• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.11
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• pp.1021-1032
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• 2011

This paper presents the results of a parametric study for the design of optimal Earth-Moon transfer trajectory using mixed impulsive and continuous thrust. Various types of the optimal Earth-Moon transfer trajectories were designed by adjusting the relative weight between the impulsive and the continuous thrust, and flight time. Two very different transfer trajectories can be obtained by different combination of design parameters. Furthermore, it was found that all thus designed trajectories permit the ballistic capture by the Moon gravity. Finally, the required thrust profiles are presented and analyzed in detail.

• ETRI Journal
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• v.14 no.1
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• pp.1-14
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• 1992

정지궤도에 위치한 위성에 있어서 지구에 의한 식은 일년에 두 기간에 걸쳐서 정기적으로 발생한다. 반면에 달에 의한 식은 궤도의 위치에 따라 불규칙적으로 발생하다. 식이 일어날 때 위성은 태양을 이용한 전력생산을 할 수 없게 되기 때문에 식시간에 대한 예측은 정지궤도상의 통신위성 또는 방송위성을 운용하는데 있어서 매우 중요하다. 본 연구에서는 정지위성을 공칭위치에 고정시켜 놓고, 적도 좌표계에서 태양과 달의 시간에 따른 위치를 계산함으로써 지구와 달에 의한 식을 예측하였다. 또한 정지위성의 위치유지 각 한계점에서의 식을 예측해서 궤도위치에 따른 식시간과 식깊이를 비교해 보았다. 정지궤도상의 위성은 1995년에 발사될 동경 $116^{\circ}$의 무궁화 위성으로 하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.843-854
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• 2009

For preparing Korean lunar missions, optimal Earth-Moon transfer trajectory is designed using continuous low thrust. Using both constant and variable low thrusting method, "End-to-End" mission analysis is made from beginning of the Earth departure to the final lunar arrival. Spacecraft's equations of motion is expressed using N-body dynamics including the gravitational effects due to the Earth, Moon, Sun and also with Earth's $J_2$ effects. Planets' exact locations are computed accurately with JPL's DE405 ephemeris. As a results, optimal thrust steering angle's characteristics are discovered which showed almost tangential direction burns at the near of central planets. Also, it is confirmed that variable low thrusting method is more efficient than constant thrusting method, and can save about 5% of fuel consumption. Presented algorithm and various results will give numerous insights into the future Korea's Lunar missions using low thrust engines. Also, it is expected to be used as a basis of more detailed mission analyzing tool.

• Journal of the Korean earth science society
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• v.27 no.4
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• pp.353-363
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• 2006

This study investigates how the lunar phases drawing module-applied instruction affects high school students' conceptual changes of the lunar phases. 46 juniors in a high school were given the module instruction on drawing the lunar phases, and then interviews were conducted to verify conceptual changes in subjects' recognition structures. The types of students' misconceptions of the lunar phases change before the instruction were as follows. Type S is that the Earth's shadow covers the moon. Type SR is that one has both misconception of Type S and a scientific concept at the same time according to the positional relationships. The scientific concept means that an observer sees a moon's part which reflects sunlight. Type SB is that the Earth's shadow covers the moon or the moon can be seen or not by the background's brightness according to the positional relationships. The last Type SRB includes all three above-mentioned types, and it explains the lunar phases at each position. As a result of the module-based instruction, 26 out of 36 subjects built up the scientific concept and 10 students did not. 7 out of the 11 Type S and 3 out of the 17 Type SR students did not, either. Especially, type S students did not change their preconception that the phases of moon change were done by the earth's shadow. Here, their preconception is too much strong; as they solve problems, their preconception is more beneficial, comparing to the method which it is presented from the module. This fact supports that it is difficult for students to discard preconception.

• Journal of the Korean earth science society
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• v.27 no.6
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• pp.591-605
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• 2006

The purpose of this study is to investigate the relationship between lunar and earth rotation, by quantitatively describing the rotation of lunar configuration which is observed during the lunar diurnal motion. Our research suggests that observation of the lunar diurnal motion could be used as a study topic in the earth science courses. The rotation of the lunar configuration is an apparent phenomenon that can be seen when an observer. standing on the ground. looks at the moon as if the lunar dark configuration rotates on the basis of horizontal line. In spite its competence as a study topic because it is observable by naked eyes, there are only few major textbooks that introduce this phenomenon with regard to the earth rotation. Therefore, this study induced the mathematical principle of the lunar rotation in detail and proposed that this could be developed as a scientific inquiry through practical observation. In addition, an analytical proof and qualitative method of explanation of the lunar reverse rotation were also presented.

