• 한국항공우주학회지
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• 제35권2호
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• pp.171-176
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• 2007

이동체와의 통신은 항상 안테나가 이동체의 방향을 지향하고 있어야 한다. 본 연구에서는 안테나가 이동체를 지향하기 위해서 사용되는 방식중 이동체의 위치를 측정하여 이동체와 안테나 사이의 기하학적 위치관계로부터 안테나의 지향각을 결정하는 방법을 사용하였다. 안테나와 무인항공기에 각각 GPS를 설치하여 각각의 위치를 측정하고 계산된 지향각을 향하도록 안테나를 구동하였다. 안테나의 지향각과 일치시켜 설치한 카메라를 사용하여 무인항공기를 촬영하여 추적 안테나 시스템의 성능을 검증하였다

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.290-293
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• 2006

COMS (Communication, Ocean and Meteorological Satellite) shall be operated with two remote sensing payloads, MI (Meteorological Imager) and GOCI (Geostationary Ocean Color Imager). Since both payloads have rotating mechanisms, the dynamic coupling between two payloads is very important considering the pointing stability during GOCI operation. In addition, COMS adopts a single solar wing to improve the image quality, which leads to the unbalanced solar pressure torque in COMS. As a result, the off-loading of the wheel momentum needs to be performed regularly (2 times per day). Since the frequent off-loading could affect MI/GOCI imaging performance, another suboptimal off-loading time needs to be considered to meet the AOCS design requirements of COMS while having margin enough in the number of thruster actuations. In this paper, preliminary analysis results on the pointing stability and the wheel off-loading time selection with respect to MI/GOCI operations are presented.

• 전자공학회논문지A
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• 제32A권10호
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• pp.64-72
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• 1995

In this paper, atmospheric turbulence and absorption under clear weather condition, which affect the optical satellite up-link communication between geo-satellites and earth station, were studied. In case of the up-link communication, the received optical power is weakened by pointing loss caused by beam tilt which is the main effect of turbulent atmosphere. This pointing loss directly has relation to the diameter of optical transmitting antenna. From the inverse proportion of the pointing and spaced loss, it is the regions where the diameter of transmitting antenna increases abruptly and the efficient design of transmitting antenna is impossible. In case of using channel coding, it was shown that the peak value of diameter moved to the lower regions of elevation angle with increasing the coding gain and its width was also decreased. In case of considering both coding gain and transmission rate on the design of transmitting antenna, it was known that more coding gain was necessary as transmission rate was increased.

• 천문학논총
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• 제14권1호
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• pp.47-56
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• 1999

We have improved the control and driving system of 16' reflector at Kwanak Observatory at Seoul National University, by completing encoder unit, and by developing programs for correction of errors resulting from hardware defects. The hardware defects of this telescope system are the large backlash and the nonuniform tracking and pointing. The telescope pointing accuracy for RA is improved to a few arc minutes, and that for DEC is several tens of arc minutes. The guiding error is improved to 0.7 arcsec/minute, allowing up to 3 minutes exposure for CCD imaging under typical seeing conditions at the Observatory.

• 한국군사과학기술학회지
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• 제1권1호
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• pp.65-81
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• 1998

Objective technology development has been carried out aiming performance improvement of the stabilized gun-pointing system for Type-4 tank. The full nonlinear simulation programs with gun bending modes and nonlinearities were developed to estimate, analyze and design the driving and stabilization system, and validated through the comparisons between simulations and test results of the existing Type-1 tank. The prototype is designed, fabricated, tested and evaluated on the test range as well as in the laboratory and followed by development and operational tests. The performance test results on stationary and on-the-move conditions are turned out to be superior to those of the advanced tanks developed in foreign countries.

• International Journal of Aeronautical and Space Sciences
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• 제8권1호
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• pp.129-139
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• 2007

In this paper, attitude control laws for simultaneous pointing of multiple spacecrafts are considered under a formation flying scenario. The basic approach lies in adaptive feedback gains using relative attitude information or maneuver time approximation for coordinated attitude control. Each control law is targeted to balancing mean motion or to correcting system response to the slowest satellite. The control gain adaptation is constructed by two approaches. The first one is using variable damping gain to manipulate speed of a fast system response, and the second one uses alternate natural frequency of the system under control. The validity and stability of the proposed approaches are examined analytically and tested through numerical simulations.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
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• pp.304-307
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• 2004

Satellite orbit determination using angles only data from single ground station is carried out. The KOMPSAT-1 satellite mono-pulse angle tracking data from 9-meter S-band antenna at KARI site in Daejeon are used for the orbit determination. Various angle tracking arcs from one-day to five-day are processed and the orbit determination results are analyzed. Antenna pointing data are predicted based on the orbit determination results to check the possibility of re-acquisition and tracking of the satellite signal. Normal satellite mission operations including orbit determination, antenna prediction, satellite re-acquisition and automatic tracking from predicted antenna angle pointing data are concluded to be possible when three-day angle tracking data from single tracking station are used for the orbit determination.

• 대한인간공학회지
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• 제19권3호
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• pp.39-49
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• 2000

During human-computer interaction(HCI), people typically send inputs to computers through electromechanical pointing devices. Many applied studies have therefore evaluated cursor-positioning movements made with various pointing devices. Though there were so many studies about performance of various pointing devices, it was nearly impossible to compare device performance each other until the Fitts' law was applied. It does appear that Fitts' law may predict performance reasonably well for the one C-D gain level. But in varying C-D gain levels, Fitts' law could not predict movement time. This study investigated the effects of C-D gain in mouse movement time and suggested a revised Fitts' model including C-D gain as an independent variable. The revised Fitts' model may use to measure the performance of various devices in varying C-D gain levels.

• ETRI Journal
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• 제16권2호
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• pp.27-41
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• 1994

A new mathematical model to predict the beam pointing instability of a nonconservative two-body satellite system in spinning injection mode has been developed by using Newton-Euler and projection methods. Since the on-axis and null axis of the omni antenna with toroidal pattern beam form a right angle, wobbling of the antenna on-axis is measured by determining the Euler angles which represent the orientation of the satellite's spin axis. Because of the complexity of the system which is a time varying, nonstationary, nonlinear dynamical system, a numerical method is used for the analysis. Computer simulation results present the effects of the mass distribution and internal mass motion on the antenna beam pointing.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.353-354
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• 2007

This paper proposes the method which estimates the pointing region at the real world. This paper uses the technique to easily calibrate a camera of Z. Zhang. First, we calculate the projection matrix of each camera by the technique. Next, we estimate the location of the shoulder and the fingertip. Then we compute the pointing region in 3D real world by using projection matrix of each camera. Experiment result showed that the error between estimated point and the plane center point is less than 5cm.