• Publications of The Korean Astronomical Society
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• v.19 no.1
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• pp.129-133
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• 2004

In the past, radio astronomers have sought isolation from man-made signals by placing their telescopes in remote locations. These measures may no longer safeguard scientific observations, since NGSO satellite systems, particularly low-Earth orbit (LEO) systems, are usually designed to provide global or wide regional coverage. Further, radio astronomers have historically made their observations in the frequency bands allocated for their use by the member countries of the International Telecommunication Union (ITU). The science of radio astronomy could be adversely impacted by the deployment of large constellations of new non-geostationary orbiting (NGSO) satellites for telecommunications, navigation and Earth observation, and the proliferation of new, high-power broadcasting and telecommunication satellites in geostationary (GSO) orbits. Radio telescopes are extremely sensitive, and, in certain situations, signals from satellites can overwhelm the signals from astronomical sources. This paper describes the problem in detail and identifies ways to mitigate it without adversely affecting the continued vigorous growth of commercial space-based telecommunications.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.57.2-57.2
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• 2017

Remote and robotic telescopes are the most effective instrument for astronomical survey projects. The system is based on the dynamic operation of all astronomical instruments such as dome and telescope control system (TCS), focuser, filter wheel and data taking camera. We adopt the ASCOM driver platform to control the instruments through the integrated software. It can convert different interface libraries from various manufacturers into a uniform standard library. This allows us to effectively control astronomical instruments without modifying codes. We suggest a conceptual design of software for automation of a small telescope such as the new wide-field 0.25m telescope at McDonald Observatory. It can also be applied to operation of multi-telescopes in future projects.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.32.2-32.2
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• 2017

Stars form in dense core within the molecular clouds. The prestellar cores provide information of the physical characteristics at the very early stages of star formation. The low dust temperature (<14K) of Planck cold clumps/cores (PGCCs) make them likely to be prestellar objects or at the very initial stage of protostellar collapse. We have been conducting the legacy surveys of Planck cold clumps with the JCMT, the TRAO 14-m and many other telescopes. We aim to study of the initial conditions of star formation and chemical evolutions of the cores in the different environments. From JCMT SCUBA-2 $850{\mu}m$ survey (SCOPE), we have already identified hundreds of dense cores, which may be at the earliest phase of star formation. Therefore in order to explore the chemical evolution of these dense cores, we used KVN telescopes in order to observe 75 well selected SCUBA-2 cores in many molecules as the follow-up project of KVN Pilot Observation of SCUBA-2. These observations will help advance our understanding of the propoerties of these SCUBA-2 cores in PGCCs.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.1
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• pp.72.2-72.2
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• 2013

An off-axis telescope has several advantages in optical performance comparing with a conventional on-axis telescope. However, in general, an off-axis telescope has a narrow field of view due to the linear astigmatism caused by the asymmetric structure. It was shown in the previous work that the linear astigmatism can be eliminated by properly configuring parameters in a confocal off-axis reflector system. Furthermore, the third order aberrations of a confocal off-axis telescope can be minimized by optimizing the shape of the mirrors. Despite many advantages, the confocal off-axis telescopes have been evaded because of difficulties of off-axis mirror fabrication, alignment process and unaccustomed off-axis baffle design. The baffle for the off-axis telescope should be designed considering that the effects of stray lights are different because of the asymmetry of off-axis system. In this poster, the design, manufacturing, and test for the baffle and housing of an off-axis telescope are presented.

• Journal of The Korean Astronomical Society
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• v.45 no.1
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• pp.7-17
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• 2012

Y-band is a broad passband that is centered at ~1 ${\mu}m$. It is becoming a new, popular window for extragalactic study especially for observations of red objects thanks to recent CCD technology developments. In order to better understand the general characteristics of objects in Y-band, and to investigate the promise of Y-band observations with small telescopes, we carried out imaging observations of several extragalactic fields, brown dwarfs, and high redshift quasars with Y-band filter at the Mt. Lemmon Optical Astronomy Observatory and the Maidanak observatory. From our observations, we constrain the bright end of the galaxy and the stellar number counts in Y-band. We also test the usefulness of high redshift quasar (z >6) selection via i - z - Y color-color diagram, to demonstrate that the i - z - Y color-color diagram is effective for the selection of high redshift quasars even with a conventional optical CCD camera installed at a 1-m class telescope.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.61.3-62
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• 2016

