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정명재 ( Myeong Jae Jeong ) 대한원격탐사학회 2013 大韓遠隔探査學會誌 Vol.29 No.5
이 연구에서는 상용 디지털 카메라를 이용하여 야간에 촬영된 월면 영상을 분석하여 야간의 대기 광학두께와 에어로솔 광학두께를 추정하였다. 기본적으로 랑리회귀법을 이용하였으며 구름이 없고 대기의 광학적 특성이 비교적 안정한 날에 관측을 수행하였다. 카메라의 적색(R), 녹색(G), 청색(B) 채널의 파장별 반응함수를 이용하여 월광관측에 대한 유효 중심파장 및 레일리 광학두께를 추정하였으며, 랑리 회귀법에서 유도된대기광학두께로부터 레일리 광학두께를 제하여 에어로솔 광학 두께를 산출하였다. 야간에는 독립적인 방법으로 산출된 검증자료나 다른 에어로솔 광학두께 자료가 거의 없으므로 월면 관측이 이루어지기 수 시간 전의 주간에 정밀한 태양분광광도계로 측정된 에어로솔 광학두께 자료와 MODIS 위성센서 관측으로부터 산출된 에어로솔 광학두께 자료를 본 연구에서 월면 관측을 통해 산출된 자료와 비교하였다. 비교 결과 R, G, B 채널에서 대략 0.1정도의 오차 범위에서 월면 영상분석을 통해 에어로솔 광학두께의 추정이 가능함을 알 수 있었다. 단, 대기 중의 에어로솔 입자들의 크기를 나타내는 모수인 앙스트롬지수(Angstrom Exponent)는 파장별 광학두께의 작은 오차에도 큰 오차를 가질 수 있기 때문에 에어로솔 광학두께의 오차에 비해 비교적 큰 오차를 보일수 있음이 나타났다. 그럼에도 불구하고, 야간의 에어로솔 광학두께 자료가 많지 않은 현실에서 저비용으로 월면 관측을 통하여 에어로솔 광학두께를 산출할 수 있는 가능성을 찾았다는 점에서 본 연구의 의의가 있으며 앞으로 보다 많은 관측과 분석을 통해 보다 향상된 야간 에어로솔 광학두께 추정이 가능할 것으로 보인다. Atmospheric optical thickness during nighttime was estimated in this study using analysis on the images of the moon taken from commercial digital camera. Basically the Langely Regression method was applied to the observations of the moon for the cloudless and optically stable sky conditions. The spectral response functions for the red(R), green(G), and blue(B) channels were employed to derive effective wavelength centers of each channel for the observations of the moon, and the correspondent Rayleigh optical thickness were also calculated. Aerosol optical thickness (AOT) was calculated by subtracting Rayleigh optical thickness from the atmospheric optical thickness derived from the Langley regression method. As there are only handful of nighttime AOT observations, the AOT from the moon observations was compared with the AOT from sun-photometers and the MODIS satellite sensor, which was taken several hours before the moon observations of this study. As a result, the values of AOT from moon observations agree with those from sun-photometers and MODIS within 0.1 for the R, G, B channels of the digital camera. On the other hand, Angstrom Exponent seems to be subject to larger errors due to its sensitiveness to the spectral errors of AOT. Nevertheless, the results of this study indicate that the method reported in this study is promising as it can provide nighttime AOT relatively easily with a low cost instrument like digital camera. More observations and analyses are warranted to attain improved nighttime AOT observations in the future.
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안명환,김준,이규원,김상우 한국기상학회 2023 대기 Vol.33 No.2
Remote sensing becomes a new and core framework for the atmospheric sciences andclosely related areas concerning with the ever-changing global environmental status. However,remote sensing in the Korea Meteorological Society is relatively new, where the first relevantpaper is appeared in 1983, as well as is an area with relatively limited number of research groups. Here, we review and summarize some of the key progress in this area within Korea MeteorologicalSociety focusing on the areas of satellite, radar, and ground based remote sensing such aslidar, spectrometer and sun photometer. Overall, the area is shown to have the most significantprogress occur along with the acquisition of the key infra structures such as the COMS (Communication,Ocean and Meteorological Satellite) and S-band radar system led by Korea MeteorologicalAdministration in early 2000. After that, the area has quickly developed into a status playingimportant roles to lead and support the overall activities in the atmospheric measurements. It isexpected that the importance and role of the remote sensing will increase in the coming years.
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Depolarization Ratio Retrievals Using AERONET Sun Photometer Data
Kyung-Hwa Lee,Detlef Müller,노영민,신성균,Dong-Ho Shin 한국광학회 2010 Current Optics and Photonics Vol.14 No.3
We present linear particle depolarization ratios (LPDRs) retrieved from measurements with an AERONET Sun photometer at the Gwangju Institute of Science and Technology (GIST), Korea (35.10° N, 126.53° E) between 19 October and 3 November 2009. The Sun photometer data were classified into three categories according to Ångström exponent and size distribution: 1) pure Asian dust (19 October 2009), 2) Asian dust mixed with urban pollution observed in the period from 20-26 October 2009, and 3) clean conditions (3 November). We show that the LPDRs can be used to distinguish among Asian dust, mixed aerosol, and non-Asian dust in the atmosphere. The mean LPDR of the pure Asian dust case is 23 %. Mean LPDRs are 13 % for the mixed case. The lowest mean LPDR is 6 % in the clean case. We compare our results to vertically resolved LPDRs (at 532 nm) measured by a Raman LIDAR system at the same site. In most cases, we find good agreement between LPDRs derived with Sun photometer and measured by LIDAR.
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양희수,봉수찬,조경석,최성환,박종엽,김지헌,백지혜,나자경,Mingzhe Sun,Qian Gong 한국천문학회 2018 Journal of The Korean Astronomical Society Vol.51 No.2
In a solar coronagraph, the most important component is an occulter to block the direct light from the disk of the sun Because the intensity of the solar outer corona is $10^{-6}$ to $10^{-10}$ times of that of the solar disk (\ir), it is necessary to minimize scattering at the optical elements and diffraction at the occulter. Using a Fourier optic simulation and a stray light test, we investigated the performance of a compact coronagraph that uses an external truncated-cone occulter without an internal occulter and Lyot stop. In the simulation, the diffracted light was minimized to the order of $7.6\times10^{-10}$ \ir~when the cone angle $\theta_c$ was about $0.39\degree$. The performance of the cone occulter was then tested by experiment. The level of the diffracted light reached the order of $6\times10^{-9}$ \ir~at $\theta_c=0.40\degree$. This is sufficient to observe the outer corona without additional optical elements such as a Lyot stop or inner occulter. We also found the manufacturing tolerance of the cone angle to be $0.05\degree$, the lateral alignment tolerance was $45$\,\um, and the angular alignment tolerance was $0.043\degree$. Our results suggest that the physical size of coronagraphs can be shortened significantly by using a cone occulter.
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