• 천문학논총
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• 제13권1호
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• pp.39-54
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• 1998

We have developed solar observational system in the department of Astronomy & Space Sciences of KyungHee University, in order to monitor solar activities and construct solar database for space weather forecasting at maximum of 23rd solar cycle, as well as an solar education and exercise for undergraduate students. Our solar observational system consists of the full disk monitoring system and the regional observation system for H a fine structure. Full disk monitoring system is made of an energy rejection filter, 16cm refractor, video CCD camera and monitor. Monitored data are recorded to VHS video tape and analog output of video CCD can be captured as digital images by the computer with video graphic card. Another system for regional observation of the sun is made of energy rejection filter, 21cm Schmidt-Cassegrain reflector, H a filter with 1.6A pass band width and $375\times242$ CCD camera. We can observe H a fine structure in active regions of solar disk and solar limb, by using this system. We have carried out intense solar observations for a test of our system. It is found that Quality of our H a image is as good as that of solar images provided by Space Environmental Center. In this paper, we introduce the basic characteristics of the KyungHee Solar Observation System and result of our solar observations. We hope that our data should be used for space weather forecasting with domestic data of RRL(Radio Research Laboratory) and SOFT(SOlar Flare Telescope).

• 천문학회보
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• 제36권2호
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• pp.90.2-90.2
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• 2011

At Kyoto University, a continuous solar full-disk observation in CaII K line had been done during 44 years of 1926 - 1969. The observation was done with a Askania spectroheliograph on daily base. The images were taken on photographic plates. We started a project to archive these image data into a digital database which will be open to the public for scientific researches. One of the scientific usage of the database is to study the long term variation of the solar chromospheres. Since the area of CaII K plage area is a measure of solar chromospheric heating, we can do comparative study of the sunspot cycle and the chromospheric heating cycle of the sun. Another interesting field of scientific utilization of the database is the long term variation of the heating of terrestrial upper atmosphere. As was shown by Yokoyama, Masuda and Sato (2005), the area of the CaII K plage is a good proxy measure of solar EUV irradiation onto the upper atmosphere of the earth. Thus the completion of our database will serve to supply a basic and long-span data for upper atmospheric heating issues by the cooperative study with the Inter-university Upper atmosphere Global Observation NETwork (IUGONET) developed in Japan.

• 항공우주기술
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• 제11권1호
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• pp.103-110
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• 2012

천리안 위성 임무 운영 관련하여, 전구(Full Disk: FD) 영상 및 2개의 인접 확장북반구(Extended Northern Hemisphere: ENH) 영상들에 대한 기상 관측 임무와 동서방향 위치유지(East West Station Keeping: EWSK) 기동 임무가 서로 충돌할 경우, EWSK의 시간 이동을 통해 큰 기상영상들의 손실을 줄일 수 있다. 이를 위해 FD 및 2개 ENH 영상의 기상관측임무를 피하는 EWSK 시간 이동에 대해 충돌 확률을 고려한 해석적 방법을 제시하여 이론적 고찰을 수행하였으며, 천리안위성 운영에도 시험적으로 적용하였다. 이론적 고찰 결과와 시험 운영 결과를 종합하여 기상영상 회피 EWSK 시간 이동이 천리안위성 연료 소모에 미치는 영향에 대한 연구 결과를 제시하였다. 본 연구 결과는 천리안 기상 임무 활용의 극대화에 기여할 수 있을 것으로 기대한다.

• 대한원격탐사학회지
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• 제26권2호
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• pp.277-285
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• 2010

세계 최초로 개발된 정지궤도 해색탑재체(GOCI-I, Geostationary Ocean Color Imager-I)이 2010년 6월에 발사될 예정이다. GOCI-I의 수명은 약 7년 이므로 위성개발 소요기간 약 6년을 고려하면 제2호 정지궤도 해색탑재체의 개발을 위한 임무 및 이용자 요구사양을 준비해야할 시점이 되었다. 제2호의 임무는 우선 1호의 임무를 승계하는 것이므로 제1호와 유사한 관측 임무를 갖지만 가장 큰 차이점은 장기 기후 변화에 대응한 지구규모적 관측에 있다. 그리고 기존의 Local 관측은 그 공간해상도의 성능을 더 향상시킨 $250m{\times}250m$로 하였고, 1호에 비하여 부족한 band 수를 보강하여 12 개로 하였다. 어장정보를 위한 야간 관측을 위한 Panchromatic band를 추가하였다. 동시에 한반도 주변 고정된 영역 관측기능을 구름이 없는 해역 혹은 special event area로 신축적으로 변경 시킬 수 있는 기능을 갖게 함으로써 위성자료의 활용도를 크게 높이었다. 위성 운용은 1호와 같은 일 8회 관측, 그리고 Global mode인 full disk 관측에서는 일 1-2회 정도 관측할 수 있도록 하였다. 그리고 본 연구에서는 지금까지 위성개발 추진방법의 문제점을 해소한 개선된 개발 추진 방안에 대하여서도 제시하였다. 그 외 제2호의 하드웨어적인 구조 및 디자인에 대하여서는 국내외 개발사와의 상호협의가 필요하다.