An asteroid family is a group of asteroidal objects in the proper orbital element space (a, e, and i), considered to have been produced by a disruption of a large parent body through a catastrophic collision. Family members usually have similar surface properties such as spectral taxonomy types, colors, and visible geometric albedo with a same dynamical age. Therefore an asteroid family could be called as a natural Solar System laboratory and is also regarded as a powerful tool to investigate space weathering and non-gravitational phenomena such as the Yarkovsky/YORP effects. We carry out time series photometric observations for a number of asteroid families to obtain their physical properties, including sizes, shapes, rotational periods, spin axes, colors, and H-G parameters based on nearly round-the-clock observations, using several 0.5-2 meter class telescopes in the Northern hemisphere, including BOAO 1.8 m, LOAO 1.0 m, SOAO 0.6 m facilities in KASI, McDonald Observatory 2.1 m instrument, NARIT 2.4 m and TUG 1.0 m telescopes. This study is expected to find, for the first time, some important clues on the collisional history in our Solar System and the mechanisms where the family members are being transported from the resonance regions in the Main-belt to the near Earth space.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.241-241
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• 2012

MOGABA is a project monitoring of gamma-ray bright AGN(Active Galactic Nuclei). Since May 2011, we have observed total flux, degree of linear polarization, and polarization angle of about twenty AGN once a week at 22, 43 and 86GHz using KVN(Korean VLBI Network) 21m radio telescopes. We have observed variation of total flux of BLLAC and OJ287 from May 2011 to March 2012. We have observed flares of total flux at 22GHz for those sources from October 2011 to November 2011. In this paper we report the variation of total flux, degree of linear polarization and polarization angle at 22, 43, 86GHz for BLLAC and OJ287.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.239.2-239.2
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• 2012

We report preliminary results of MOGABA project for monitoring total flux density, linearly polarized flux, and polarization angle at 22, 43 and 86GHz of Gamma-ray bright AGN (Active Galactic Nuclei) with KVN (Korean VLBI Network) 21-m radio telescopes. The project has been conducted in one year since May 2011 with an effective monitoring cycle of 1 week, observing four main objects (3C 454.3, BL Lac, 3C 273, and 3C 279). More objects were included in the source list when they had flared in Gamma-ray. Especially, we included a compact radio source at the Galactic center, SgrA* since Jan. 2012. In this paper, we report the current status of the project and preliminary results for the monitoring observations.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.221.1-221.1
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• 2012

The Korea Astronomy and Space Science Institute (KASI) is developing three 1.6m optical telescopes with $18k{\times}18k$ mosaic CCD cameras. These telescopes will be installed and operated at Chile, South Africa, and Australia for Korea Micro-lensing Telescope Network (KMTNet) project. The main scientific goal of the project is to discover earth-like extra-solar planets using the gravitational micro-lensing technique. To achieve the goal, each telescope at three sites will continuously monitor the specific region of Galactic bulge with 2.5 minute cadence for five years. Assuming 12 hour observation in maximum for a night, the amount of 200 GB file storage is required for one night observation at one observatory. If we consider the whole project period and the data processing procedure, a few PB class data storage, high-speed network, and high performance computers are essential. In this presentation, we introduce the KMTNet data management plan that handles gigantic data; raw image collecting, image processing, photometry pipeline, database archiving, and backup.

• Journal of Appropriate Technology
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• v.5 no.2
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• pp.114-117
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• 2019

Ethiopia becomes a leading country in Africa as she possesses two 1 m telescopes which are unique in East Africa. Building the telescopes evoked people's interest on Astronomy and Space, and the passion is continued to space development and founding a large telescope. Ethiopia Space Science and Technology Institute was established, Adama Science and Technology University and other universities get in education and research & development (ERD). In this paper, status of Astronomy and Space science in Ethiopia is reviewed and collaboration prospect is studied.