• Composites Research
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• v.15 no.3
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• pp.30-38
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• 2002

Fiber Bragg grating(FBG) like other optical fiber sensors also has the merit of embedding capability. To increase their actual value related to embedding capability, this paper reported the reliability and signal characteristics of FBGS embedded in composite laminates. The microphotographs of embedded optical fibers visualized the embedding environments of stripped optical fibers and coated optical fibers. Based on these microphotographs and cure monitoring performed using FBGs, we could understand that the main cause breaking the unique Bragg condition of low-birefrigence FBG were residual stress artier curing and reported the stale of stress/strain of optical fiber quantitatively. The cure monitoring also showed the history of splitting peak of a stripped FBG along cure processing. In addition, we could obtain a transverse insensitive grating(TIG) with ease by recoating a stripped FBG. TIG has good advantage for real-time signal processing.

• Korean Journal of Remote Sensing
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• v.27 no.2
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• pp.89-98
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• 2011

Four kinds of gain and offset correction coefficients that are used to correct the nonuniformity between pixels are discussed. And their correction performance has been compared by performing image correction. using the correction coefficients calculated, on the real image data obtained from a newly fabricated camera electronics system. The performance of the correction coefficients depends in general on the number of the light input levels used to obtain the reference image. The result shows that, as expected obviously, when only two light input levles are used to obtain the reference image, even though its correction coefficients are relatively easily calculated, the correction performance is relatively poor. And with the number of light inputs increased to a value of larger than two, the correction performance is improved. It is noted, however, no Significant performance difference is found between the different correction coefficients employed.

• Korean Journal of Remote Sensing
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• v.28 no.1
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• pp.39-54
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• 2012

The objective of this study is to propose efficient data fusion techniques feasible to the KOMPSAT-2 satellite images. The most widely used image fusion techniques, which are the high-pass filter (HPF), the intensity-hue-saturation-based (modified IHS), the pan-sharpened, and the wavelet-based methods, was applied to four KOMPSAT - 2 satellite images having different regional and seasonal characteristics. Each fusion result was compared and analyzed in spatial and spectral features, respectively. Quality evaluation of image fusion techniques was performed in both quantitative and visual analysis. The quantitative analysis methods used for this study were the relative global dimensional error (spatial and spectral ERGAS), the spectral angle mapper index (SAM), and the image quality index (Q4). The results of quantitative and visual analysis indicate that the pan-sharpened method among the fusion methods used for this study relatively has the suitable balance between spectral and spatial information. In the case of the modified IHS method, the spatial information is well preserved, while the spectral information is distorted. And also the HPF and wavelet methods do not preserve the spectral information but the spatial information.

• Korean Journal of Remote Sensing
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• v.34 no.2_1
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• pp.227-236
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• 2018

The focus control mechanism of the multi-purpose camera can be required for the better quality image acquisition. A good image acquisition through the hardware system including the optics and image sensor, has to be processed before the post correction for improvement of image quality. In the case of the high-resolution satellite camera, the focus control is not a necessity, unlike a normal camera due to a fixed optical system, but may be required due to various reasons. Although there is a basic focus control method using a motor for satellite electronic optical camera, a focus control method using thermal control can be a good alternative because of its various advantages in design, installation, operation, contamination, high reliability and etc. In this paper, we describe the design method and implementation results for the focus control mechanism using the temperature sensor and heater installed in the telescope structure. In the proposed focus control method, the measured temperature information is converted into temperature data by the Kalman filter and the converted temperature data are used in PI controller for the thermal focus control.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.2
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• pp.124-132
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• 2018

In this paper, landing stability evaluation of lunar lander considering various landing conditions was performed. The status of landing stability of the lunar lander is classified into stable landing, conditionally stable landing due to sliding and unstable landing due to tip-over. In particular, the quasi-static tip-over equation was rearranged considering the phenomena of lowering the center of gravity and extension of foot-pad interval of the landing gear. These results were compared by finite element model analysis results using a commercial software ABAQUS and its validity and accuracy were verified. The verified finite element model was used for examining the tendency of various environmental variables such as landing conditions, friction coefficient, lateral speed and slope of ground.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.7
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• pp.583-591
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• 2018

