrical propulsion system that take into account the need to operate it to offset the aerodynamic drag while waiting in the parking orbit for the SSC operational orbital plane to turn. It demonstrates the feasibility of employing four EPUS that use Stationary Plasma Thruster-type electric propulsion as their main engines and gallium arsenide solar arrays for deployment in a 600 km orbit in four planes an orbital constellation of 24 small spacecraft with a mass of ~250 kg each using one launch of a medium capacity launch vehicle of Soyuz-2.1b type.

SOFTWARE AND MATHEMATICAL SUPPORT FOR THE ANALYSIS OF OPTIONS FOR CONSTRUCTING ORBITAL GROUPINGS OF THE GLONASS SUPPLEMENT

The high accuracy and stability of Global Navigation Satellite System (GLONASS) consumer characteristics allows us to consider it as the basis of coordinate-time and navigation support for regional consumers. At the same time, one of the key factors influencing their choice of the preferred navigation system is to ensure the required levels of accuracy, availability and continuity of the radio navigation field in conditions of complex terrain, urban development and in areas with a high vegetation index. In this sense, the introduction of additional spacecraft into the GLONASS orbital constellation will increase its competitiveness. The article presents a methodology for building software analysis tools options build orbital groups, which allows you to explore the options of structures high-orbit segment of the principles and methods of their construction in order to effectively ensure implementation of navigation services, to analyze the deterioration of the quality of functional capabilities of high-orbit space of the complex due to the deformation under the influence of disturbing factors of various types and build a strategy for correction of motion of spacecraft. The composition and structure of software and mathematical support are proposed. Presents principles of organization and brief description of the software modules comprising: a module to determine the parameters of the perturbed uncontrolled motion of navigation satellites orbital constellation on the interval active life, module to evaluate degradation of functionality for advanced GLONASS and module support decision-making on strategies for correction of navigation satellites by determining the required reserves of the characteristic velocity.

MODERN SPACE RADAR SYSTEMS OF EARTH MONITORING

This article explores brief overview of modern radar systems for imaging and monitoring the Earth from space. The operating radar systems are divided into four classes: large spacecraft with global monitoring SAR, medium-sized spacecraft with detailed observation SAR, small spacecraft with detailed observation SAR, and commercial mini-spacecraft with detailed observation SAR. Listed are the main representatives of each class. Such large satellites as: European – Sentinel-1 (A, B); Japanese – ALOS-2; Canadian company MDA – Radarsat-2; Argentine – SAOCOM-1A / 1B; Chinese – Gaofen-3. Representatives of the class of mid-size spacecraft with SAR: German Aerospace Center (DLR) and the leading European space company Airbus DS – TerraSAR-X, TanDEM-X; Spanish PAZ; the Italian constellation of Cosmo-SkyMed satellites of the first and second generation; Japanese group IGS-Radar; Korean – KOMPSAT-5; Russian satellites “Kondor”. The small class includes Israeli mission satellites – TecSAR, RISAT-2 (India), Ofeq-10; Japanese – ASNARO-2, German satellites SAR-Lupe, English – NovaSAR-1. The last class of mini-spacecraft includes American - Capella and Finnish – ICEYE. The article also presents spacecraft for radar imaging, planned for launch, namely: the second generation of Italian satellites COSMO-SkyMed – CSG-2; 8 ICEYE spacecrafts (Finland); an increase in the Capella constellation, X-band radar satellites of the SuperView constellation and radar satellites Zhuhai (China); ALOS-4 JAXA (Japan); KOMPSAT-6 (Korea), radar satellites of the IRS constellation (India), American satellites XpressSAR, PredaSAR, EOS SAR, satellites of the Russian design Obzor-R1 and KondorFKA, as well as the space complex planned by ROSKOSMOS, including an orbital constellation of 6 small spacecraft for radar surveillance.

Diagnostic method for GLONASS onboard transmitters using monitoring system based on small-size reflector antenna

Regular measurements of the power level of the satellite signals make it possible to detect abnormal functioning of the on-board transmitting device. Due to the high complexity, the large mass of the moving units and the presence of a mechanical drive, it is difficult to carry out regular measurements of the power of the signals of the orbital constellation using large-aperture monitoring systems. To monitor the GLONASS satellites, a small-sized non-power system based on a fixed antenna with a diameter of D = 2 m was developed and put into operation, which allows the NSV self-passage through the main beam of the diagram to make regular assessments of the received power level of the radio navigation signal. The aim of the work is to identify malfunctions of the on-board transmitting devices of the full orbital constellation of the GLONASS satellite based on data obtained by a small-sized monitoring system. The analysis of the data obtained in the period from March 22 to August 11, 2020 revealed 6 NSVs with one or two failed on-board amplifiers and 3 NSVs with three, which was later confirmed by telemetry data. The practical significance of the work lies in the development of a method and a working prototype for alternative diagnostics of the onboard transmitting devices of the GLONASS satellite.