• 천문학회보
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• 제45권1호
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• pp.65.1-65.1
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• 2020

We present high-resolution, high-sensitivity continuum data of NGC 4522 observed at 3 cm (X-band) and 10 cm (S-band) in full polarization mode using the JVLA. This observation has 2 - 4 times better spatial resolution and 2 - 5 times better sensitivity compared to previous continuum observations. NGC 4522 is a Virgo spiral galaxy undergoing active ram pressure stripping. This galaxy is particularly well known for the CO emission detected outside its stellar disk, some of which coincides with the extraplanar HI gas and Halpha patches. The major goal of our JVLA observation is to leverage our understanding of the influence of the ram pressure on the general ISM field and multi-phase medium. By combining our new deep radio continuum data and previous observations, we will investigate how the B-field properties can be affected by the ram pressure, and what roles the B-field plays in the stripping process of the multi-phased ISM and in the star formation activity when the ram pressure is present.

• 천문학회보
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• 제36권2호
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• pp.87.1-87.1
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• 2011

Since early 90's, the solar X-ray telescopes such as Yohkoh SXT and Hinode XRT have observed coronal magnetic structures on the Sun's surface in the range of about $40'{\times}40'$ field-of-view (FOV) covering the full solar disk. Thus it has been stressed by the scientists that the optical structure of solar telescopes should be designed with care for improving the uniformity over a wide FOV. There would be, however, no unique solution in designing the optical system of a telescope for overcoming perfectly the problem of off-axis response variation. As a consequence, the correction of optical imperfectness of telescopes has become an important calibration step that should be performed beforehand when the observed images are to be used for photometric purposes. In particular, a special care should be taken when performing the temperature analysis with thin and thick filters for flaring activities observed at the periphery of the full FOV. From the analyses of both pre-launch calibration and in-flight observation data, the optical characteristics for describing the performance of solar X-ray telescopes, especially in view of their energy dependence, will be introduced and discussed in our presentation.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.112-115
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• 2005

Communication Ocean Meteorological Satellite (COMS) for the hybrid mission of meteorological observation, ocean monitoring, and telecommunication service is planned to be launched onto Geostationary Earth Orbit in 2008. The meteorological payload of COMS is an imager which will monitor meteorological phenomenon around the Korean peninsular intensively and of Asian-side full Earth disk periodically. The meteorological imager (MI) of COMS has 5 spectral channels, I visible channel with the resolution of I km at nadir and 4 infrared channels with the resolution of 4 km at nadir. The characteristics of the COMS MI are introduced in the view points of user requirements, hardware characteristics, and operation features.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 추계학술대회 논문집
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• pp.127-133
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• 2001

Photoelastic isochromatic fringes related to the difference of principal stresses have some bandwidth whose light intensities are not constant and unsymmetrical in experimental image. Hence it is difficult to measure fringe order accurately at a data point by visual observation. In this study, the method of fringe sharpening, which can extract sharpened lines from both full-and half-order fringes by digital image processing, is developed. To test the method, various simple photoelastic fringe patterns are simulated and their image are processed to yield sharpened lines. The method is than applied to general problem such as image of a circular disk compressed by concentrated loads and a cylinder subjected to internal pressure. The procedure is proved to be capable of extracting sharpened lines accurately from photoelastic isochromatic fringes.

• 한국정밀공학회지
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• 제10권3호
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• pp.220-230
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• 1993

Photoelastic isochromatic fringes related to the difference of principal stresses have some bandwidth whose light intensities are not constant and asymmetrical in experimental images. Hence, it is difficult to measure fringe order accurately at a data point by visual observation. In this study, a method of fringe sharpening, which can extract shapened lines from both full-and half-order fringes by digital image processing, is developed. To test the method, various simple photelastic fringe patterns are simulated and their images are processed to yield sharpened lines. The method is then applied to general problems such as images of a circular disk compressed by diametrically concentrated loads and a circular cylinder sybject to internal pressure. The procedure is proved to be capable of extracting sharpened lines accurately from photoelastic isochromatic fringes.

• Journal of Astronomy and Space Sciences
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• 제21권4호
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• pp.329-342
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• 2004

In this paper, we present preliminary feasibility studies on three types of solar observation payloads for future Korean Science and Technology Satellite (STSAT) programs. The three candidates are (1) an UV imaging telescope, (2) an UV spectrograph, and (3) an X-ray spectrometer. In the case of UV imaging telescope, the most important constraint seems to be the control stability of a satellite in order to obtain a reasonably good spatial resolution. Considering that the current pointing stability estimated from the data of the Far ultraviolet Imaging Spectrograph (FIMS) onboard the Korean STSAT-1, is around 1 arc minutes/sec, we think that it is hard to obtain a spatial resolution sufficient for scientific research by such an UV Imaging Telescope. For solar imaging missions, we realize that an image stabilization system, which is composed of a small guide telescope with limb sensor and a servo controller of secondary mirror, is quite essential for a very good pointing stability of about 0.1 arcsec. An UV spectrograph covering the solar full disk seems to be a good choice in that there is no risk due to poor pointing stability as well as that it can provide us with valuable UV spectral irradiance data valuable for studying their effects on the Earth's atmosphere and satellites. The heritage of the FIMS can be a great advantage of developing the UV spectrograph. Its main disadvantage is that two major missions are in operation or scheduled. Our preliminary investigations show that an X-ray spectrometer for the full disk Sun seems to be the best choice among the three candidates. The reasons are : (1) high temporal and spectral X-ray data are very essential for studying the acceleration process of energetic particles associated with solar flares, (2) we have a good heritage of X-ray detectors including a rocket-borne X-ray detector, (3) in the case of developing countries such as India and Czech, solar X-ray spectrometers were selected as their early stage satellite missions due to their poor pointing stabilities, and (4) there is no planned major mission after currently operating Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI) mission. Finally, we present a preliminary design of a solar X-ray spectrometer covering soft X-ray (2 keV) to gamma ray (10 MeV).