• 제목/요약/키워드: low earth orbit (LEO)

검색결과 161건 처리시간 0.025초

Dynamic Caching Routing Strategy for LEO Satellite Nodes Based on Gradient Boosting Regression Tree

  • Yang Yang;Shengbo Hu;Guiju Lu
    • Journal of Information Processing Systems
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    • 제20권1호
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    • pp.131-147
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    • 2024
  • A routing strategy based on traffic prediction and dynamic cache allocation for satellite nodes is proposed to address the issues of high propagation delay and overall delay of inter-satellite and satellite-to-ground links in low Earth orbit (LEO) satellite systems. The spatial and temporal correlations of satellite network traffic were analyzed, and the relevant traffic through the target satellite was extracted as raw input for traffic prediction. An improved gradient boosting regression tree algorithm was used for traffic prediction. Based on the traffic prediction results, a dynamic cache allocation routing strategy is proposed. The satellite nodes periodically monitor the traffic load on inter-satellite links (ISLs) and dynamically allocate cache resources for each ISL with neighboring nodes. Simulation results demonstrate that the proposed routing strategy effectively reduces packet loss rate and average end-to-end delay and improves the distribution of services across the entire network.

추력기를 이용한 저궤도 위성 모멘텀 덤핑 (Low Earth Orbit Satellite Momentum Dumping Using Thruster)

  • 손준원
    • 한국항공우주학회지
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    • 제48권2호
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    • pp.147-158
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    • 2020
  • 본 논문에서는 저궤도 위성에서 추력기를 이용하여 반작용휠 모멘텀을 덤핑하는 방법에 대해서 살펴본다. 추력기를 사용한 모멘텀 덤핑은 주로 정지궤도위성에서 사용되는데 특정 시간에만 추력기로 자세제어와 모멘텀 덤핑을 동시에 수행하는 방식으로 이뤄진다. 저궤도 위성은 수시로 모멘텀 덤핑을 해야 하므로 정지궤도위성의 방식을 사용하는 것은 바람직하지 않다. 본 연구에서는 저궤도 위성에 적용 가능하도록 항상 추력기로 모멘텀 덤핑을 수행하고 덤핑 시의 자세제어는 반작용휠로 수행하는 방법을 살펴본다. 추력기의 밸브 개폐횟수를 줄이기 위해서 최대 크기의 펄스로 추력기를 구동하는 방법을 제안한다. 추력기로 인해 자세오차가 크게 증가하는 것을 방지하기 위해서 추력기의 구동 간격을 조정하였다. 시뮬레이션을 통해서 본 논문에서 제안한 방법의 효과를 검증하였다.

Angles-Only Initial Orbit Determination of Low Earth Orbit (LEO) Satellites Using Real Observational Data

  • Hwang, Hyewon;Park, Sang-Young;Lee, Eunji
    • Journal of Astronomy and Space Sciences
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    • 제36권3호
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    • pp.187-197
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    • 2019
  • The Optical Wide-field patroL-Network (OWL-Net) is a Korean optical space surveillance system used to track and monitor objects in space. In this study, the characteristics of four Initial Orbit Determination (IOD) methods were analyzed using artificial observational data from Low Earth Orbit satellites, and an appropriate IOD method was selected for use as the initial value of Precise Orbit Determination using OWL-Net data. Various simulations were performed according to the properties of observational data, such as noise level and observational time interval, to confirm the characteristics of the IOD methods. The IOD results produced via the OWL-Net observational data were then compared with Two Line Elements data to verify the accuracy of each IOD method. This paper, thus, suggests the best method for IOD, according to the properties of angles-only data, for use even when the ephemeris of a satellite is unknown.

현실적 모델링 갖는 LEO Constellation에서 위성간링크의 성능분석 (Performance Analysis for an Inter-Satellite Link in the LEO Constellation with the realistic modelling)

  • 김영준
    • 대한전자공학회:학술대회논문집
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    • 대한전자공학회 1999년도 하계종합학술대회 논문집
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    • pp.833-836
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    • 1999
  • In this paper, the communication performance and its characteristics of the polar Low Earth Orbit(LEO) mobile satellite have been described in terms of the generalized performance parameters via geometric modeling and analysis. Especially, the general formula related to the parameters such as the number of orbits(M) and the number of satellites per orbit(N) were derived in the LEO satellite system for voice service, and then we applied the general result to IRIDIUM system(M=6, N=11) that would be scheduled to commercialize soon. The offered traffic of Inter Satellite Link(ISL), ISL link blocking probability as well as both new call blocking probability and the probability of forced termination for the on going call are calculated as the result of performance analysis.

