• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.544-551
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• 2014

A program of launch vehicle performance analysis is composed for the education of the conceptual design of launch vehicles and the requirement analysis for the propulsion system design. The program is applied for the mission analysis of space launch vehicles based on KSLV-II with liquid rocket boosters. The 75-ton class liquid rocket engine is assumed for the boosters by referring the mass ratio of KSLV-II second stage. The launch performance analysis is carried out for KSLV-II with 2, 3 and 4 boosters by targeting the circular orbit of 700 km altitude. The trajectory is assumed as two-dimension considering the variation of the flight environment. Payload of advanced KSLV-II could be increased to maximum 3 tons, though it is limited by the thrust performance of the upper stage.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.683-691
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• 2014

Significance of SAR(Synthetic Aperture Radar) satellite regadless of weather have grown for Earth observation. According to the cost-effective trend in satellite development, SAR antenna is actively studied. It's a competitive candidate to use deployable SAR antenna out of CFRP. In this study, variables for an antenna configuration model was researched and evaluated. The design of the antenna was structurally analyzed by FEM(Finite Element Model). Tool-kit was developed for modifying the SAR antenna model easily in accordance with system requirement change. In the tool-kit, antenna configuration design and error analysis of the antenna surface could be achieved. And compatibility of tool-kit results to CST, a RF analysis program, was confirmed.

• Journal of Astronomy and Space Sciences
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• v.25 no.4
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• pp.491-504
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• 2008

CSSA (Coarse Sun Sensor Assembly) is the essential sensor for satellite attitude control. CSSA measures the direction of the sun's rays and determines whether the satellite is in the ellipse. The paper shows the development process and test results of Path-finder & Qualified Model CSSA as the preceding development in order to develop the CSSA for low earth orbit satellite. We needs the definite and precision procedure and lots of experience. This paper shows that we can improve those through the development of Path-finder and Qualified Model CSSA. Therefore, we can obtain the results to meet the functional requirement.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.1
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• pp.1-8
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• 2013

A liquid-monopropellant hydrazine thruster has several outstanding advantages such as relatively-simple structure, long/stable propellant storability, clean exhaust products, and so on. Therefore hydrazine thruster has such a wide application as orbit and attitude control system (ACS) for space vehicles. A hydrazine thruster with the medium-level thrust to be used in the ACS of space launch vehicles (SLV) has been developed, and its ground firing test result is presented in terms of thrust, impulse bit, temperature, and chamber pressure. It is verified through the performance test that the response and repeatability of thrust are very excellent, and the thrust efficiencies compared to its ideal requirement are larger than 93%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.12
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• pp.4835-4855
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• 2015

TV white space (TVWS) is showing promise to become the first widespread practical application of cognitive technology. In fact, regulators worldwide are beginning to allow access to the TV band for secondary users, on the provision that they access the geolocation database. Device-to-device (D2D) can improve the spectrum efficiency, but large-scale D2D communications that underlie TVWS may generate undesirable interference to TV receivers and cause severe mutual interference. In this paper, we use an established geolocation database to investigate the power allocation problem, in order to maximize the total sum throughput of D2D links in TVWS while guaranteeing the quality-of-service (QoS) requirement for both D2D links and TV receivers. Firstly, we formulate an optimization problem based on the system model, which is nonconvex and intractable. Secondly, we use an effective approach to convert the original problem into a series of convex problems and we solve these problems using interior point methods that have polynomial computational complexity. Additionally, we propose an iterative algorithm based on the barrier method to locate the optimal solution. Simulation results show that the proposed algorithm has strong performance with high approximation accuracy for both small and large dimensional problems, and it is superior to both the active set algorithm and genetic algorithm.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.36.2-36.2
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• 2010

