• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.39.2-39.2
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• 2010

In this paper, I present the domestic development of near infrared camera systems for the ground telescope and the space satellite. These systems are the first infrared instruments made for astronomical observation in Korea. KASINICS (KASI Near Infrared Camera System) was developed to be installed on the 1.8m telescope of the Bohyunsan Optical Astronomy Observatory (BOAO) in Korea. KASINICS is equipped with a $512{\times}512$ InSb array enable L band observations as well as J, H, and Ks bands. The field-of-view of the array is $3.3'{\times}3.3'$ with a resolution of 0.39"/pixel. It employs an Offner relay optical system providing a cold stop to eliminate thermal background emission from the telescope structures. From the test observation, limiting magnitudes are J=17.6, H=17.5, Ks=16.1 and L(narrow)=10.0 mag at a signal-to-noise ratio of 10 in an integration time of 100 s. MIRIS (Multi-purpose InfraRed Imaging System) is the main payload of the STSAT-3 in Korea. MIRIS Space Observation Camera (SOC) covers the observation wavelength from $0.9{\mu}m$ to $2.0{\mu}m$ with a wide field of view $3.67^{\circ}{\times}3.67^{\circ}$. The PICNIC HgCdTe detector in a cold box is cooled down below 100K by a micro Stirling cooler of which cooling capacity is 220mW at 77K. MIRIS SOC adopts passive cooling technique to chill the telescope below 200K by pointing to the deep space (3K). The cooling mechanism employs a radiator, a Winston cone baffle, a thermal shield, MLI of 30 layers, and GFRP pipe support in the system. Opto-mechanical analysis was made in order to estimate and compensate possible stresses from the thermal contraction of mounting parts at cryogenic temperatures. Finite Element Analysis (FEA) of mechanical structure was also conducted to ensure safety and stability in launching environments and in orbit. MIRIS SOC will mainly perform the Galactic plane survey with narrow band filters (Pa $\alpha$ and Pa $\alpha$ continuum) and CIB (Cosmic Infrared Background) observation with wide band filters (I and H) driven by a cryogenic stepping motor.

• Korean Journal of Remote Sensing
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• v.26 no.2
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• pp.175-188
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• 2010

A new correction method is required for the Geostationary Ocean Color Imager (GOCI), which is the world's first ocean color observing sensor in geostationary orbit. In this paper we introduce a new method of atmospheric and the Bidirectional Reflectance Distribution Function(BRDF) correction for GOCI. The Spectral Shape Matching Method(SSMM) and the Sun Glint Correction Algorithm(SGCA) were developed for atmospheric correction, and BRDF correction was improved using Inherent Optical Property(IOP) data. Each method was applied to the Sea-Viewing Wide Field-of-view Sensor(SeaWiFS) images obtained in the Korean sea area. More accurate estimates of chlorophyll concentrations could be possible in the turbid coastal waters as well as areas severely affected by aerosols.

• Journal of Astronomy and Space Sciences
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• v.31 no.1
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• pp.83-90
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• 2014

The NISS onboard NEXTSat-1 is being developed by Korea astronomy and space science institute (KASI). For the study of the cosmic star formation history, the NISS performs the imaging spectroscopic observation in the near-infrared range for nearby galaxies, low background regions, star-forming regions and so on. It is designed to cover a wide field of view ($2{\times}2$ deg) and a wide wavelength range from 0.95 to $3.8{\mu}m$ by using linear variable filters. In order to reduce the thermal noise, the telescope and the infrared sensor are cooled down to 200 K and 80 K, respectively. Evading a stray light outside the field of view and making the most use of limited space, the NISS adopts the off-axis reflective optical system. The primary and the secondary mirrors, the opto-mechanical part and the mechanical structure are designed to be made of aluminum material. It reduces the degradation of optical performance due to a thermal variation. This paper presents the study on the conceptual design of the NISS.

• Proceedings of KOSOMES biannual meeting
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• 2003.11a
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• pp.191-193
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• 2003

Temporal and spatial variability of phytoplankton pigment concentrations around the Korea Peninsula was described, using the monthly mean composite images of the SeaWiFS (Sea-Viewing Wide Field-of-View Sensor). The high pigment concentrations appear in the spring and fall in the East Sea The spring bloom in the southern regions (in April) occurs one month in advance in comparison with tint in the northern regions (in May). In summer season, the pigment concentrations are low all over the region in the East Sea And the high pigment concentrations exist yearly around warm stream along the coast of the East Sea, and in the coast of the West Sea and South Sea In particular, the high pigment concentrations linking near the mouth q the Yangze River to coast of South Sea in Korea appear during August to December.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.39.2-39.2
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• 2017