Increasing the Efficiency of the Small Spacecraft Cluster Telemetry Radio Links

The article is devoted to the study of the energy and frequency efficiency of frequency modulated signals with a continuous phase. The values of efficiency indicators obtained from the results of the study made it possible to supplement the existing diagrams of the efficiency of telemetric radio lines with new values. The results of the work simplify the task of selecting signals to ensure information exchange via telemetric radio lines of the cluster under the conditions of restrictions imposed on energy resources. The analysis of efficiency indicators of angular modulation methods used in modern telemetry systems is carried out. The features of the cluster construction of the orbital constellation of small spacecraft are taken into account. The use of frequency modulated signals with a continuous phase is proposed, which makes it possible to increase the energy efficiency of telemetry radio lines due to intersymbol phase connections inherent in this class of signals. Based on the results of the simulation, the values of performance indicators for the proposed signals are determined. Intersymbol phase connections were taken into account using the Viterbi algorithm. The values of the modulation indices of frequency modulated signals with continuous phase, which are of practical interest, are determined. The use of the proposed signals makes it possible to obtain an energy gain of up to 3 dB in comparison with the signals used at present. The values of the modulation indices, the use of which is impractical, are highlighted.

SPACE RADAR SYSTEMS OF EARTH MONITORING

This article explores the relevance of radar sensing methods. The principles of its operation and the advantages of use are considered: the independence of obtaining images from weather conditions and the time of day, the possibility of wide viewing at long ranges with high resolution and the flexibility of controlling and changing radar parameters, which allows you to vary the position and size of the viewing area, resolution and forms of information. In addition, the main satellite radar systems were considered: satellites of the European Space Agency ERS-1,2 and ENVISAT; Canadian satellites of MDA Radarsat-1,2; satellites launched by the German Aerospace Center (DLR) and the leading European space company Airbus DS-TerraSAR-X, TanDEM-X; Spanish satellite PAZ; Japanese satellites ALOS and ALOS-2; Italian constellation of Cosmo-SkyMed satellites; Indian satellite RISAT-1; English satellite NovaSAR-1; Finnish ICEYE satellites; Korean satellite KOMPSAT-5, Chinese satellite Huan Jing 1C, European satellites Sentinel-1 (A, B) and Russian satellites Condor. Also in this article are considered radar spacecraft planned to launch, namely: the second generation of Italian satellites COSMO-SkyMed – CSG – 2; 2 spacecraft ICEYE (Finland); 4 X-band radar satellites SuperView (China); 2 radar satellites Zhuhai (China); ALOS-4 JAXA (Japan); KOMPSAT-6 (Korea), 3 radar spacecraft of the IRS constellation (India), SAOCOM (Argentina), Russian-made satellites Obzor-P1 and Kondor-FKA, in addition, ROSKOSMOS plans to create a space complex that includes an orbital constellation of 6 small-sized spacecraft for radar observation

Methods of validation of the ballistic structure of space surveillance system orbital segment

Space activity brought about the space debris problem that constitutes a threat to active spacecraft. Nowadays the most efficient way of spacecraft protection against space debris is choosing the appropriate orbit parameters to prevent collisions of space objects. To do this one should know the parameters of motion of space objects (SO). At present the task of determining SO orbit parameters is solved be means of the space surveillance system (SSS). The Russian space surveillance system includes only ground based facilities located on the territory of the Russian Federation and Tajikistan. This fact does not allow determining the parameters of SO motion over the Western and Southern Hemispheres. The task of monitoring SO in low orbits (up to 2000 km height) is of particular importance because there have already been collisions that generated a lot of debris which, in their turn, pose a new threat to Russian active spacecraft. To prevent prospective threats to the Russian orbital constellation associated with possible generation of new debris as a result of impacts or spontaneous separation (because of an explosion, for instance) of active SOs the parameters of motion of newly emerging space objects need to be determined quickly and efficiently. We propose to solve the task of online monitoring of space object motion by creating an orbital segment of SSS. The creation of the new system is to be preceded by the development of scientific methods for justification of its ballistic structure. This article presents a method based on the solution of an optimization task, where the target function is the dependence of the required number of measurer spacecraft on the quality indicators of space surveillance.