• Journal of Astronomy and Space Sciences
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• v.23 no.1
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• pp.39-54
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• 2006

HAUSAT-2 is nano satellite with 25kg mass being developed by Space System Research Lab. in Hnakuk Aviation University. This paper addresses HAUSAT-2 small satellite thermal analyses and its verification at satellite system, electronic box, and PCB levels. Thermal model which is used for system-level and box-level thermal analyses was verified and corrected through thermal vacuum/balance test. The new board-level thermal analysis methodology, modelling high-power dissipating EEE parts directly, was proposed. The proposed methodology has been verified with test results.

• Journal of Satellite, Information and Communications
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• v.1 no.1
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• pp.26-39
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• 2006

A synthetic aperture radar (SAR) system can provide all-weather, day and night imaging capability, and thus, is very useful in surveillance for both civil and military applications. In this paper, the X-band spaceborne SAR system design procedure is introduced with the key design parameters for mission and system requirements characterized by the small satellite platform. The SAR imaging mode design technique is presented, and the design results are analyzed for standard mode performance evaluation. In line with the system requirements, the X-band SAR payload and ground reception/processing sub-systems are presented with the key design results and image applications examples. The designed small satellite SAR system shows the wide range of imaging capability, and proves to be an effective surveillance system in light-weight, high-performance and cost-effective points of view.

• Journal of Aerospace System Engineering
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• v.12 no.4
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• pp.75-80
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• 2018

The working principle of a satellite camera involves a focusing mechanism for controlling the focus of the optical system, which is essential for proper functioning. However, research on focusing mechanisms of satellite optical systems in Korea is in the beginning stage and developed technology is limited to a thermal control type. Therefore, in this paper, we propose a motor-driven focusing mechanism applicable to small satellite optical systems. The proposed mechanism is designed to generate z-axis displacement in the secondary mirror by a motor. In addition, three flexure hinges have been installed on the supporter for application of preload on the mechanism resulting in minimization of the alignment error arising due to manufacturing tolerance and assembly tolerance within the mechanism. After fabrication of the mechanism, the alignment errors (de-space, de-center, and tilt) were measured with LVDT sensors and laser displacement meters. Conclusively, the proposed focusing mechanism could achieve proper alignment degree, which can be applicable to small satellite optical system.

• International Journal of Aeronautical and Space Sciences
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• v.4 no.2
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• pp.17-25
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• 2003

Simple methods are developed to predict temperatures of a satellite box during launch stage. The box is mounted on outer surface of satellite and directly exposed to space thermal environment for the time period from fairing jettison to separation. These simple methods are to solve a 1st order ordinary differential equation (ODE) which is simplified from the governing equation after applying several assumptions. The existence of analytical solution for the 1st order ODE is determined depending on treatment of time-dependent molecular heating term. Even for the case that the analytical solution is not available due to the time dependent term, the 1st order ODE can be solved by relatively simple numerical techniques. The temperature difference between two different approaches (analytical and numerical solutions) is relatively small (Jess than $1^{\circ}C$ along the time line) when they are applied to STSAT-I launch scenario. The present methods can be generally used as tools to quickly check whether a satellite box is safe against space environment during the launch stage for the case that the detailed thermal analysis is not available.

• Proceedings of the KIEE Conference
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• 1999.07g
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• pp.3249-3252
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• 1999

In this paper, we present the Tele-PACS of radiology, which uses the communication network as asymetric satellite data communication system. The asymetric satellite data communication system uses receive-only satellite links for data delivery and PSTN(Public Switched Telephone Network) modem or N-ISDN(Integrate Services Digital Network) for communication. The satellite communication linking shows the very high-speed performance than terrestial linking such as 28.8 kbps modem linking and 56Kbps linking. The satellite linking is 5 - 10 times faster than the 56Kbps linking. We conclude that 1) Satellite networking is currently the cheapest and fastest solution for internet access. 2) Web-based Image-Viewer enables small size hospitals in rural area to connect to central PACS easily and to retrieve the image data reliably. 3) The suggested teleradiology system using satellite networking could be adequate to fast telemedicine and telecare for rural hospitals especially located in geographically isolated areas such as islands.

