• 제목/요약/키워드: Optical Observation

검색결과 756건 처리시간 0.031초

Minimum Number of Observation Points for LEO Satellite Orbit Estimation by OWL Network

  • Park, Maru;Jo, Jung Hyun;Cho, Sungki;Choi, Jin;Kim, Chun-Hwey;Park, Jang-Hyun;Yim, Hong-Suh;Choi, Young-Jun;Moon, Hong-Kyu;Bae, Young-Ho;Park, Sun-Youp;Kim, Ji-Hye;Roh, Dong-Goo;Jang, Hyun-Jung;Park, Young-Sik;Jeong, Min-Ji
    • Journal of Astronomy and Space Sciences
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    • 제32권4호
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    • pp.357-366
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    • 2015
  • By using the Optical Wide-field Patrol (OWL) network developed by the Korea Astronomy and Space Science Institute (KASI) we generated the right ascension and declination angle data from optical observation of Low Earth Orbit (LEO) satellites. We performed an analysis to verify the optimum number of observations needed per arc for successful estimation of orbit. The currently functioning OWL observatories are located in Daejeon (South Korea), Songino (Mongolia), and Oukaïmeden (Morocco). The Daejeon Observatory is functioning as a test bed. In this study, the observed targets were Gravity Probe B, COSMOS 1455, COSMOS 1726, COSMOS 2428, SEASAT 1, ATV-5, and CryoSat-2 (all in LEO). These satellites were observed from the test bed and the Songino Observatory of the OWL network during 21 nights in 2014 and 2015. After we estimated the orbit from systematically selected sets of observation points (20, 50, 100, and 150) for each pass, we compared the difference between the orbit estimates for each case, and the Two Line Element set (TLE) from the Joint Space Operation Center (JSpOC). Then, we determined the average of the difference and selected the optimal observation points by comparing the average values.

AERONET 선포토미터 데이터를 이용한 동북아시아 지역 대기 에어로졸 종류별 광학적 농도 변화 특성 연구 (A Study on the Variation of Aerosol Optical Depth according to Aerosol Types in Northeast Asia using Aeronet Sun/Sky Radiometer Data)

  • 노영민
    • 한국대기환경학회지
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    • 제34권5호
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    • pp.668-676
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    • 2018
  • This study has developed a technique to divide the aerosol optical depth of the entire aerosol (${\tau}_{total}$) into the dust optical depth (${\tau}_D$) and the pollution particle optical depth (${\tau}_P$) using the AERONET sun/sky radiometer data provided in Version 3. This method was applied to the analysis of AERONET data observed from 2006 to 2016 in Beijing, China, Seoul and Gosan, Korea and Osaka, Japan and the aerosol optical depth trends of different types of atmospheric aerosols in Northeast Asia were analyzed. The annual variation of ${\tau}_{total}$ showed a tendency to decrease except for Seoul where observation data were limited. However, ${\tau}_D$ tended to decrease when ${\tau}_{total}$ were separated as ${\tau}_D$ and ${\tau}_P$, but ${\tau}_P$ tended to increase except for Osaka. This is because the concentration of airborne aerosols, represented by Asian dust in Northeast Asia, is decreased in both mass concentration and optical concentration. However, even though the mass concentration of pollution particles generated by human activity tends to decrease, Which means that the optical concentration represented as aerosol optical depth is increasing in Northeast Asia.

Modelling of Aerosol Vertical Distribution during a Spring Season at Gwangju, Korea

