• Journal of the Optical Society of Korea
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• 제13권2호
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• pp.193-200
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• 2009

A compact imaging spectrometer (COMIS) is currently under development for use in the STSAT3 microsatellite. COMIS images the Earth's surface and atmosphere with ground sampling distances of ${\sim}30m$ in the $18{\sim}62$ spectral bands ($4.0{\sim}1.05{\mu}m$) for the nadir looking at an altitude of 700 km. COMIS has an imaging telescope and an imaging spectrometer box into which three electronics PCBs are embedded. These are designed into a single assembly with dimensions of 35(L) $\times$ 20(W) $\times$ 12(H) $cm^3$ and a mass of 4.3 kg. Optomechanical design efforts are focused on manufacturing ease, alignment, assembly, testing and improved robustness in space environments. Finite element analysis demonstrates that COMIS will survive in launch and space environments and perform the system modulation transfer function (MTF) in excess of 0.29 at the Nyquist frequency of the CCD detector (38.5 lines-per-mm).

• 항공우주기술
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• 제6권2호
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• pp.73-78
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• 2007

현재 개발되고 있는 위성용 전자광학시스템의 설계 파라미터를 적용하여 알려진 식에 의해 위성의 운용고도와 자세변화에 따른 전자광학시스템의 GSD 및 라인레이트 변화관계를 살펴보았다. 그리고 고도변화에 따른 적용 가능한 라인레이트와 위성의 지상 스캔율의 차이에 의해 발생할 수 있는 성능변화 요소로서의 MTF에 대한 영향을 검토하였다. 즉 현재 개발이 진행되고 있는 카메라 전자부의 설계 파라미터를 적용하여 조정 가능한 라인레이트의 한계를 알아보고 이에 의한 성능감소 변화를 검토함으로써 현재 개발 진행되는 전자광학시스템의 카메라전자부의 설계요소에 대한 분석을 수행하였다.

• International Journal of Aeronautical and Space Sciences
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• 제16권3호
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• pp.463-474
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• 2015

Future Ground Control Stations (GCSs) for Unmanned Aerial Vehicles (UAVs) teleoperation targets better situational awareness by providing extra motion cues to stimulate the vestibular system. This paper proposes a new virtual environment for long range Unmanned Aerial Vehicle (UAV) control via Non-Line-of-Sight (NLoS) communications, which is based on motion platforms. It generates motion cues for the teleoperator for extra sensory stimulation to enhance the guidance performance. The proposed environment employs the distributed component simulation over GSM network as a simulation platform. GSM communications are utilized as a multi-hop communication network, which is similar to global satellite communications. It considers a UAV mathematical model and wind turbulence effects to simulate a realistic UAV dynamics. Moreover, the proposed virtual environment simulates a Multiple Axis Rotating Device (MARD) as Human Machine Interface (HMI) device to provide a complete delay analysis. The demonstrated measurements cover Graphical User Interface (GUI) capabilities, NLoS GSM communications delay, MARD performance, and different software workload. The proposed virtual environment succeeded to provide visual and vestibular feedbacks for teleoperators via GSM networks. The overall system performance is acceptable relative to other Line-of-Sight (LoS) systems, which promises a good potential for future long range, medium altitude UAV teleoperation researches.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.442-444
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• 2007

How to observe the atmosphere is a subject of atmospheric research. The meteorological satellites and the ground states are used to do observation. However, both ways do not satisfy the requirement of scientists, especially the profiles of atmosphere on the ocean and the data for global atmosphere. Radio occultation (RO) technique, which has been used in planet science, is a method to solve the problem. In RO technique, the low Earth orbit (LEO) satellite receives the two frequency signal of Global Positioning System (GPS) satellite. The excess phase of the signal is calculated to retrieve the profiles of atmosphere parameters. In moist troposphere, the fluctuations appear in the phase of the signal and open loop (OL) is used to resolve it. The quality of the GPS signal generally deteriorates as the altitude decreases. In the procedure, the SNR of the GPS signal is used as the criterion. However, the SNR decreases with fluctuation which makes it difficult to locate the data of poor quality. In this paper, the phase of the signal will be used as part of the criterion.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.576-579
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• 2007

Timber inventory is a good starting point for developing strategies to effectively manage the timberland. In the sale of timberland, pricing is mostly based on this inventory. For a small timberland, inventory by conventional ground survey could be possible. In the case of large and nationwide business transactions, swift and inexpensive inventory is worth to be considered as the conventional methods require more experienced man power, money and time. In the present study, it was aimed to identify the chronicle of timberland such as changes that has occurred owing to silvicultural activities and by other means using the historical aerial photography and satellite data. Historical aerial photos from National Aerial Photography Program (NAPP), National High Altitude Photography (NHAP), Survey Photography and Landsat satellite data were used. Orthophotos were constructed using the DOQQ and DEM from USGS. Simple photo interpretation technique was employed to classify the orthophoto and satellite data. The plantation area was classified into softwood, mixed and hardwood. The timber age and the corresponding acreage details and the changes were also estimated. The result of this study could be more useful to the timberland buyers to better understand the chronicle of timberland of their interest prior to transactions.