• 전기의세계
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• v.39 no.5
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• pp.27-37
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• 1990

In this paper some of the important trends in the spacecraft technology development have been discussed. Trends of higher satellite radiate power, which involves higher TWTA powers and antenna reconfiguration, and Ka-band (30/20 G $H_{z}$) utilization are discussed. Evolutionary trends in satellite communications in general have demonstrated immense potential for meeting the evolving nees and challenges regarding provision of global telecommunications during over past two decades. Their promise for the coming decades as we enter the 21st century may far surpass our imagination. The expansion of fixed satellite service market will depend upon more inelligent spacecraft and a network of more cost effective small earth stations. Radiation hardened microwave analog technologies and high speed digital technologies are getting ready to meet the challenge posed by future markets. At present commercial satellite communications are going through a trasition period.d.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.12
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• pp.1427-1432
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• 2009

The pitch motion of a generic gravity gradient satellite is investigated in terms of chaos. The Melnikov method is used for detecting the onset of chaotic behavior of the pitch motion of a gravity gradient satellite. The Melnikov method determines the distance between stable and unstable manifolds of a perturbed system. When stable and unstable manifolds transverse on the Poincare section, the resulting motion can be chaotic. The Melnikov analysis indicates that the pitch dynamics of a generic gravity gradient satellite can be chaotic when the orbit eccentricity is small.

• Journal of Astronomy and Space Sciences
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• v.10 no.1
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• pp.17-27
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• 1993

The orbit characteristics and perturbation effects of an artificial satellite with critical inclination have been studied. The critical inclination problem in artificial satellite theory is treated as Ideal Resonance Problem(IRP). The KITSAT-1 satellite launched by Arian 42P at Guiana in August 11, 1992 has orbital inclination close to the critical value cos-1(1/√5). In that case, there is a singularity in some perturbation terms and perigee of the orbit is fixed because d$\omega$/dt is theoretically equal to zero. But actually the long periodic behaviour in argument of perigee, $\omega$ shows a small oscillation. The causes of the oscillation and the relativistic effect in IRP have been studied and applied to the KITSAT-1. The geo-potential perturbation terms which are seperated inclination terms have been obtained using Algebraic manipulation. Also luni-solar disturbing funtion based on the relative position of the sun, moon, and satellite has been obtained. Phase portraits are used to depict the change of eccentricity and grgument of perigee. The variations of each orbital elements have been obtained in case of the KITSAT-1.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.45-48
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• 2002

Satellite image processing software should be able to support interoperability that is to enable consumers, citizens, large and small businesses and governments to make the fullest possible use of the world's spatial data and spatial processing resources. The goal of interoperability is to perform hands-on research, development, testing, fielding, and validation of potential and existing interoperable geoprocessing technologies. In this paper, component based architecture for fast interoperability is designed to maximize interoperability among the OpenGIS components specified in the OpenGIS abstract specifications and implementation specifications and to mix up the OpenGIS components and the fast access mechanism for high performance.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1292-1294
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• 2003

This paper presents the results of research and analysis with the satellite-derived snow data. It provides the main climatic characteristics of snow cover in China and shows the variation and distribution of snow in regions of Xinjiang, Inter Mongolia and Tibet plateau. The study reveals the vicissitude periods of winter snow cover in Tibetan Plateau by using wavelet analysis with the data from 1980 to 2001. It has about 10 years large period and 3-5 years small period. The analysis shows that the extension of snow increased in recent years in Xinjiang. The results of analysis proves the relationship between winter snow cover in Tibetan Plateau and next summer precipitation in the middle and lower reaches of the Yangtze River. They have good correlation.