• Journal of Navigation and Port Research
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• v.28 no.8
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• pp.653-657
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• 2004

The authors aim to design further an upgraded and self-contained position fixing system to meet the future commercial requirements. As a first step this paper is to investigate the theoretical structure of position fixing based on the nature of free gyro, in which the tilt angles of the two spin axes at an arbitrary position are measured respectively and the elapsed time with respect to a reference position or starting point is observed And it illustrates some limitations to be expected in this system.

• Journal of Astronomy and Space Sciences
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• v.22 no.4
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• pp.527-536
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• 2005

The perturbations caused by the Sun and the Moon are predominantly out-of-plane effects causing a change in the inclination and in the right ascension of ascending node of a geostationary satellite. Due to the change of the inclination, subsatellite latitude of the geostationary satellite has a daily variations of the same magnitude of the inclination. Therefore we need a facility to control the orbital inclination and right ascension of ascending node for maintaining the satellite position in specified subsatellite latitude boundary using thrusters. In this paper we studied North-South station keeping strategies of the COMS-1 such as Track-Back Chord Target (TBCT) method, Maximum Compensation Target (MCT) method and Minimum Fuel Target (MFT) method. We accomplished those North-South station keeping maneuvers for one year starting from December 2008. The required velocity increments to maintain the satellite are estimated as MCT 52.6065m/s, TBCT 52.2383m/s, MFT 51.5428m/s, respectively. We demonstrated that TBCT and MFT methods are proper to North-South station keeping for COMS-1. MFT method showed the minimum required velocity increments whereas TBCT traced narrow inclination boundary area for North-South station keeping.

• Journal of the Korean earth science society
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• v.28 no.4
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• pp.431-444
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• 2007

An automatic system of 36 cm telescope for the Web Based astronomy education was developed. The tracking accuracy of this system was about 1"/min. The pointing accuracy was ${\pm}10"$ in the right ascension direction, ${\pm}20"$ in the declination direction. These results will be improved continuously. The results of IRAF image analysis for the pilot observation data were stable, which means that this remote astronomical observation system is suitable f3r the education of astronomical observation.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.60.2-60.2
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• 2018

We present the near infrared JHK photometric properties and the spatial distribution of red supergiants(RSGs) of NGC 3623, NGC 3627 and NGC 3628 in the Leo Triplet system using the data obtained with 3.8m UKIRT(United Kingdom Infra-Red Telescope) at Hawaii. We checked interaction between the three galaxies by making a spatial density map of RSGs. From (J-K,K)0 Color-Magnitude Diagram which include resolved stars in three galaxy and control field with PARSEC isochrone, we figured out the RSG candidates of the Leo triplet are at 0.9<(J-K)0<1.2, mK<17.5 and separated them from background and foreground sources. Using gaussian kernel density estimation, we drew spatial density map of RSGs in the Leo triplet with an assumption that all RSGs are an identical population. The density map shows extended features of NGC 3628 to NGC 3627 along the declination direction. The asymmetries between NGC 3627 and NGC 3628 might be evidence for that the distribution of actual star components(RSGs) follows the neutral hydrogen distribution and also for interaction between two galaxies. And the extended features along the right ascension direction might be a supporting evidence for the existence of a TDG(Tidal Dwarf Galaxy). In case of NGC 3623, we could not see any sign of interaction in density map.

• Journal of Astronomy and Space Sciences
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• v.19 no.3
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• pp.231-242
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• 2002

So-ganui, namely small simplified armillary sphere, was invented as an astronomical instrument by Lee Cheon, Jeong Cho, Jung In-Ji under 16 years’ rule of King Sejong. We collect records and observed data on So-ganui. It is designed to measure position of celestial sphere and to determine time. It also can be transformed equatorial to horizontal, and horizontal to equatorial coordinate. It can measure the right ascension, declination, altitude and azimuth. It is composed of Sayu-hwan (Four displacements), Jeokdo-hwan (Equato.ial dial), Baekgak-hwan (Ring with one hundred-interval quarters), Gyuhyeong (Sighting aliadade), Yongju (Dragon-pillar) and Bu (Stand). So-ganui was used conveniently portable surveying as well as astronomical instrument and possible to determine time during day and night.

• Bulletin of the Korean Space Science Society
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• 2004.10b
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• pp.251-253
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• 2004

Automated east/west and north/south station-keeping maneuvers were simulated for the geostationary COMS (Communication, Ocean and Meteorological Satellite) satellite that will be launched around year 2008, The satellite has to be maintained within ${\pm}0.05^{\circ}$ at the nominal longitude of $128.2^{\circ}\;E$. The general perturbation method was used to keep the position of the geostationary satellite. Weekly based east/west and biweekly based north/south station-keeping maneuvers were investigated. The sun pointing perigee control method and two-bum strategy were used for the east/west station-keeping maneuver. Switching the right ascension of the ascending node to descending node was adopted for the north/south station-keeping maneuver. One year station-keeping maneuver was demonstrated and various station-keeping orbital parameters were analyzed.

