• Title/Summary/Keyword: LEO satellite

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Determination of the Ground Station Locations for both Dual-Site Ranging and Site-Diversity at Q/V-band Satellite Communication for an Intersatellite System Scenario

  • Yilmaz, Umit C.;Cavdar, Ismail H.
    • International Journal of Aeronautical and Space Sciences
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    • v.16 no.3
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    • pp.445-450
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    • 2015
  • Generally, Low Earth Orbit (LEO) satellites are used to collect image or video from earth's surface. The collected data are stored on-board and/or transmitted to the main ground station directly or via polar ground station using terrestrial line. Today, an intersatellite link between a LEO and a GEO satellite allows transmission of the collected data to the main ground station through the GEO satellite. In this study, an approach for a continuous communication starting from LEO through GEO to ground station is proposed by determining the optimum ground station locations. In doing so, diverse ground stations help to determine the GEO orbit as well. Cross-correlation of the long term daily rainfall averages are multiplied with the logarithmic correlation of the sites to calculate the joint correlation of the diverse ground station locations. The minimum values of this joint correlation yield the optimum locations of the ground stations for Q/V-band communication and satellite control operations. Results for several case studies are listed.

Performance Analysis of Low Earth Orbit Satellite Communication Systems Under Multi-path Fading Environments (다중경로 페이딩 환경하에서의 저궤도 위성통신시스템 성능 분석)

  • Hae-uk Lee;Young-bin Ryu;Hyuk-jun Oh
    • Journal of Advanced Navigation Technology
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    • v.27 no.4
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    • pp.410-416
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    • 2023
  • Unlike geostationary satellite communication systems, low-earth orbit(LEO) satellite communication systems move at relatively high speeds, and the angle with the ground device is not fixed and varies over a wide range. The propagation channel condition between satellites and ground nodes cannot be assumed line of sight(LOS) anymore. This paper analyzes the low-orbit multi-path fading satellite channel model that can occur in LEO satellite communication systems and Doppler frequency transition caused by high-speed maneuvering of LEO satellites and presents effective equalization techniques for OFDM and SC-FDE transmission methods suitable for multi-path frequency selective fading satellite channel models. In addition, this paper compares and analyzes the performance of OFDM and SC-FDE transmission methods in multipath fading LEO satellite channel environment using the proposed equalization techniques through simulations. Simulation results showed that SC-FDE outpeformed OFDM.

Development of Monopropellant Propulsion System for Low Earth Orbit Observation Satellite

  • Lee, Kyun-Ho;Yu, Myoung-Jong;Choi, Joon-Min
    • International Journal of Aeronautical and Space Sciences
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    • v.6 no.1
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    • pp.61-70
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    • 2005
  • The currently developed propulsion system(PS) is composed of propellant tank, valves, thrusters, interconnecting line assembly and thermal hardwares to prevent propellant freezing in the space environment. Comprehensive engineering analyses in the structure, thermal, flow and plume fields are performed to evaluate main design parameters and to verify their suitabilities concurrently at the design phase. The integrated PS has undergone a series of acceptance tests to verify workmanship, performance, and functionality prior to spacecraft level integration. After all the processes of assembly, integration and test are completed, the PS is integrated with the satellite bus system successfully. At present, the severe environmental tests have been carried out to evaluate functionality performances of satellite bus system. This paper summarizes an overall development process of monopropellant propulsion system for the attitude and orbit control of LEO(Low Earth Orbit) observation satellite from the design engineering up to the integration and test.

THE ORBIT DETERMINATION OF LEO SATELLITES USING EXTENDED KALMAN FILTER (확장 칼만 필터를 이용한 LEO 위성의 궤도결정 방법)

  • 손건호;김광렬;최규홍
    • Journal of Astronomy and Space Sciences
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    • v.12 no.1
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    • pp.133-142
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    • 1995
  • We studied the nonlinear estimation problem of extended Kalman filter and appled this method to LEO satellite system. Through this method the performance of extended Kalman filter was analyzed. There were certain presumption taken; J2 and atmospheric drag were simply considered in the dynamic model of LEO satellite and the system noise error of $\sigma_r$=150m, $\sigma_r$=10m/s was presumed in the observation data. As results of this simulation, the overall state estimation errors of extended Kalman filter were within the presumed error range and also the ability of performance was maximized when the condition was the state process noise Q has the 1/10 level of covariance matrix Po.

