• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.6
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• pp.983-988
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• 2017

This study describes the design and implementation of OMUX(Output Multiplexer) for Satellite Communication. The OMUX unit for SHF band consists of LPF(Low Pass Filter), manifolder and Channel Filter. Through the pre-simulation analysis of space environment, the possibility of the malfunction of equipment minimized and we designed a reliable OMUX through simulation for vibration analysis generated during the launch, and compared pre-simulation of main performance results to test results about main performances of OMUX after production.

• Korean Journal of Remote Sensing
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• v.15 no.3
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• pp.227-238
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• 1999

In advance of launch, simulated radiances of the Ocean Scanning Multispectral Imager (OSMI) will be very useful to guess the real imagery of OSMI and to prepare for data processing of OSMI. The data processing system for OSMI which is one of sensors aboard Korea Multi-Purpose Satellite (KOMPSAT) scheduled for launch in 1999 is developed based on the SeaWiFS Data Analysis System (SeaDAS). Simulation of radiances requires information on the spectral band, orbital and scanning characteristics of the OSMI and KOMPSAT spacecraft. This paper also describes a method to create simulated radiances of the OSMI over the oceans. Our method for constructing a simulated OSMI imagery is to propagate a KOMPSAT orbit over a field of Coastal Zone Color Scanner (CZCS) pigment concentrations and to use the values and atmospheric components for calculation of total radiances. A modified Brouwer-Lyddane model with drag was used for the realistic orbit prediction, the CZCS pigment concentrations were used to compute water-leaving radiances, and a variety of radiative transfer models were used to calculate atmospheric contributions to total radiances detected by OSMI. Imagery of the simulated OSMI radiances for 412, 443, 490, 555, 765, 865nm was obtained. As expected, water-leaving radiances were only a small fraction (below 10%) of total radiances and sun glint contaminations were observed near the solar declination. Therefore, atmospheric correction is critical in the calculation of pigment concentration from total radiances. Because the imagery near the sun's glitter pattern is virtually useless and must be discarded, more advanced data collection planning will be required to succeed in the mission of OSMI which is consistent monitoring of global oceans during three year mission lifetime.

• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.1-9
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• 2011

The Communication Ocean and Meteorological Satellite(COMS), the first geostationary observation satellite, was successfully launched on June 27th in 2010. The raw data of Meteorological Imager(MI) and Geostationary Ocean Color Imager(GOCI), the main payloads of COMS, is delivered to end-users through the on-ground processing. The COMS Image Data Acquisition and Control System(IDACS) developed by Korea Aerospace Research Institute(KARI) in domestic technologies performs radiometric and geometric corrections to raw data and disseminates pre-processed image data and additional data to end-users through the satellite. Currently the IDACS is in the nominal operations phase after successful in-orbit testing and operates in National Meteorological Satellite Center, Korea Ocean Satellite Center, and Satellite Operations Center, During the in-orbit test period, validations on functionalities and performance IDACS were divided into 1) image data acquisition and transmission, 2) preprocessing of MI and GOCI raw data, and 3) end-user dissemination. This paper presents that IDACS' operational validation results performed during the in-orbit test period after COMS' launch.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.10a
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• pp.83-88
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• 2003

An analytical study was carried out to evaluate the regenerative cooling characteristics in the liquid rocket engine of a 10tf-thrust level using kerosene as a fuel. As a supplementary cooling method, a radiative cooling was applied to the nozzle extension. It was found out from this work that the cooling system with the regenerative and radiation cooling only is not adaptable as a cooling method for the liquid rocket engine of a 10tf-thrust level using kerosene as a fuel for the 2nd stage of the space launch vehicle. So, additional cooling method, curtain cooling was introduced and analyzed. Curtain cooling was very effective to reduce the thermal and thermo-structural instability.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.3
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• pp.109-117
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• 2006

Hot firing performance test of hydrazine decomposition catalyst used for monopropellant thruster of satellite and launch vehicle was performed on the ground. A test equipment for hot firing performance measurement of catalyst test was developed in collaboration with Hanwha Corp., and the catalyst firing performance were tested with the equipment. After a reaction delay time, a catalyst activity and a granule stability were measured for 2 times, satisfactory results were obtained such as 25msec, 2%, $704^{\circ}C$ for each test items on the average. In addition, the current development status of domestic prototype catalyst and its decomposition performance test results are presented.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.10
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• pp.738-746
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• 2019

