• The Plant Pathology Journal
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• 제22권2호
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• pp.131-138
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• 2006

Two strains of Cucumber mosaic virus (CMV) isolated in Kuwait were confirmed their infectivity based on symptomatology and host range on different cultivars of tomato (Lycopersicon esculentum), tobacco(Nicotiana tabacum L.) and squash (Cucurbita pepo). The pattern of symptoms differed for the two CMV strains in tomato and tobacco, showing severe stunting and mosaic symptoms with one strain designated KU2, and almost symptomless with the other strain designated KU1. A satellite RNA 5 (sat-RNA) was found to be associated with the KU1 strain and was characterized as a benign viral satellite RNA. Using reverse transcription and polymerase chain reaction (RT-PCR) with sat-RNA specific primers, an amplified PCR product of about 160bp was determined and analyzed by gel electrophoresis. This naturally occurring benign viral satellite RNA was successfully used as a biological control agent to protect tomato plants against the severe KU2 strain. Tomato plants grown in plant-growth chambers, were preinoculated with KU1 containing the benign viral satellite and then challenge inoculated with the severe KU2 strain at different time intervals. All plants challenged three weeks after preinoculation showed nearly complete protection from subsequent infection by the severe strain. This biological control technology using plant viruses was found protective and could be successfully established sooner after the preinoculation.

• 한국위성정보통신학회논문지
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• 제5권2호
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• pp.29-33
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• 2010

위성 산업은 상업적 군사적 유용성 등의 특성으로 인해 지속적인 발달이 이루어져 왔다. 이중에서도 위성의 전력 시스템은 위성의 수명에 직접적인 관련을 가지고 있으며, 실제 궤도상에서의 Test가 불가능한 특성을 보인다. 또한 저궤도 소형위성은 전력에 민감하므로, 효과적인 전력의 안정화 및 신뢰성 향상은 중요한 문제이다. 일반적으로 저궤도 위성의 전력은 각 부하의 특성에 따라 변환 및 제어가 이루어진다. 따라서 저궤도위성의 전력 시스템은 일반적으로 여러 단계의 전력 변환을 거치게 되므로, 신뢰성 향상을 위한 1차 및 2차 혹은 그 이상 단계의 Converter의 일반화 모델링 및 안정화를 위한 제어기 설계 및 외란에 의한 영향성의 분석이 요구된다. 본 논문에서는 저 궤도 위성 전력계 시스템의 전력 변환을 위한 Converter의 일반화 모델링을 통해 안정화 설계를 위한 파라미터를 추정하고 이를 통한 신뢰성 향상 및 최적 제어 방법에 대해 알아보기로 한다.

• 전자공학회논문지SC
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• 제46권6호
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• pp.9-13
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• 2009

반작용과 자이로를 사용하는 저궤도 위성체의 3축 제어에서 반작용휠은 휠 속도나 운동량으로 제어토크를 만들고 자이로는 자세각과 자세각속도를 측정한다. 본 논문에서 저궤도 위성체의 다이나믹 모델링은 기본적인 본체만을 고려한 강체에 태양전지판 등을 고려한 연성체의 회전운동방정식과 반작용휠로 구성된다. 강인제어기$(H_\infty)$는 외란에 의한 모델이 가변될 수 있는 강체 및 연성체를 포함한 플랜트를 안정화시키기 위해 적용하였으며, 기존 저궤도 위성체를 안정화시키기 위해 사용된 PI 제어기와 성능을 비교하여 자세제어에 필요한 위상제어의 우수성을 보여주는데 있다.

• 항공우주기술
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• 제10권2호
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• pp.87-93
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• 2011

고정밀 태양센서는 인공위성의 자세제어에 중요 센서로서, 위성으로 입사되는 태양 빛의 방향을 측정하거나 위성이 태양을 보지 못하는 상태에 있는지를 판단하기 위해서 사용되고 있다. 또한 정지궤도 위성에서는 전이궤도 및 임무궤도 상에서 기준 자세로 부터 벗어난 자세오차 정보를 획득하기 위해서 또는 이상 발생 시 태양벡터를 획득하기 위해서 고정밀 태양센서를 사용하고 있다. 본 논문에서는 저궤도 위성과 정지궤도 위성용 고정밀 태양센서의 형상에 대한 이해를 바탕으로 태양의 입사각에 대한 출력 전류 관계를 나타내는 전달 함수를 이용하여 고정밀 태양센서 운용 원리를 설명한다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.225-227
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• 2003

Traditional photogrammetry and satellite image rectification technique have been developed based on control-points for many decades. These techniques are driven from linked points in image space and the corresponding points in the object space in rigorous colinearity or coplanarity conditions. Recently, digital imagery facilitates the opportunity to use features as well as points for images rectification. These implementations were mainly based on rigorous models that incorporated geometric constraints into the bundle adjustment and could not be applied to the new high-resolution satellite imagery (HRSI) due to the absence of sensor calibration and satellite orbit information. This research is an attempt to establish a new Line Based Transformation Model (LBTM), which is based on linear features only or linear features with a number of ground control points instead of the traditional models that only use Ground Control Points (GCPs) for satellite imagery rectification. The new model does not require any further information about the sensor model or satellite ephemeris data. Synthetic as well as real data have been demonestrated to check the validity and fidelity of the new approach and the results showed that the LBTM can be used efficiently for rectifying HRSI.

