• Proceedings of the KSME Conference
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• 2005.11a
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• pp.145.2-145.2
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• 2005

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.77-80
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• 2002

Thermal analysis has been performed to evaluate the thermal effect on composite antenna (Ka-band) structure in space environment. The concepts of thermal control are also presented to maintain the antenna components within respective temperature limits. A steady-state algorithm of I-DEAS' thermal analysis software was utilized to predict both maximum and minimum temperature, maximum gradient temperature, and temperature distribution on each antenna component.

• Journal of computational fluids engineering
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• v.20 no.4
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• pp.63-69
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• 2015

The thermal balance test in vacuum chamber for satellite structures is an essential step in the process of satellite development. However, it is technically and economically difficult to fully replicate the space environment by using the vacuum chamber. To overcome these limitations, the thermal analysis through a computer simulation technique has been conducted. The CFRP composite material has attracted attention as satellite structures since it has advantages of excellent mechanical properties and light weight. However, the nonuniform nature of the thermal conductivity of the CFRP structure should be noted at the step of thermal analysis of the satellite. Two different approaches are studied for the thermal analyses; a detailed numerical modeling and a simplified model expressed by an effective thermal conductivity. In this paper, the effective thermal conductivities of the CFRP composite structures are extracted from the detailed numerical results to provide a practical thermal design data for the satellite fabricated with the CFRP composite structure. Calculation results of the surface temperature and the thermal conductivities along x, y, z directions show fairly good agreements between the detailed modeling and the simplified model for all the cases studied here.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.161-164
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• 2005

This paper finds the optimal staking sequence of the satellite composite structures to minimize severe thermal deformations during their orbital operation using GAs and finite element analyses. Then, the optimal design is reinforced to endure the launch loads like high inertia and vibratory loads that are, usually, smaller than orbital loads induced by space environments. The thermal deformation of sandwich panels was minimized at the staking sequence of [$0_2$/90]s and that of composite strut was lowest at the angle of [0/${\pm}45$]s Also there was no buckling in the compressive loading. By vibration analysis, the natural frequencies of the composite components are much higher than aluminum structures and the expected stiffness condition is satisfied. Then, a composite optical bench was fabricated for tests and all analyses results were verified by structural testing. There were good correlations between two results.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.119-122
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• 2002

The vibration qualification test of satellite antenna is required to verify that there will be no structural damage due to the severe vibration caused by the launch of satellite. For the qualification test, reasonable test load condition needs to be introduced by dynamic analysis. The present work has been performed to provide an understanding how the qualification test load can be evaluated by the results of both normal mode and sine vibration analyses with notching technique for a composite Ka-band antenna structure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.586-594
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• 2009

This paper is the study on random, sinusoidal and shock vibration responses for the STSAT-3(science and technology satellite-3) proto-model which is the first small size all-composite satellite in Korea. The structure system of the STSAT-3 forms box type structure by joining several hybrid sandwich panels comprised of honeycomb core and carbon fiber reinforced laminated composite skins on both side. Mode shape, stress, displacement and acceleration responses are obtained on both the frequency domain and time domain by means of a commercial FEA software MSC/NASTRAN. From these analysis results, failure, safety factor and design validity are assessed. These results can be successfully applicable as reference data when a new satellite is developed as well as giving out an excellent criteria in satellite vibration treatment design.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.479-482
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• 2004

Laminate Design of a composite tube for a space telescope(Fig. 1) under hygrothermal load is studied. Carpet plots for laminate effective engineering constants are generated and used for selecting the best tube lay-ups satisfying the optomechanical requirements for a space telescope being dimensional1y stable under orbital thermal loading. Despace of the tubes constructed with the selected lay-ups are calculated with a Zig-Zag Triangular Element which accurately represents through thickness stress variations for laminated structures. The effects of moisture absorption when exposed to humidity environment and moisture desorption through outgassing on the dimensional stability are also investigated.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.12
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• pp.975-986
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• 2013

This paper dealt with the fabrication and performance evaluation of the electronics housing made of lightweight composite materials, aiming at the enhancement of satellite mass savings by replacing conventional aluminum alloy widely used for satellite avionics with lightweight composite material. For this purpose, a fabrication process was designed to overcome low machinability of CFRP and to minimize the post-treatment. The composite housing with grid-stiffened and monolithic frame was made using co-curing method. Its performance was also evaluated regarding endurance, stiffness, thermal conductivity, electrical grounding, EMI protection and radiation shielding. The composite housing can provide the considerable mass savings over the aluminum housing with same dimension.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.13-18
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• 2001

This paper deals with finite element analysis for free vibration and forced sine vibration of Ka- and Ku- bend antenna structures using MSC/PATRAN/NASTRAN. The structures are designed to satisfy minimum resonance frequency requirement in order to decouple the dynamic interaction of the satellite with the spacecraft bus structure. From the forced sinusoidal vibration, we have observed output acceleration versus input in X-,Y- and Z- direction, based on base excitation using large mass method. The results of finite elements analysis can be used as the reference data for the experimental test of satellite antenna, resulting in the reduction of cost and time by predicting and complementing experimental data.

• Korean Journal of Remote Sensing
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• v.32 no.1
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• pp.25-38
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• 2016

With the increasing need for high temporal resolution satellite imagery for monitoring land surfaces, this study evaluated the temporal resolution of the NDVI composites from Geostationary Ocean Color Imager (GOCI) data. The GOCI is the first geostationary satellite sensor designed to provide continuous images over a $2,500{\times}2,500km^2$ area of the northeast Asian region with relatively high spatial resolution of 500 m. We used total 2,944 hourly images of the GOCI level 1B radiance data obtained during the one-year period from April 2011 to March 2012. A daily NDVI composite was produced by maximum value compositing of eight hourly images captured during day-time. Further NDVI composites were created with different compositing periods ranging from two to five days. The cloud coverage of each composite was estimated by the cloud detection method developed in study and then compared with the Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua cloud product and 16-day NDVI composite. The GOCI NDVI composites showed much higher temporal resolution with less cloud coverage than the MODIS NDVI products. The average of cloud coverage for the five-day GOCI composites during the one year was only 2.5%, which is a significant improvement compared to the 8.9%~19.3% cloud coverage in the MODIS 16-day NDVI composites.