• Journal of Astronomy and Space Sciences
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• v.38 no.2
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• pp.145-155
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• 2021

In this work, preliminary launch opportunities from NARO Space Center to the Sun-Earth Lagrange point are analyzed. Among five different Sun-Earth Lagrange points, L1 and L2 points are selected as suitable candidates for, respectively, solar and astrophysics missions. With high fidelity dynamics models, the L1 and L2 point targeting problem is formulated regarding the location of NARO Space Center and relevant Target Interface Point (TIP) for each different launch date is derived including launch injection energy per unit mass (C3), Right ascension of the injection orbit Apoapsis Vector (RAV) and Declination of the injection orbit Apoapsis Vector (DAV). Potential launch periods to achieve L1 and L2 transfer trajectory are also investigated regarding coasting characteristics from NARO Space Center. The magnitude of the Lagrange Orbit Insertion (LOI) burn, as well as the Orbit Maintenance (OM) maneuver to maintain more than one year of mission orbit around the Lagrange points, is also derived as an example. Even the current work has been made under many assumptions as there are no specific mission goals currently defined yet, so results from the current work could be a good starting point to extend diversities of future Korean deep-space missions.

• Journal of Astronomy and Space Sciences
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• v.40 no.3
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• pp.123-129
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• 2023

This paper presents an analysis of the trans-lunar trajectory insertion performance of the Korea Pathfinder Lunar Orbiter (KPLO), the first lunar exploration spacecraft of the Republic of Korea. The successful launch conducted on August 4, 2022 (UTC), utilized the SpaceX Falcon 9 rocket from Cape Canaveral Space Force Station. The trans-lunar trajectory insertion performance plays a crucial role in ensuring the overall mission success by directly influencing the spacecraft's onboard fuel consumption. Following separation from the launch vehicle (LV), a comprehensive analysis of the trajectory insertion performance was performed by the KPLO flight dynamics (FD) team. Both orbit parameter message (OPM) and orbit determination (OD) solutions were employed using deep space network (DSN) tracking measurements. As a result, the KPLO was accurately inserted into the ballistic lunar transfer (BLT) trajectory, satisfying all separation requirements at the target interface point (TIP), including launch injection energy per unit mass (C3), right ascension of the injection orbit apoapsis vector (RAV), and declination of the injection orbit apoapsis vector (DAV). The precise BLT trajectory insertion facilitated the smoother operation of the KPLO's remainder mission phase and enabled the utilization of reserved fuel, consequently significantly enhancing the possibilities of an extended mission.

• Journal of Korean Medical Ki-Gong Academy
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• v.11 no.1
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• pp.173-197
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• 2009

1. The concept about Jeok-chwiui(積聚) has been around since before "Hwangje-Naegyeong". Since "Hwangje-Naegyeong(黃帝內經)", Sik-jeok(食積) was made mention of specifically. In "Yu-gyeong(類經)", it is said that Sik-jeok is a combination of our body fluid and blood by bad eating and sleeping habits. 2. In the narrow sense Sik-jeok is indigestion and broadly it is inappropriately stagnant fluids in our body. 3. If studying on Sik-jeok in Dong-ui-bo-gam 1) It is located on the right side, in the epigastric region and between the skin and fascia. 2) The cause of Sik-jeok is indigestion, inappropriate temperature and weak stomach. 3) Symptoms of Sik-jeok are very diverse such as sick ascension, nausea, abdominal pain, headache, fever, etc. The right pulse is big and stressful. 4) Various symptoms related to digestive, respiratory, circulatory and reproductive system are represented by Sik-jeok. - Contemporarily women uterine or ovarian disease and back pain are mostly caused by Sik-jeok 5) Pediatric disease are mostly caused by Sik-jeok. 6) Treatment of Sik-jeok is light eating and if it is serious, you have to induce vomiting or diarrhea. Commonly used drugs are digestive medicine and invigorative medicine 7) To prevent Sik-jeok, you should forbid to eat until you are satisfied and wear warm clothes and continue to do spleen and genital do-in-beop.

• Journal of Astronomy and Space Sciences
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• v.20 no.4
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• pp.299-312
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• 2003

Earth to Mars ballistic mission opportunities from Naro Space Center are studied. Determining ballistic mission opportunities can be divided into two major parts, i.e. the launch window and the daily launch window determination. At the launch window determination parts, Porkchop diagrams of Earth launch C3 magnitude, total mission duration, declination of $V_{\infty}$ vector at the Earth launch, and declination & right ascension of $V_{\infty}$ vector at the Mars arrival are examined. The location of launch site and rotation effects of the Earth are considered during the daily launch window determination parts. Using Lambert method, various Porkchop diagrams of launching in 2027 are examined for example. The daily launch window of Naro Space Center at that year was checked to verify the launch possibility by comparing with the Kennedy Space Center.