• Journal of Astronomy and Space Sciences
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• v.20 no.4
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• pp.319-326
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• 2003

The motion of each satellite in a tethered satellite system is non-Keplerian in the Earth's gravitational field. In this paper, the tether perturbation force is formulated and compared with the perturbation force due to the Earth's oblateness. Also, the center of mass motion of the tethered satellite system is analyzed. The tether perturbing force on the one of satellites in a tethered satellite system is much bigger than the Earth's oblateness perturbation. The two-body motion approximation of the center of mass is acceptable to describe the motion of the system, when the libration is small.

• Journal of Astronomy and Space Sciences
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• v.4 no.1
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• pp.47-54
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• 1987

Earth currents with 10~20 ${\mu}A$ flow due to a magnetic induction by large currents flowing through the ionosphere. In order to measure the behaviour of ionosphere indirectly, earth currents will be measured and the results will be reported.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.1
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• pp.54.1-54.1
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• 2014

Kyung Hee University has been developing a CubeSat for the space science mission called SIGMA (Scientific cubesat with Instrument for Global Magnetic field and rAdiation), which includes TEPC (Tissue Equivalent Proportional Counter) and a magnetometer. SIGMA has a 3-unit CubeSat, and the weight is about 3.2 kg. The main payload is TEPC which can measure the Linear Energy Transfer (LET) spectrum and calculate the equivalent dose for the complicated radiation field in the space. The magnetometer is a secondary payload using a miniaturized fluxgate magnetometer. We expect it to have a 1 nT resolution in the dynamic range of ${\pm}65535$ nT. An Attitude Control System (ACS) spins the SIGMA spacecraft 4 rpm with the spin axis perpendicular to the ecliptic plane. Full duplex communication is consists of VHF uplink and S-band and UHF downlink. In this paper, we introduce the system design and the scientific purpose of the SIGMA CubeSat mission.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.807-812
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• 2008

The various attempts is made to solve the energy and environment problems. In addition, people interested in their life quality want the more eco-friendly living space. So we suggested that the earth-sheltered house could be one of the eco-friendly and low energy consuming houses to meet the social interest. And we also made data for design of the earth-sheltered house to be applicable to climate of Korea. In this study, a simulation was performed to estimate a boundary temperature according to earth sheltering thickness at the earth-sheltered part(exterior wall) in the case of earth sheltering on the plane ground not using a sloped site. And we analyzed the reduction of a thermal load by using this boundary temperature. We also compared a case of earth sheltering at the vertical wall with a case of earth sheltering at the roof to know the thermal reduction effect of a case of earth sheltering at the vertical wall.

• Journal of The Korean Astronomical Society
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• v.56 no.1
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• pp.117-124
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• 2023

A Forbush decrease (FD) is a depression of cosmic ray (CR) intensity observed by ground-based neutron monitors (NMs). The CR intensity is thought to be modulated by the heliospheric magnetic structures including the interplanetary coronal mass ejection (ICME) surrounding the Earth. The different magnitude of the decreasing in intensity at each NM was explained only by the geomagnetic cutoff rigidity of the NM station. However, sometimes NMs of almost the same cutoff rigidity in northern and southern hemispheres observe the asymmetric intensity depression magnitudes of FD events. Thus, in this study we intend to see the effects on CR intensity modulation of FD event recorded at different NMs due to different ICME propagation directions as an additional parameter in the model explaining the CR modulation. Fortunately, since 2006 the coronagraphs of twin spacecraft of the STEREO mission allow us to infer the propagation direction of ICME associated with the FD event in 3-dimension with respect to the Earth. We suggest the hypothesis that the asymmetric CR modulations of FD events are determined by the propagation directions of the associated ICMEs.

• Journal of The Korean Astronomical Society
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• v.47 no.1
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• pp.41-41
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• 2014

The equivalent phase lag ${\varepsilon}_{lmpq}$ of Earth tide suggested by Lambeck have been found reasonable. Due to a mistake in his calculation, the author falsely claimed that those are too large. However, the main contents of the article are valid and not affected by this mistake.

• 한국지구물리탐사학회:학술대회논문집
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• 2011.10a
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• pp.97-98
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• 2011

• Journal of Positioning, Navigation, and Timing
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• v.12 no.4
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• pp.335-342
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• 2023

Lunar Navigation Satellite System refers to a constellation of satellite providing PNT services on the moon. LNSS consists of main satellite and navigation satellites. Navigation satellites orbiting around the moon and a main satellite moves the area between the moon and the L2 point. The navigation satellite performs the same role as the Earth's GNSS satellite, and the main satellite communicates with the Earth for time synchronization. Due to the effect of the non-uniform shape of the moon, it is necessary to focus on the influence of the lunar gravitational field when designing the orbit simulation for navigation satellite. Since the main satellite is farther away from the moon than the navigation satellite, both the earth's gravity and the moon's gravity must be considered simultaneously when designing the orbit simulation for main satellite. Therefore, the main satellite orbit simulation must be designed through the three-body problem between the Earth, the moon, and the main satellite. In this paper, the orbit simulation tool for main satellite and navigation satellite required for LNSS was designed. The orbit simulation considers the environment characteristics of the moon. As a result of comparing long-term data (180 days) with the commercial program GMAT, it was confirmed that there was an error of about 1 m.

• Journal of the Korean Society of Earth Science Education
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• v.5 no.3
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• pp.307-315
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• 2012

The purpose of this study was to examine the effects of small inquiry method on space perception ability and creative personality. Testees of this research are 36 elementary pre-service teachers taking an astronomical observation class. Doing inquiry activity after 36 elementary pre-service teachers are classified into 6 Jigsaw small inquiry. Learning activity was split into two groups, expert group and a population. To find out research outcome, pre-test was executed space perception ability test, creative personality test. Analysis of test result was accomplished with statistical package SPSS 18.0 paired t testing hypothesis. The results of this study are as follows. First, 'source of season change' class using Jigsaw small inquiry method has effect on space perception ability improvement. This was interpreted that space perception ability improvement was effective because characteristic of Jigsaw small inquiry is made up of lots of semin Second, 'source of season change' class using Jigsaw small inquiry method has no effect on creative personality. This was interpreted that experiment and discussion activity getting accomplished in a short time has no effect on qualitative characterizing Creative Personality improvement.

• Bulletin of the Korean Space Science Society
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• 2009.04a
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• pp.39.3-39.3
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• 2009