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Collision Avoidance Maneuver Planning Using GA for LEO and GEO Satellite Maintained in Keeping Area

  • Lee, Sang-Cherl;Kim, Hae-Dong;Suk, Jinyoung
    • International Journal of Aeronautical and Space Sciences
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    • v.13 no.4
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    • pp.474-483
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    • 2012
  • In this paper, a collision avoidance maneuver was sought for low Earth orbit (LEO) and geostationary Earth orbit (GEO) satellites maintained in a keeping area. A genetic algorithm was used to obtain both the maneuver start time and the delta-V to reduce the probability of collision with uncontrolled space objects or debris. Numerical simulations demonstrated the feasibility of the proposed algorithm for both LEO satellites and GEO satellites.

Development of Propulsion System for LEO Satellite (저궤도 위성용 추진계 개발)

  • Yu Myoung-Jong;Lee Kyun-Ho;Han Cho-Young
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2004.10a
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    • pp.83-86
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    • 2004
  • Likewise all that of the propulsion system, development of Propulsion System for LEO Satellite is laborous tasks to surmount technical barriers of the advanced countries as well as to satisfy the requirements of evolving satellites and changes of functions, structures and etc. Those will be presented and discussed here that the process of technical approach to have developed the KOMPSAT propulsion system, and some challenging area to overcome to develop future LEO satellite propulsion system.

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The OBC Reconfiguration Test on LEO Satellite (저궤도 위성에서 위성탑재컴퓨터의 재구성 시험)

  • Jeong, Jae-Yeop;Lee, Cheol-Hoon
    • Journal of Satellite, Information and Communications
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    • v.12 no.3
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    • pp.103-107
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    • 2017
  • The Satellite OBC(On Board Computer) manages critical functionality such as satellite attitude control, fault management, payload management, command/telemetry processing etc. The OBC consist of various modules. Each module perform mission critical operation. So all modules designed as hot or cold redundancy architecture. The redundancy design gives a guarantee high reliability and it allows normal operation of satellite using reconfiguration capability. In this paper, introduces reconfiguration unit operation and describe the results of testing in the ETB.

Performance of CDMA system in the Extended Suzuki Model of LEO Satellite (저궤도 위성의 Extended Suzuki 모델에서 CDMA 시스팀의 성능)

  • 박성조
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.10A
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    • pp.1521-1528
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    • 2000
  • In this paper we analyze the performance of a DS/CDMA system in LEO mobile satellite channels. The channel uses the Extended Suzuki model which is the product of a Rician distribution having a LOS component and a lognormal distribution due to shadowing. We assume that the signal transmitted from the satellite to the mobile undergoes the same fading for the whole coverage of signal's beam. The average bit error probabilities of double coverage system is calculated in this paper. The interference resulting from the reference satellite is calculated for mobile located in the middle of the double coverage region whereas the additive interference from next-satellite is included for mobile located in the edge of the double coverage region. The performance of the mobile's receiving signal is dependent on shadowing and the interference of the next-satellite. We can obtain an obtain an improved average bit error probability by using dual diversity over the conventional correlated receiver for similar shadowing conditions in the coverage area of the satellite channel.

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Bus Voltage Drop Analysis Caused by Payload Operation of LEO Satellite (저궤도 인공위성 탑재체 구동에 따른 버스 전압 강하 해석)

  • Park, Hee-Sung;Jang, Jin-Baek;Park, Sung-Woo;Lee, Sang-Kon
    • Aerospace Engineering and Technology
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    • v.9 no.2
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    • pp.57-62
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    • 2010
  • SAR payload of LEO satellite will consume about 150A current. This high current makes the voltage drop between battery, satellite main bus and payload interface, which cannot guarantee the input voltage level of the satellite electrical unit and payload. So, it is necessary to predict the main bus and payload input voltage level when the payload works. In this paper, the worst case analysis of the harness and contact resistance was executed and predicted the voltage drop when the payload works.

Improvement of Success Rate on LEO Satellite Attitude Determination Using GPS Carrier Phase Measurements (GPS를 이용한 저궤도 위성 자세 결정의 미지정수 결정 성공확률 향상)

  • Lee, Eun-Sung;Chun, Se-Bum;Lee, Young-Jea;Kang, Tea-Sam;Jee, Gyu-In;Jun, Hyang-Sig;Joo, Jung-Min
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.33 no.6
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    • pp.45-50
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    • 2005
  • To determine precise position GPS carrier phase measurements are used. In addition, the multi-antenna system consisting of 2 or more GPS antennas can make attitude determination effectively. When GPS carrier phase measurements are used the integer ambiguity must be fixed. The success rate is used to validate the integer ambiguity. For LEO satellite attitude determination the double difference carrier phase measurements are used, the success rate is calculated using the covariance matrix and the measurement matrix. The constraint that LEO satellite position vector and attitude vector is orthogonal is suggested for improving the success rate. The LEO satellite orbit model is KITSAT3. The results of the simulation are shown and analyzed.