• Journal of Industrial Technology
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• v.35
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• pp.55-58
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• 2015

Natural shifting of rivers has been disturbed by anthropological activities. Urbanization in Kathmandu has been encroached the natural floodplain of Bagmati and currently channeled by training walls. The study compares the change in shape of Dhobikhola, a small tributary using 1966 and 2014 satellite images. It has been found that the original shape is heavily changed over time at the beginning and end section of river under study. The river width is now fixed by training walls and roads along the banks. Using multiple data sets like satellite images and GIS analysis, these shifts can be easily detected to plan for management and restoration of physical and ecological behaviors of rivers.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.74-75
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• 2013

Pseudolite is a contraction of the term "pseudo-satellite," used to refer to something that is not a satellite which performs a function commonly in the domain of satellites. Pseudolite are most often small transceivers that are used to create a local, ground-based GPS alternative. This paper proposes a clock synchronization scheme for pseudolite.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.9
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• pp.481-487
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• 2004

The Ku band that has been using for the satellite communication and broadcasting would be changed to K/Ka bands. The satellite system requires the antenna structure to fabricate low loss and small antenna that is able to be integrated with other Rf circuits for both Rx and Tx. So we should design it with dual feed antennas at K/Ka bands, high isolation between two different feeds and broadband circular polarization. This paper proposes the LTCC(Low Temperature Co-fired Ceramic) process for integration with other Rf circuits and the Axial mode of the helical antenna to satisfy those requirements.

• Ocean and Polar Research
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• v.23 no.2
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• pp.133-139
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• 2001

Ocean currents estimated from sea height anomalies derived from inter-calibrated TP/ERS are compared with daily mean currents measured with satellite-tracked drifters. The correlation coefficient between the geostrophic current from TP/ERS and surface current at 15 m depth from drifter tracks was found to be about 0.5. Due to the limitation of satellite ground tracks, small scale eddies less than 80 km are poorly resolved from TP/ERS. One of the interesting results of this study is that coastal currents along the eastern coast of Korea were well reproduced from sea height anomalies when the coastal currents were developed in association with eddies near the South Korean coast. The eddy kinetic energy (EKE) estimated from drifters, TP/ERS, and a numerical model are also compared. The EKE estimated from drifters was about 22 % higher than EKE calculated from TP/ERS. The pattern of low EKE level in the northern basin and high EKE level in the southern East Sea is shown in the EKE estimates derived from both the drifters and TP/ERS.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.1
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• pp.64-70
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• 2008

Thanks to the breakthroughs in micro fabrication technology, numerous concepts of micro aerospace systems including micro aerial vehicle, nano satellite and micro robot have been proposed. In order to activate these mobile micro systems, high density power in a small scale power source is required. However, we still do not have micro power source that has energy density that can support these systems. In the present article, status of micro power sources are described and alternatives that have been derived from the past experience are proposed.

• Journal of Astronomy and Space Sciences
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• v.19 no.3
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• pp.225-230
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• 2002

Synthetic Aperture Radar (SAR) has been used for mapping the surface geomorphology of cloudy planets like Venus as well as the Earth. The cloud-free Mars is also going to be scanned by SAR in order to detect buried water channels and other features under the very shallow subsurface af the ground. According to the 'Mid and Long-term National Space Development Plan' of Korea, SAR satellites, in addition to the EO (Electro-Optical) satellites, are supposed to be developed in the frame of the KOMPSAT (Korean Multi-Purpose Satellite) program. Feasibility of utilizing a SAR payload on KOMPSAT platform has been studied by KARI in collaboration with Astrium U.K. The purpose of the ShR program is Scientific and Civil applications on the Earth. The study showed that KOMPSAT-2 platform can accommodate a small SAR like Astrium’s MicroSAR. In this paper, system aspects of the satellite design are presented, such as mission scenario, operation concept, and capabilities. The spacecraft design is also discussed and conclusion is followed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.537-544
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• 2004

In this paper, we p개pose DS-CDM-SQAM(Superposed Quadrature Amplitude Modulation) which is characterized by its smooth phase transition and small envelope fluctuation, and improves the power efficiency as compared to DS-CDM-QPSK of satellited-based DMB system(ITR-R BO.1130-4 System E) in a nonlinearly amplified channel. Computer simulation results show that the proposed DS-CDM-SQAM improves Eb/No by 1.7㏈ to maintain BER=1${\times}$$10^{-3}$ in nonlinearly amplified multipath mobile radio environments. Therefore, the proposed DS-CDM-SQAM system significantly improves the power efficiency in nonlinear land mobile satellite DMB environments.

• International Journal of Aeronautical and Space Sciences
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• v.5 no.1
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• pp.6-18
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• 2004

This paper addresses the development and design of the HAUSAT-l (Hankuk Aviation University SA'Tellite-D communication subsystem, which is a next generation picosatellite, developed by SSRL (Space System Research Lab.) of Hankuk Aviation University. The communication subsystem generally consumes the majority of power and volume for picosatellites, and thus its design is critical to the overall satellite and mission plans. The HAUSAT-l designs are implemented by using the 145.84 MHz for uplink and 435.84 MHz for downlink frequency bands. The simulation and test results of the homemade radio and the TNC (Terminal Node Controller) integrated on the HAUSAT - I , a picosatellite scheduled to launch on September 2004 by Russian launch vehicle "Dnepr", are presented for EM, QM and FM, respectively.

• Journal of electromagnetic engineering and science
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• v.15 no.2
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• pp.111-114
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• 2015

In this paper, we have proposed dual-band Phi-shaped slot gap filler antenna for satellite internet service applications. Some properties of the antenna such as return loss, radiation pattern, and gain have been simulated and measured. The proposed antenna has a Phi-shaped slot on the circular patch and is fabricated on the TLX-9 substrate. The radius of the circular patch is 25 mm, and it has a coaxial feeding structure. The dual-band Phi-shaped slot gap filler antenna has high-gain, small-size, simple-structure, and good radiation patterns at each band. The operating frequency band can be tuned by adjusting the length AL and FL of the Phi-shaped slot.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1280-1285
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• 2004

Microsystem technology has been applied to space technology and became one of the enabling technology by which low cost and high efficiency are achievable. Micro propulsion system is a key technology in the miniature satellite because micro satellite requires very small and precise thrust force for maneuvering and attitude control. In this paper research on micro solid propellant thruster is reported. Micro solid propellant thruster has four basic components; micro combustion chamber, micro nozzle, solid propellant and micro igniter. In this research igniter, solid propellant and combustion chamber are focused. Micro igniter was fabricated through typical micromachining and evaluated. The characteristic of solid propellant was investigated to observe burning characteristic and to obtain burning velocity. Change of thrust force and the amount of energy loss following scale down at micro combustion chamber were estimated by numerical simulation based on empirical data and through the calculation normalized specific impulses were compared to figure out the efficiency of combustion chamber.