• International Journal of Computer Science & Network Security
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• 제22권3호
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• pp.382-388
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• 2022

Satellite communication for high altitude platform stations (HAPS) and low earth orbit (LEO) systems suffer from dust and sand (DU&SA) storms in the desert regions such as Saudi Arabia. These attenuations have a distorting effect on signal fidelity at high frequency of operations. This results signal to noise ratio (SNR) to dramatically decreasing and leads to wireless transmission error. The main focus in this paper is to propose common relations between HAPS and LEO for the atmospheric impairments affecting the satellite communication networks operating above Ku-band crossing the propagation path. A double phase three dimensional relationship for HAPS and LEO systems is then presented. The comparison model present the analysis of atmospheric attenuation with specific focus on sand and dust based on particular size, visibility, adding gaseous effects for different frequency, and propagation angle to provide system operations with a predicted vision of satellite parameters' values. Skillful decision and control system (SD&CS) is proposed to control applied parameters that lead to improve satellite network performance and to get the ultimate receiving wireless signal under bad weather condition.

• Journal of Astronomy and Space Sciences
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• 제28권4호
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• pp.273-284
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• 2011

A method of stellar source selection for validating the quality of image is investigated for a low Earth orbit optical remote sensing satellite. Image performance of the optical payload needs to be validated after its launch into orbit. The stellar sources are ideal source points that can be used to validate the quality of optical images. For the image validation, stellar sources should be the brightest as possible in the charge-coupled device dynamic range. The time delayed and integration technique, which is used to observe the ground, is also performed to observe the selected stars. The relations between the incident radiance at aperture and V magnitude of a star are established using Gunn & Stryker's star catalogue of spectrum. Applying this result, an appropriate image performance index is determined, and suitable stars and areas of the sky scene are selected for the optical payload on a remote sensing satellite to observe. The result of this research can be utilized to validate the quality of optical payload of a satellite in orbit.

• 한국위성정보통신학회논문지
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• 제5권1호
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• pp.48-53
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• 2010

2010년 6월 23일 발사되어 동경 128.2도의 정지궤도에서 운용하게 될 천리안위성은 Ka대역 통신실험, 해양탐사 및 기상관측 등을 임무로 하는 복합위성이다. 천리안위성의 세 가지 임무중 Ka대역 통신실험을 목적으로 하는 Ka대역 통신탑재체를 효과적이고 원활하게 운용하기 위해서 통신탑재체 감시/제어관리를 목적으로 하는 Ka 대역 통신탑재체 제어관리 시스템(Transponder Monitoring and Control; TMC)이 요구된다. 본 논문에서는 TMC 시스템의 개념과 설계에 대하여 논하도록 한다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1995년도 Proceedings of the Korea Automation Control Conference, 10th (KACC); Seoul, Korea; 23-25 Oct. 1995
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• pp.444-447
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• 1995

The satellite in a circular orbit about a planet with disturbances and a three-degree-of-freedom (3DOF) structure under seismic excitations are modeled by the linear stochastic differential equations. Then the risk-sensitive optimal control method is applied to those equations. The mean and the variance of the cost function varies with respect to the risk-sensitivity parameter, .gamma.$_{RS}$ . For a particular risk-sensitivity parameter value, risk-sensitive control reduces to LQG control. Furthermore, the derivation of the mean square value of the state and control action are given for a finite-horizon full-state-feedback risk-sensitive control system. The risk-sensitive controller outperforms a classical LQG controller in the mean square sense of the state and the control action.

• Journal of Positioning, Navigation, and Timing
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• 제12권2호
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• pp.185-200
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• 2023

The Korea Augmentation Satellite System (KASS) is the first satellite navigation enhancement system in Korea developed in compliance with international standards. Technologies accumulated during the development process should be spread to industries such as academia and serve as the basis for developing the domestic satellite navigation field. This paper introduces the development process from design to implementation, testing, and verification of KASS control systems (KCS). First, development standards, milestones, requirements, and interface standards are presented as KCS development methods, and major functional design, physical design, and hardware/software implementation are described based on the allocated requirements. Subsequently, the verification environment, procedures, and results of the development product are covered and the developed operational and maintenance procedures are described. In addition, based on the experience gained through the development, suggestions were made for beneficial technology development and organization when promoting satellite navigation projects in the future. Since this work has important historical value for the development of domestic satellite navigation, it is expected that the development results will be shared with academia and industry in the future and be used as basic data for similar development.