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저궤도 위성통신망 기반 글로벌 무선통신 기술 동향 (Research Trends in Global Wireless Communication Technology Based on the LEO Satellite Communication Network)

  • 김판수;유준규;변우진
    • 전자통신동향분석
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    • 제35권5호
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    • pp.83-91
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    • 2020
  • In this paper, the contemporary deployment of broadband and Internet-of-Things (IoT) services based on the Low Earth Orbit (LEO) satellite communication network is presented. First, the global service and key technologies of small and nanosatellites are briefly addressed, and then, the progress of relevant standard technologies is explained. Finally, the overall potential for the future development of the LEO satellite communication network is highlighted.

Channel Allocation for the Low Earth Orbit Satellite Systems

  • Kim, Soo-Hyun;Kim, Soo-Hyun;Chang, Kun-Nyeong
    • 한국경영과학회지
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    • 제22권4호
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    • pp.37-50
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    • 1997
  • We consider the channel allocation problem for the earth orbit (LEO) satellite systems. This problm is known to be NP-complete and a couple of heuristic algorithms have been developed. In this paper, we convert the problem into a simpler form through the concept of pattern. And we suggest another algorithm based on Simulated Annealing for this simplified problem. The results of performance comparison show that our method works very well. Simulation results are reported.

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Operation of the Radio Occultation Mission in KOMPSAT-5

  • Choi, Man-Soo;Lee, Woo-Kyoung;Cho, Sung-Ki;Park, Jong-Uk
    • Journal of Astronomy and Space Sciences
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    • 제27권4호
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    • pp.345-352
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    • 2010
  • Korea multi-purpose satellite-5 (KOMPSAT-5) is a low earth orbit (LEO) satellite scheduled to be launched in 2010. To satisfy the precision orbit determination (POD) requirement for a high resolution synthetic aperture radar image of KOMPSAT-5, KOMPSAT-5 has atmosphere occultation POD (AOPOD) system which consists of a space-borne dual frequency global positioning system (GPS) receiver and a laser retro reflector array. A space-borne dual frequency GPS receiver on a LEO satellite provides position data for the POD and radio occultation data for scientific applications. This paper describes an overview of AOPOD system and operation concepts of the radio occultation mission in KOMPSAT-5. We showed AOPOD system satisfies the requirements of KOMPSAT-5 in performance and stability.

Limitations of Electromagnetic Ion Cyclotron Wave Observations in Low Earth Orbit

  • Hwang, Junga;Kim, Hyangpyo;Park, Jaeheung;Lee, Jaejin
    • Journal of Astronomy and Space Sciences
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    • 제35권1호
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    • pp.31-37
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    • 2018
  • Pc1 pulsations are geomagnetic fluctuations in the frequency range of 0.2 to 5 Hz. There have been several observations of Pc1 pulsations in low earth orbit by MAGSAT, DE-2, Viking, Freja, CHAMP, and SWARM satellites. However, there has been a clear limitation in resolving the spatial and temporal variations of the pulsation by using a single-point observation by a single satellite. To overcome such limitations of previous observations, a new space mission was recently initiated, using the concept of multi-satellites, named the Small scale magNetospheric and Ionospheric Plasma Experiments (SNIPE). The SNIPE mission consists of four nanosatellites (~10 kg), which will be launched into a polar orbit at an altitude of 600 km (TBD) in 2020. Four satellites will be deployed in orbit, and the distances between each satellite will be controlled from 10 to 1,000 km by a high-end formation-flying algorithm. One of the possible science targets of the SNIPE mission is observing electromagnetic ion cyclotron (EMIC) waves. In this paper, we report on examples of observations, showing the limitations of previous EMIC observations in low earth orbit, and suggest possibilities to overcome those limitations through a new mission.

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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    • 제16권3호
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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.

Study on The Attitude Stabilization Techniques of Leo Satellites

  • Hwan, Lho-Young;Yong, Jung-Kang
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2001년도 ICCAS
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    • pp.56.5-56
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    • 2001
  • In the three axis control of satellite by using reaction wheel and gyro, a reaction wheel produces the control torque by the wheel speed or momentum, and a gyro carries out measuring of the attitude angle and the attitude angular velocity In this study, dynamic modelling of the Low Earth Orbit (LEO) is consisted of the one from the rotational motion of the satellite with the basic rigid body and a flexible body model, and the gyro in addition to the reaction wheel model. The results obtained by the robust controller are compared with those of the PI (Proportional and Integration) controller which is commonly used for the stabilizing satellite.

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