Over the last decade, deep studies of nearby galaxies have led to the discovery of vast stellar envelopes that are often rich in substructure. These components are naturally predicted in models of hierarchical galaxy assembly, and their observed properties place important constraints on the amount, nature, and history of satellite accretion. One of the most effective ways of mapping the peripheral regions of galaxies is through resolved star studies. Using wide-field cameras equipped to 8 m class telescopes, it has recently become possible to extend these studies to systems beyond the Local Group. Located at a distance of 3.6 Mpc, M81 is a prime target for wide-field mapping of its resolved stellar content. In this talk, we present the detailed results from our deep wide-field imaging survey of the M81 group with the Hyper Suprime-Cam (HSC), on the Subaru Telescope. We report on the analysis of the structures, stellar populations, and metallicities of old dwarf galaxies such as NGC3077, IKN, KDG061, as well as young stellar systems such as Arp's Loop and Holmberg IX. Several candidates for yet-undiscovered faint dwarf galaxies and young stellar clumps in the M81 group will also be introduced. The peculiar galaxy NGC3077 has been classified as the irregular galaxy. Okamoto et al. (2015, ApJ 809, L1) discovered an extended halo structure with S-shape elongated tails, obvious feature of tidal interaction. With a help of numerical simulation by Penarrubia et al. (2009, ApJ 698, 222), we will demonstrate that this tidal feature was formed during the latest close encounters between M81, M82, and NGC 3077, which induced star formation in tidally stripped gas far from the main bodies of galaxies. It is not clear whether the latest tidal interaction was the first close encounters of three galaxies. If NGC3077 is still surrounded by the dark matter halo, it implies that NGC3077 has undergone the first tidal stripping by larger companions. Kinematic studies of inter galactic globular clusters and planetary nebulae would tell us the past history of tidal interaction in this group of galaxies.

• Journal of the Optical Society of Korea
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• v.17 no.2
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• pp.142-147
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• 2013

In order to deduce the difficulty of fixing the Ritchey-Chretien (R-C) dual reflective optical system and enhance the stability of the secondary mirror, a compact integral structure is presented here composed of two transmitting and two reflective aspheric surfaces. The four surfaces were manufactured from a single germanium lens and integrated together. The two reflective surfaces formed by coating the inner reflecting films were assembled in one lens. It makes the installation of the two mirrors easier and the structure of the secondary mirror more stable. A design of mid-wave infrared (MWIR) compact imaging system is presented with a spectral range chosen as $3.7-4.8{\mu}m$. The effective focal length is f=90 mm. The field of view (FOV) for the lens is $4.88^{\circ}$. It has good imaging capability with Modulation Transfer Function (MTF) of all field of view more than 0.55 close to the diffraction limitation. Outdoor experiments were carried out and it is shown that the integral catadioptric optical system performs well on imaging.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.64.1-64.1
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• 2013

The point spread function (PSF) of an optical system is in general defined as a two-dimensional intensity distribution which results from a single point source at infinity. It is an important key for the evaluation of the optical performance of an astronomical telescope. The PSFs of the soft X-ray telescope (SXT) aboard Yohkoh were measured in a wide range of the field-of-view under the in-flight configuration at White Sands Missile Range prior to launching the satellite. It has been known that the SXT PSF has a sharp peak at the core and the intensity drops very fast as it goes distant from the center. Due to the combination of this sharp peak at the PSF core and the effect of undersampling by a large pixel size, a carefully designed method is requested in the examination of the PSF data. The pattern of the SXT PSF is determined by the fitting of a mathematical functional form to the pre-launch experimental data. The elliptical Moffat function has been adopted for the evaluation of the SXT PSF. It is revealed from our study that the SXT PSF shows a peculiar characteristics, and thus a careful consideration on the undersampling effect and also a proper choice of statistics are necessary for the determination of the best fit function of the PSF. Details on the on- and off-axis SXT PSF in the field-of-view will be introduced and discussed in our presentation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.10
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• pp.2464-2478
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• 2013

Image stitching techniques produce an image with a wide field-of-view by aligning multiple images with a narrow field-of-view. While conventional algorithms successfully stitch images with a small parallax, structure misalignment may occur when input images contain a large parallax. This paper presents an image stitching algorithm that aligns images with a large parallax by regional linear warping. To this end, input images are first approximated as multiple planar surfaces, and different linear warping is applied to each planar surface. For approximating input images as multiple planar surfaces, the concept of dominant edges is introduced. Dominant edges are defined as conspicuous edges of lines in input images, and extracted dominant edges identify the boundaries of each planar surface. Dominant edge extraction is conducted by detecting distinct changes of local characteristics around strong edge pixels. Experimental results show that the proposed algorithm successfully stitches images with a large parallax without structure misalignment.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.5 s.305
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• pp.79-84
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• 2005

In this paper, we developed an omni-directional surveillance and motion detection method. The fish-eye lens provides a wide field of view image. Using this image, the equi-distance model for the fish-eye lens is applied to get the perspective and panorama images. Generally, we must consider the trade-off between resolution and field of view of an image from a camera. To enhance the resolution of the result images, some kind of interpolation methods are applied. Also the moving edge method is used to detect moving objects for the object tracking.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.78.1-78.1
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• 2017

We present a noble method to determine BH mass of many AGNs directly through reverberation mapping using a small telescope with wide-field of view. In 2017 August we installed five medium-band filters to a 0.25m diameter $5deg^2$ FOV telescope at the McDonald observatory. The width of these filters (FWHM ~ 50nm) are matched to the broad line width of type-1 AGNs at various redshifts. From recently obtained data, about r ~ 19 magnitude AGNs can be detected in line component with 150s exposure. With this magnitude limit, about 20~30 AGNs can be studied in one field. We plan to carry out at one day cadence observation over 20~30 fields, enabling us to monitor up to ~1000 AGNs over a wide range of variability. This poster presents out plan and early results from test observation.