• Title/Summary/Keyword: Satellite structure

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Constructing Nonlinear Sliding Surface for Spacecraft Attitude Control Problems

  • Cheon, Yee-Jin
    • 제어로봇시스템학회:학술대회논문집
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    • 1999.10a
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    • pp.41-44
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    • 1999
  • Nonlinear sliding surface design in variable structure systems for spacecraft attitude control problems is studied. A robustness analysis is performed for regular form of system, and calculation of actuator bandwidth is presented by reviewing sliding surface dynamics. To achieve non-singular attitude description and minimal parameterization, spacecraft attitude control problems are considered based on modified Rodrigues parameters(MRP). It is shown that the derived controller ensures the sliding motion in pre-determined region irrespective of unmodeled effects and disturbances.

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3D Optimal Layout Design of Satellite Equipment (위성 구성품의 3차원 최적 배치 설계)

  • Yeom, Seung-Yong;Kim, Hong-Rae;Chang, Young-Keun
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.43 no.10
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    • pp.875-887
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    • 2015
  • The optimal layout design is used in the development of various areas of industry. In the field of space systems, components must be placed properly in the limited space of spacecraft by considering mechanical, thermal and electrical interfaces. When applying optimal layout design, a proper, even ideal placement of components is possible in the limited space of a satellite platform. Through the optimal placement design, the minimized moment of inertia enhances efficient attitude control, rapid maneuver and mission performance of the satellite. This paper proposes 3D optimal layout design that minimizes the spacecraft's moment of inertia and effect of thermal dissipation between inner components as well as interference between inner components based on a cubic-structure satellite platform. This study proposes the new genetic algorithm for 3D optimal layout design of the satellite platform.

A Synchronization Tracking Algorithm to Compensate the Drift of Satellite in FH-FDMA Satellite Communication System (FH-FDMA 위성 통신 시스템에서 위성 드리프트 보정 동기추적 알고리즘)

  • Bae, Suk-Neung;Kim, Su-Il;Choi, Young-Kyun;Jin, Byoung-Il
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.2A
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    • pp.159-166
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    • 2008
  • In this paper, we proposed an algorithm to solve the problem that can't maintain hop synchronization using only early-late gate tracking loop due to the drift of geo-stationary satellite in frequency hopping satellite communication system. When the signal is transferred to downlink through DRT(Dehop-Rebop Transponder), the problem with synchronization loss is occurred periodically when using only early-late gate tracking loop, because of energy loss in each side portion of hop due to orbital variation of the satellite. To solve this problem, we have developed Anti-Shrink synchronization tracking algorithm which uses the prediction value of transmission timing and the structure of inner-outer gate instead of early-late gate with the ranging information. Through simulations, we showed that the performance of the Anti-Shrink algorithm is better than that of simple inner-outer energy ratio algorithm and similar to that of conventional early-late tracking loop algorithm with ranging information. No synchronization failure in the proposed algorithm was occurred because of less energy loss and robustness without the ranging information.

Wideband Signal Generator Implementation for Earth Observation Satellite (지구관측위성 광대역 신호 발생기 구현)

  • Kim, Joong-Pyo;Ryu, Sang-Burm;Lim, Won-Gyu;Lee, Sang-Kon
    • Journal of Satellite, Information and Communications
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    • v.8 no.2
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    • pp.88-93
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    • 2013
  • The wideband chirp signal generator to enhance the resolution of synthetic aperture radar of obtaining the earth observation image is needed. This paper deals with designing, manufacturing and testing the wideband digital chirp signal generator having high resolution for LEO earth observation satellite. The wideband digital chirp signal generator is implemented with the memory-map based structure which is mostly applied in the satellite, and consists of the digital module to generate the digital chirp signal and the RF module to perform the quadrature modulation. The I/Q signals stored in the memory of the digital module are D/A converted and delivered to be quadrature modulated with the reference signal of 1275 MHz in the RF module. Furthermore, the test bench and GUI to validate the signal generator function are also developed. It is found that the requirement of 144 MHz bandwidth for the digital chirp signal generator is well met. Finally it is noteworthy that the distortion occurred in the chirp signal generator was compensated by the pre-distortion compensation.

A Study on Building a Scalable Change Detection System Based on QGIS with High-Resolution Satellite Imagery (고해상도 위성영상을 활용한 QGIS 기반 확장 가능한 변화탐지 시스템 구축 방안 연구)

  • Byoung Gil Kim;Chang Jin Ahn;Gayeon Ha
    • Korean Journal of Remote Sensing
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    • v.39 no.6_3
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    • pp.1763-1770
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    • 2023
  • The availability of high-resolution satellite image time series data has led to an increase in change detection research. Various methods are being studied, such as satellite image pixel and object-level change detection algorithms, as well as algorithms that apply deep learning technology. In this paper, we propose a QGIS plugin-based system to enhance the utilization of these useful results and present an actual implementation case. The proposed system is a system for intensive change detection and monitoring of areas of interest, and we propose a convenient system expansion method for algorithms to be developed in the future. Furthermore, it is expected to contribute to the construction of satellite image utilization systems by presenting the basic structure of commercialization of change detection research.