In this paper, we propose a new deployment test equipment that is characterized for the deployment test of single large solar panel with tape spring hinge. To perform the deployment test on ground, a device that takes gravity compensation into account should be used to create a zero gravity environment similar to that in orbit. We analyzed the advantages and disadvantages of the most commonly used deployment test equipment in the past through simple conceptual design, analysis, and tests to judge whether it is applicable to the deployment of the solar panel to be tested. A dummy frame was proposed to reduce the air drag effect during on-ground test and a self-aligning ball bearing and adjusting screws were applied to the deployment test equipment to solve the alignment problem with the gravity axis. And a horizontal bearing for radial movement applied to compensate for the change of the axis of the tape spring hinge. From these, we solved the problems of the conventional deployment test equipment by developing and verifying the new deployment test equipment characterized for the solar panel to be deployed in this paper.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.7
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• pp.551-556
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• 2018

A lot of hardwares are allocated on the satellite to perform the attitude control. Sun sensor is very important hardware to acquire the initial attitude after separation from launcher and to maintain the safety attitude from the satellite anomaly operation. So the allocation of the sun sensor to acquire the field of view and the attitude control design using it, are critical work in the beginning of development. Number of Sun sensor for GEO-KOMPSAT2 is reduced with respect to COMS due to star tracker usage. The additional sun sensor using COMS heritage is considered. In this paper, it is described the analysis and the results on the method for the safety improvement which is to enlarge the field of view and to consider the harness connection of P/R-side of the sun sensor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.10
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• pp.856-867
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• 2018

This paper presents the applicability of MIMO joint decoding to dual-contact satellite systems in which two LEO satellites using X-band frequency band are transmitting each image data to two ground station antennas, simultaneously. When two satellites are closely positioned within the looking angle of the two antennas, each satellite interferes with each other by the relative antenna gain corresponding to an offset angle and this might cause the performance degradation without interference mitigation. To mitigate the performance degradation, SM MIMO techniques for joint decoding are applied. Especially, the relative antenna gain of ground station depending on the angle difference between two satellites in ground station antenna plays an important role in modelling the dual-contact satellite systems. The condition number of MIMO channel including the antenna gain calculated from the mathematical gain pattern model was primarily analyzed. Simulation results showed that the SM MIMO techniques using detection schemes such as ZF-SIC, MMSE-SIC, and ML can be applicable to dual-contact satellite systems.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.674-682
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• 2014

Radio Frequency Test Set (RFTS) is essential to verify Telemetry, Command & Ranging (TC&R) RF subsystem of both Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO) satellite during Assembly Integration & Test (AI&T). The existing RFTS was specialized for each project and needed to be modified for each new satellite. The new design enables RFTS to be used in various projects. The hardware and software was designed considering this and therefore it could be directly used in other projects within a similar test period without modification or inconvenience. It will be also easily controlled, modified, and managed through the extension in modularization according to each function and the use of COTS (commercial on-the-self) and this will improve system reliability. A more reliable RF test measurement is also provided in this new RFTS by using an accurate reference clock signal.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.8
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• pp.718-727
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• 2016

Korean ground systems have started to be developed for mission control and payload data processing since 1990s. International technology cooperations were needed in the early development phase of ground system for science experiment satellite, LEO satellite and GEO satellite and then they have been developed as domestic own technology since acquiring early technology. Our country has developed total 14 ground systems until now, this paper suggests prospect and direction on ground system development in the base of such development experiences. Mission control system is needed to develop multi-satellite mission control system in the base of technology of re-configure, re-use and automation. Processing system is needed to acquire processing technology for kinds of payload sensor data and study inter-operation to integrate and use outputs which are processed between users. Finally, national ground system infrastructure is needed to operate kinds of lots of satellites at worldwide area.