I. INTRODUCTIONGlobal navigation satellite systems (GNSS) -one of the simplest and cheapest methods of navigation in modern society. This is not surprising -the users only have to purchase a receiver, since the main system is free and publicly available (the constellation owners pay cost of maintaining the system). Over the years of its work, satellite navigation has been used in different spheres of society, including transport, agriculture, tourism, navigation, etc. Despite the fact that the system was originally designed to be used on the surface of the Earth or near the lower Earth orbits that is called Terrestrial service volume (TSV), GNSS can be used for navigation in the near-Earth space that was named space service volume (SSV).
While facing different tasks in space, the necessity to create a reliable way of navigation for different manned on unmanned vehicles in space is required. The model in this work was created in MATLAB software package to analyze the availability of the navigation satellites in space, coordinates estimation and allows simulating different parameters. A way to navigate in space for a space vehicle is required for multiple purposes, like so-called "orbital service" or space debris extraction. Satellite navigation seems to be a cheap system for navigation in space, thus allowing to use existing system framework with only adding an extremely sensitive receiver.
In this paper we consider the possibilities of navigation of spacecrafts designed to service artificial Earth satellites on the geostationary orbit and of space debris removal in the near-Earth space using the signals of Global Navigation Satellite Systems. We have formulated the methodology for estimation of the signals availability of navigation satellites on the geostationary orbit through the utilization of almanac of GPS and GLONASS. It has been demonstrated that in the case of reception of navigation signals, which are radiated by the antenna system within the limits of main lobe of the radiation pattern (RP), the availability of satellite navigation signals on the geostationary orbit is very low even if we utilize GPS and GLONASS simultaneously. We present the simulation results of the received on the geostationary orbit navigation satellites using the signals radiated in the main lobes in the range from ±13.8 to ±23.5°for the L1 frequency, from ±13.8 to ±26°for the L2/L5 frequencies and in the side lobes in the range from ±30 to ±60°of RP of the satellite antennas. The simulation of the navigation satellites available on the geostationary orbit is given on the 24-hour time interval. Presented results are illustrated by the calculations of number of visible satellites and by the geometric factor.
Представлені результати досліджень роботи системи EGNOS в Україні. Проаналізовані точність, неперервність, доступність, цілісність цієї системи і на їх основі зроблені висновки про необхідність створення наземного доповнення для EGNOS в Україні.
Satellite systems are a fast-developing and broad field of study. The use of global navigation satellite systems for relatively autonomous spacecraft navigation holds a lot of interest for researchers. It is extremely expensive to research space applications as live experiments. Therefore, computer modelling comes in handy when there is a need to analyze important factors in space environment. The chapter describes the radionavigation field model that uses the off-nadir satellites. This model allows estimation of the availability and accuracy characteristics of autonomous satellite navigation in space up to the geostationary orbit in order to provide the necessary research data.
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