  • Shin, Sung-Kyun;Lee, Kwon-Ho
    • Asian Journal of Atmospheric Environment
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    • 제10권1호
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    • pp.13-21
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    • 2016
  • The vertical distributions of aerosol extinction coefficient were estimated using the scaling height retrieved at Gwangju, Korea ($35.23^{\circ}N$, $126.84^{\circ}E$) during a spring season (March to May) of 2009. The aerosol scaling heights were calculated on a basis of the aerosol optical depth (AOD) and the surface visibilities. During the observation period, the scaling heights varied between 3.55 km and 0.39 km. The retrieved vertical profiles of extinction coefficient from these scaling heights were compared with extinction profile derived from the Light Detection and Ranging (LIDAR) observation. The retrieve vertical profiles of aerosol extinction coefficient were categorized into three classes according to the values of AODs and the surface visibilities: (Case I) the AODs and the surface visibilities are measured as both high, (Case II) the AODs and the surface visibilities are both lower, and (Others) the others. The averaged scaling heights for the three cases were $3.09{\pm}0.46km$, $0.82{\pm}0.27km$, and $1.46{\pm}0.57km$, respectively. For Case I, differences between the vertical profile retrieved from the scaling height and the LIDAR observation was highest. Because aerosols in Case I are considered as dust-dominant, uplifted dust above planetary boundary layer (PBL) was influenced this discrepancy. However, for the Case II and other cases, the modelled vertical aerosol extinction profiles from the scaling heights are in good agreement with the results from the LIDAR observation. Although limitation in the current modelling of vertical structure of aerosols exists for aerosol layers above PBL, the results are promising to assess aerosol profile without high-cost instruments.

Lidar Measurement of Optical Properties of Cirrus Clouds at Kwangju, Korea

  • Noh, Y.M.;Choi, S.C.;Kim, Y.J.
    • 대한원격탐사학회:학술대회논문집
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    • 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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    • pp.959-961
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    • 2003
  • Cirrus clouds observation was conducted using a lidar system in order to measure their height, thickness and optical depth at Kwangju (35$^{\circ}$10'N, 126$^{\circ}$53'), Korea in winter, December 2002, and spring March and April 2003. Cirrus clouds at high altitude can be distinguished from atmospheric aerosols location by high depolarization ratio and high altitude. Cirrus clouds were observed at 5${\sim}$12km altitudes with a high depolarization ratio from 0.2 to 0.5. Optical depth of cirrus clouds had varied from 0.28 to 1.81. Radiative effect of observed cirrus cloud on climate system was estimated to be negative net flux from ?0.24 to ?31.04 W/m$^{2}$.

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Physical Characteristics of Small Space Objects at High Orbits Based on Optical Methods

  • El-Hameed, Afaf M. Abd;Attia, Gamal F.;Abdel-Aziz, Yehia
    • Journal of Astronomy and Space Sciences
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    • 제34권1호
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    • pp.31-35
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    • 2017
  • Optical observation is one of the most common techniques used for characterizing the physical properties of unknown objects and debris in space. This research presents measurements and properties of the new object 96019 from ground-based optical methods. Optical observations of this small object were performed using a charge-coupled device (CCD) camera and the Santel-500 telescope at the Zvenigorod Observatory. The orbital elements and physical properties of this object, such as area-to-mass ratio, have been determined. The results show that this small object has a low area-to-mass ratio, between 0.009 and $0.12m^2/kg$. The light curve of object 96019 is given: Over the time intervals, variations in brightness are analyzed and the maximum brightness was found to be 12.4 magnitudes. The observational results show that, this object brightens by about three magnitudes over a time span of three minutes. Based on these observations, the characteristics and physical properties of this object are discussed.

보현산천문대 1.8m 망원경 돔의 방풍막 설치 (WINDSCREEN INSTALLED AT THE BOAO 1.8M TELESCOPE DOME)

  • 김승리;성현철;육인수;노진형
    • 천문학논총
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    • 제13권1호
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    • pp.65-73
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    • 1998
  • We installed windscreen at the BOAO 1.8m telescope dome, in order to reduce the degradation of image Quality under strong wind larger than 8m/sec. The windscreen was designed on the basis of that installed at the MSSSO 2.3m telescope dome in Australia. We developed control system (remote control and user program) of the windscreen, being able to operate the windscreen at observation room. We tested the performance of the windscreen under strong wind of 6-15m/see. Tracking error of the telescope, especially in altitude-axis, was greatly decreased when the windscreen was used. Standard deviation of the error was estimated to be less than 0.3arcsec, which has little effect on image quality.