The CQUEAN (Camera for QUasars in EArly uNiverse) is an optical CCD camera optimized for observation of high redshift objects. It is going to be attached to the cassegrain focus of 2.1m telescope at McDonald Observatory, USA. We are making a focal reducer for CQUEAN to secure a larger field of view. The focal reducer is composed of four spherical lens, and it reduces the focal length of telescope by one third. We designed the lens configuration, performed tolerance analysis, and estimated the optical performance with ZEMAX. The differences in optical performace with/without filters were also investigated. The result from ZEMAX shows that the system has ample margin of errors for median seeing of 1.2" at McDonald observatory. Even with aberration and alignment tolerance, the performance is better than the original requirement. The lenses are now being made, and the lens barrel and an adapter for assembly of the Andor CCD camera and the filter wheel is now under designing process. We expect that the manufacturing of the focal reducer system as well as its optical test will be finished by April 2010.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.2
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• pp.114-123
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• 2017

Little Intelligent Nanosatellite of KAIST(LINK) is a 2U-size CubeSat which is developed by Aerospace Systems & Control Lab.(ASCL) of KAIST as a part of the international cooperation project QB50. The objective of the QB50 project is to carry out atmospheric research within the lower thermosphere and ionosphere and CubeSats are planned to be deployed at the International Space Station(ISS) from the first quarter of 2017. To implement this objective, a flight model(FM) of LINK has been successfully developed and the design and performance of the satellite have been verified by performing environment and function tests in accordance with acceptance requirement level. This paper describes the development of flight model and the results of vibration and thermal vacuum test.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.2
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• pp.216-224
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• 2000

The spatial layout planning system allocates rectangular resources in the limited space according to user requirements, This system also can optimizes the spatial allocation problem to maximize the user's requirement. The spatial layout planning Problems for this system can be solved by searching a wide area of space since this problem entails the non-polynomial algorithm. By accommodating the user's dynamic requirements, the modification of a specific space and the redesign of the whole area can be accomplished. In this paper, the spatial layout planning problem is solved efficiently with a resource allocation method based on CSP. The dynamic constraints by adding user requirements are accommodated through the intelligent user Interface. The 3-D layout on the web environment by using VRML is also shown for providing for the visual verification of the 2-D layout and, thereafter, the additional modification of the 2-D layout.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.2
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• pp.172-178
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• 2015

The control moment gyroscope(CMG) which is well known as an effective high-torque-generating device is applicable to space vehicles, airplanes, ships, automobiles, robotics, etc. for attitude stabilization and maneuver. This paper deals with the overall details of 100Nm-class CMG development for various industrial applications, and provides the activities and results associated with the CMG system-level requirement analysis, the motor subsystem design/manufacturing/integration, the construction of ground support equipment, and the performance test and evaluation. The performance test reveals that the CMG generates the torque output more than 120Nm in as-designed operation of spin motor and gimbal motor.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.313-318
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• 1998

Electro-Optical Camera(EOC) is the main payload of Korea Multi-Purpose SATellite(KOMPSAT) with the mission of cartography to build up a digital map of Korean territory including Digital Terrain Elevation Map(DTEM). This instrument which comprises EOC Sensor Assembly and EOC Electronics Assembly produces the panchromatic images of 6.6 m GSD with a swath wider than 17 km by push-broom scanning and spacecraft body pointing in a visible range of wavelength, 510 ~ 730 nm. The high resolution panchromatic image is to be collected for 2 minutes during 98 minutes of orbit cycle covering about 800 km along ground track, over the mission lifetime of 3 years with the functions of programmable rain/offset and on-board image data storage. The image of 8 bit digitization, which is collected by a full reflective type F8.3 triplet without obscuration, is to be transmitted to Ground Station at a rate less than 25 Mbps. EOC was elaborated to have the performance which meets or surpasses its requirements of design phase. The spectral response the modulation transfer function, and the uniformity of all the 2592 pixel of CCD of EOC are illustrated as they were measured for the convenience of end-user. The spectral response was measured with respect to each gain setup of EOC and this is expected to give the capability of generating more accurate panchromatic image to the EOC data users. The modulation transfer function of EOC was measured as greater than 16% at Nyquist frequency over the entire field of view which exceeds its requirement of larger than 10%, The uniformity that shows the relative response of each pixel of CCD was measured at every pixel of the Focal Plane Array of EOC and is illustrated for the data processing.