Preliminary Design of Monitoring and Control Subsystem for GNSS Ground Station (위성항법 지상국 감시제어시스템 예비설계)

  • Jeong, Seong-Kyun;Lee, Jae-Eun;Park, Han-Earl;Lee, Sang-Uk;Kim, Jae-Hoon
    • Journal of Astronomy and Space Sciences
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    • v.25 no.2
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    • pp.227-238
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    • 2008
  • GNSS (Global Navigation Satellite System) Ground Station monitors navigation satellite signal, analyzes navigation result, and uploads correction information to satellite. GNSS Ground Station is considered as a main object for constructing GNSS infra-structure and applied in various fields. ETRI (Electronics and Telecommunications Research Institute) is developing Monitoring and Control subsystem, which is subsystem of GNSS Ground Station. Monitoring and Control subsystem acquires GPS and Galileo satellite signal and provides signal monitoring data to GNSS control center. In this paper, the configurations of GNSS Ground Station and Monitoring and Control subsystem are introduced and the preliminary design of Monitoring and Control subsystem is performed. Monitoring and Control subsystem consists of data acquisition module, data formatting and archiving module, data error correction module, navigation solution determination module, independent quality monitoring module, and system operation and maintenance module. The design process uses UML (Unified Modeling Language) method which is a standard for developing software and consists of use-case modeling, domain design, software structure design, and user interface structure design. The preliminary design of Monitoring and Control subsystem enhances operation capability of GNSS Ground Station and is used as basic material for detail design of Monitoring and Control subsystem.

A Power Control-Based MF-TDMA Resource Allocation Scheme for Next Generation Military Satellite Communication Systems (차기 군 위성통신망 체계에서 이기종 단말 운용을 고려한 전력제어 기반 MF-TDMA 자원할당 기법)

  • Woo, Soon;Park, Hyung-Won;Lee, Ho-Sub;Yoo, Youn-Sang;Jung, Byung-Gi
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37C no.11
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    • pp.1138-1147
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    • 2012
  • In this paper, an efficient power control based MF-TDMA resource allocation scheme is proposed for next generation military satellite communication systems. The proposed scheme has the flexibility is used to support heterogeneous terminals with differ in transmission capabilities. The method can be divided into two parts : burst size calculation and burst structure determination. At first, we estimate the link budget taken into account a dynamic satellite link state variation. Then, applicable ACM level and burst size is chosen. In burst structure determination phase, we reorganize the burst structure in time-frequency domain by controlling limited power, bandwidth, time resources. In particular, we compensate the power spectral density among different terminals to integrate them in same transponder, Furthermore, we increase the packing efficiency by controlling the ACM level of the burst in applicable power spectral density range. Simulation results show that the method increase the spectral efficiency and burst packing efficiency. In addition, slot allocation rejection ratio is successfully reduced.

Interactive Navigational Structures

  • Czaplewski, Krzysztof;Wisniewski, Zbigniew
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.1
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    • pp.495-500
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    • 2006
  • Satellite systems for objects positioning appeared indispensable for performing basic tasks of maritime navigation. Navigation, understood as safe and effective conducting a vehicle from one point to another, within a specific physical-geographical environment. [Kopacz, $Urba{\acute{n}}ski$, 1998]. However, the systems have not solved the problem of accessibility to reliable and highly accurate information about a position of an object, especially if surveyed toward on-shore navigational signs or in sea depth. And it's of considerable significance for many navigational tasks, carried out within the frameworks of special works performance and submarine navigation. In addition, positioning precisely the objects other than vessels, while executing hydrographical works, is not always possible with a use of any satellite system. Difficulties with GPS application show up also while positioning such off-lying dangers as wrecks, underwater and aquatic rocks also other naturaland artificial obstacles. It is caused by impossibility of surveyors approaching directly any such object while its positioning. Moreover, determination of vessels positions mutually (mutual geometrical relations) by teams carrying out one common tasks at sea, demands applying the navigational techniques other than the satellite ones. Vessels'staying precisely on specified positions is of special importance in, among the others, the cases as follows: - surveying vessels while carrying out bathymetric works, wire dragging; - special tasks watercraft in course of carrying out scientific research, sea bottom exploration etc. The problems are essential for maritime economy and the Country defence readiness. Resolving them requires applying not only the satellite navigation methods, but also the terrestrial ones. The condition for implementation of the geo-navigation methods is at present the methods development both: in aspects of their techniques and technologies as well as survey data evaluation. Now, the classical geo-navigation comprises procedures, which meet out-of-date accuracy standards. To enable meeting the present-day requirements, the methods should refer to well-recognised and still developed methods of contemporary geodesy. Moreover, in a time of computerization and automation of calculating, it is feasible to create also such software, which could be applied in the integrated navigational systems, allowing carrying out navigation, provided with combinatory systems as well as with the new positioning methods. Whereas, as regards data evaluation, there should be applied the most advanced achievements in that subject; first of all the newest, although theoretically well-recognised estimation methods, including estimation [Hampel et al. 1986; $Wi{\acute{s}}niewski$ 2005; Yang 1997; Yang et al. 1999]. Such approach to the problem consisting in positioning a vehicle in motion and solid objects under observation enables an opportunity of creating dynamic and interactive navigational structures. The main subject of the theoretical suggested in this paper is the Interactive Navigational Structure. In this paper, the Structure will stand for the existing navigational signs systems, any observed solid objects and also vehicles, carrying out navigation (submarines inclusive), which, owing to mutual dependencies, (geometrical and physical) allow to determine coordinates of this new Structure's elements and to correct the already known coordinates of other elements.

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디지털 방송 수신기 기술

  • 장현식;김용석;정주홍
    • The Magazine of the IEIE
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    • v.29 no.7
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    • pp.51-58
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    • 2002
  • This paper describes functions required for implementation of digital television (DTV) broadcast receivers. The necessary functions for the DTV receiver vary with the transmission media-terrdstrial, cable and satellite. This paper briefly introduces its hardware and software structure, This paper also presents the future of DTV receivers according to the tomorrow's broadcast environment.

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