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Observation of the Electromagnetically Induced Transparency and Dispersion-like Structure in Trapped Cs Atoms

  • Kim, Kyoung-Dae;Kwon, Mi-Rang;Kim, Jung-Bog;Moon, Han-Seb
    • Journal of the Optical Society of Korea
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    • 제5권4호
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    • pp.131-135
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    • 2001
  • We report experiemtnal results demonstrating the electromagnetically induced transparency (EIT) in trapped Cs atoms. EIT occurs at the Λ-type configuration where the re0-pumping laser simultaneously plays a role as the coupling laser in the presence of a magneto-optical trapping and weak magnetic fields. Dependences of EIT signal on both the intensity and the detuning of the coupling laser were investigated. Linear absorption spectra for cold cesium atoms in the magneto-optical trap have been observed and shown the pronounced dispersion-like structure with sub-natural linewidth of 1 MHz due to the cooling laser.

An Algorithm for the Characterization of Surface Crack by Use of Dipole Model and Magneto-Optical Non-Destructive Inspection System

  • Lee, Jin-Yi;Lyu, Sung-Ki;Nam, Young-Hyun
    • Journal of Mechanical Science and Technology
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    • 제14권10호
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    • pp.1072-1080
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    • 2000
  • Leakage magnetic flux (LMF) is widely used for non-contact detection of cracks. The combination of optics and LMF offers advantages such as real time inspection, elimination of electrical noise, high spatial resolution, etc. This paper describes a new nondestructive evaluation method based on an original magneto-optical inspection system, which uses a magneto-optical sensor, LMF, and an improved magnetization method. The improved magnetization method has the following characteristics: high observation sensitivity, independence of the crack orientation, and precise transcription of the geometry of a complex crack. The use of vertical magnetization enables the visualization of the length and width of a crack. The inspection system provides the images of the crack, and shows a possibility for the computation of its depth.

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평판 투명 물체의 형상측정을 위한 비접촉식 광센서 개발 (Development of a noncontact optical sensor for measuring the shape of transparent plates)

  • 윤상필;유영기
    • 제어로봇시스템학회:학술대회논문집
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    • 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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    • pp.214-214
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    • 2000
  • This paper deals with the non contact optical sensor to measure the shape of transparent plates such as glass panel of LCD(Liquid Crystal Display). The conventional methods to obtain the shape or thickness of a transparent plates are contact type sensor such as LVOT(Linear Variable Differential Transformer). Due to the contact between the tip of the sensor and the surface of objects, the tip is abraded. In addition, the high temperature glass casting makes the size of sensor body changed. These reasons makes the sensor degraded. In this paper, to overcome these problem, we proposed a low cost noncontact optical sensor this is composed of the Hologram laser unit of a CD-Pickup and a plastic lens. To evaluate the performance of the proposed optical sensor, a series of experiments were performed for various measurement condition. Based upon observation of the experimental result, the developed sensor shows good result for measuring the shape of transparent plates.

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GaAs 다중 양자 우물 구조에서 공명 여기된 엑시톤들에 의한 광학적 비선형성의 연구 (Optical Nonlinear Effects of Resonantly Excited Excitons on Excitons in GaAs Multiple Quantum Wells)

  • Park, Moongoo;Je, Koo-Chul;Park, Seung-Han
    • 한국광학회:학술대회논문집
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    • 한국광학회 2001년도 제12회 정기총회 및 01년도 동계학술발표회
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    • pp.50-51
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    • 2001
  • We investigate the effect of resonantly excited excitons on the optical-absorption of the n=1hh and n=2hh exciton resonances in GaAs quantum wells. Under quasistationary excitation condition using the pump and probe beam at tow temperature, we report the first observation of long range Coulomb screening by two dimensional exciton-exciton interaction, and discriminate unambiguously exciton bleaching between by long range Coulomb screening and the Pauli exclusion principle. (omitted)

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