• 대기
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• 제26권2호
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• pp.289-299
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• 2016

Optical properties of aerosols associated with haze events over Seoul were examined using ground-based skyradiometer and satellite-borne CALIOP and MODIS measurements over the 2009~2010 period. It is shown that aerosol optical thickness (AOT), ${\AA}ngstr{\ddot{o}}m$ exponents (${\alpha}$), and fine-mode particles increase during the haze events. The CALIOP-measured vertical profiles of aerosol during the haze events revealed that most of aerosols are loaded within layers below 4 km altitude. A large portion of these events appear to be related to the long-range transport of aerosols from China; about 35% and 18% of the haze events observed over Seoul were traced back to northern China and southern China, respectively. Compared with optical properties for locally-induced haze events (25%), these long-range transported aerosols are found to have relatively higher AOTs.

• Journal of the Optical Society of Korea
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• 제18권5호
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• pp.605-610
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• 2014

Clouds play an important role in climate change, in the prediction of local weather, and also in aviation safety when instrument assisted flying is unavailable. Presently, various ground-based instruments used for the measurements of the cloud base height or velocity. Lidar techniques are powerful and have many applications in climate studies, including the clouds' temperature measurement, the aerosol particle properties, etc. Otherwise, it is very circumscribed in cloud velocity measurements because there is no Doppler effect if the clouds move in the perpendicular direction to the laser beam path of Doppler lidar. In this paper, we present a method for the measurement of cloud velocity using lidar's range detection and DIC (Digital Image Correlation) system to overcome the disadvantage of Doppler lidar. The lidar system acquires the distance to the cloud, and the cloud images are tracked using the developed fast correlation algorithm of DIC. We acquired the velocities of clouds using the calculated distance and DIC algorithm. The measurement values had a linear distribution.

• 한국위성정보통신학회논문지
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• 제2권1호
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• pp.21-26
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• 2007

탑재된 광학카메라 또는 영상레이더를 이용하여 지구관측 임무를 수행하는 저궤도 지구관측위성은 지상으로부터 수 백 km 고도의 궤도상에서 극심한 열하중을 받게 된다. 이로 인하여 구조체의 열변형이 발생하게 되고 결과적으로 구조체에 장착된 탑재체가 지상의 원하는 지점을 관측하지 못하는 문제점이 발생하게 된다. 이러한 열변형에 의한 탑재체의 지향방향의 변화를 열지향오차라고 한다. 열지향오차 해석은 열해석, 온도값 변환 및 구조해석의 세 단계로 수행된다. 본 논문에서는 열지향오차 해석을 통하여 위성의 임무수행 가능성을 기술하는것을 목적으로 하였다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.548-551
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• 2010

추력 150 lbf 급의 초소형 터보제트 엔진이 개발되었다. 본 엔진은 소형 무인항공기(UAV), 기만기, 대공망 제압용 유도무기 등 다양한 무기체계에 적용이 될 수 있도록 고성능, 소형, 저가로 설계되었으며, 시제엔진을 제작하여 지상 성능 시험 및 고도 시험을 수행하였다. 본 논문에서는 소형, 저가, 고효율 터보제트 엔진을 구성하는 각 엔진 구성품의 특징, 구조, 구성품 및 엔진 시험 결과 등에 대하여 기술하였다.

• 대한기계학회논문집B
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• 제33권2호
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• pp.107-115
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• 2009

A Computational study was carried out in order to investigate the aerodynamic characteristics of circular cylinder moving near the wavy wall at a low Reynolds number of 50. Lattice Boltzmann method was used to simulate the flow field and immersed boundary method was combined to represent the moving cylinder and wavy wall regardless of the constructed grid in the domain. The aerodynamics characteristics of the cylinder moving near the wavy wall were represented by the comparing the lifting coefficients with various altitudes (H/D) and wave length and amplitudes of wavy wall. It indicated that the twice of increasing-decreasing variations of lifting coefficient are obtained while the cylinder moves near the wavy wall. The first variation is obtained where the cylinder locates near the peak of the wavy wall. Another variation occurs when the distance to the wavy wall becomes longer after passing the peak. It was also classified that three different patterns of relation between the lifting and drag coefficient of the cylinder. However, the classification is limited to the case of the same order of altitude, amplitude and wave length of the wavy wall.