Instead of hydraulic actuation systems, an electromechanical actuation system is more efficient in terms of weight, cost, and test evaluation in the thrust vector control of the 7-ton gimbal engine used in the Korea Space Launch Vehicle-II(KSLV-II) $3^{rd}$ stage. The electromechanical actuator is a kind of servo actuator with position feedback and uses a BLDC motor that can operate at high vacuum. In the case of the gimballed rocket engine, a synthetic resonance phenomenon may occur due to a combination of a vibration mode of the actuator itself, a bending mode of the launcher structure, and an inertial load of the gimbals engine. When the synthetic resonance occurs, the control of the rocket attitude becomes unstable. Therefore, the requirements for the stiffness have been applied in consideration of the gimbal engine characteristics, the support structure, and the actuating system. For the 7-ton gimbal engine of the KSLV-II $3^{rd}$ stage, the stiffness requirement of the actuation system is $3.94{\times}10^7N/m$, and the direct drive type electromechanical actuator is designed to satisfy this requirement. In this paper, an equivalent stiffness analysis model of a direct drive electromechanical actuator designed based on the stiffness requirements is proposed and verified by experimental results.

• Aerospace Engineering and Technology
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• v.10 no.1
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• pp.107-115
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• 2011

The line-telemetry data processing system is necessary for monitoring the status of each onboard systems of KSLV-I upper stage during the ground tests and launch preparation. The mission of line-telemetry system is to provide reference telemetry data and to monitor the status of upper stage. The line-telemetry data processing system consists of a PCM acquisition/processing server, a system management server, and 9 monitoring consoles. In this paper, we will describe the overview of onboard remote measurement system, the design of the line-telemetry data processing system, anomaly setup information for indicating alarm signal in case of abnormal occurrence, and the result of the ground test and flight test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.10
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• pp.867-875
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• 2018

Conventional nylon wire cutting-type holding and release mechanisms (HRMs) are limited to securely hold the solar panel under launch environment as the size of the panel increases because the nylon wire is tightened directly on the surface of the solar panel. In this study, we proposed a nylon wire cutting-type HRM for 6U CubeSat's solar panel applying elliptic-shaped bracket with a Ball & Socket interface. The proposed HRM has the advantage of higher holding capability along in-plane and out-of plane directions of solar panel and simplicity in tightening process of nylon wire. The design drivers of structural design of CubeSat's solar panel with the proposed HRM were defined by structural analysis under launch loads. In addition, The design effectiveness of the proposed HRM was verified through the functional tests according to the thickness of nylon wire and the number of wire winding under various temperature conditions.

• Aerospace Engineering and Technology
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• v.13 no.1
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• pp.96-107
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• 2014

Korea Aerospace Research Institute has a plan to launch experimental lunar orbiter in 2017, and lunar orbiter and lander in 2020. In the mission planning phase, LOI(Lunar Orbit Insertion) maneuver strategy should be designed using finite burn model because on-board propulsion system of lunar orbiter in finite burn type. LOI maneuver plan and amount of required ${\Delta}V$ using finite burn model depend on the spacecraft attitude at burn, a type of propellant, thrust level and burn timing. This paper describes the LOI maneuver of lunar orbiter of foreign space agency and then comes up with the LOI maneuver plan of Korean lunar orbiter. Adequate thrust level and burn duration of Korean lunar orbiter also present by performing simulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.4
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• pp.56-62
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• 2013

The system analysis and design program of the liquid rocket engine has been developed for preliminary conceptual design process. The program analyzes the engine system and obtains optimal design variables by optimization methods such as genetic algorithm for the higher specific impulse and thrust to weight ratio using given input parameters and requirements. For the users' convenience, the GUI has been offered. The 3-dimensional model for the visualization of results has been interconnected with the CATIA program. The results are expected to be applied to the design process of the space launch vehicle for the analysis and selection of the propulsion system.