• Journal of the Korean earth science society
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• v.25 no.7
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• pp.519-531
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• 2004

The purpose of this study was to ascertain high school student ideas on the motion of the Earth and moon by cognitive level. For this study, five students determined to be of high, middle and low cognitive level selected from 73 10th-grade students at a high school located in Suwon, Gyeonggido. The results of this study were as follows: first, students at the high cognitive level had comparatively more logical and scientific conception on the revolution and rotation of the Earth and moon. second, students at the middle cognitive level, generally had a passive learning attitude to unconditionally memorize learned contents, so they were apt to forget learned contents, also their recognized conception was not enlarged. In addition, they had native theories, intuitive ideas and misconceptions as well as made logical errors in the course of explanation for the motion of the Earth and moon. In the course of explanation for the phases of the moon and the cause of change of season, because of their scientific conception, the students made more and more errors in conception. finally students at the low cognitive level were not willing to think logically and positively and were very passive in the attitude to recognize conception. In addition, they have learned helplessness on the grounds that they have low scholastic achievement specially in science.

• Bulletin of the Korean Space Science Society
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• 2010.04a
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• pp.26.2-26.2
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• 2010

이 연구는 Ashen light 측정을 통해 전 지구 반사율을 구하는 통합적 광선 추적 모델을 구성하고 그 수치모사 성능을 검증하는데 목적을 두고 있다. 통합적 광선 추적 모델은 태양-지구-달 시스템에 대하여 태양 복사에너지의 광경로를 추적함으로써 최종적으로 저궤도 상에 존재하는 광학계에 도달하는 Ashen light과 moonshine의 조도를 수치 모사하는 기법이다. Ashen light은 구형의 태양에서 출발한 $1.626\times10^{26}W$의 에너지를 가지는 400nm에서 700nm 파장대역의 빛이 램버시안 특성을 지니는 구형의 지구에서 반사된 후 램버시안 특성을 가지는 구형의 달에서 재 반사되어 저궤도상의 광학계로 입사하는 빛이고, moonshine은 달에서 직접 반사되어 저궤도상의 광학계로 입사하는 빛이다. 통합적 광선 추적 수치 모사를 이용하여 구한 Ashen light과 moonshine의 조도는 1차 근사 해석적 방법을 이용한 계산 결과와 측정 오차 범위 이내의 오차를 보였다. 최종 연구 결과 Ashen light과 moonshine의 조도를 이용하여 구한 지구 반사율과 1차 근사 해석적 방법을 이용한 지구 반사율 계산의 결과가 유사함을 증명하였다.

• 대한지구과학교육학회:학술대회논문집
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• 2011.01a
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• pp.31-32
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• 2011

• Journal of the Korean Society of Earth Science Education
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• v.11 no.3
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• pp.237-243
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• 2018

The purpose of this study is to analyze the contents related to a subject 'Earth and Mooon' from elementary science textbooks of the 2009 revised curriculum and elementary science textbooks of the 2015 revised curriculum. For the research, the team selected and analyzed the contents of the 'Earth and Moon' unit in the elementary science textbooks of the 2009 revised curriculum and 2015 revised curriculum. As a result of the research, first, there has been no significant change in achievement standards of the curriculum as the science textbook revised from 2009 curriculum to 2015 curriculum. Second, the two curriculum did not differ much in specific textbook contents statement or development, but they showed much change in presentation of exploration activities in curriculum as well as the specific exploration activities presented in the textbooks. Third, compared to science textbooks of the 2009 revision the 2015 revision used more pictures and illustrations. Forth, there have been few changes related to experimental observation, but the activities to organize the unit in 2015 revision have been strengthened compared to the 2009 revision.

• Journal of Korean Elementary Science Education
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• v.27 no.4
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• pp.385-398
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• 2008

The purpose of this study is to understand the effect of The Model of Phases of the Moon on conception changes for preservice teachers. The researcher interviewed two preservice teachers under the agreement with them on their participation in the research just before he performed a class using The New Model of Phases of the Moon. The post-interview with the same content as the pre-interview was preformed one month later. The main content of the interview is as follows; 'Explain the shape of the Moon by drawing it.', 'Explain the relative different position among the Sun, Earth, and Moon depending on phases of the Moon by drawing them.', 'What do you think of the cause of phases of the Moon?', 'Draw a picture to explain why we always see only one side of the moon.' The results of the research are as follows. First, the class with New Model of Phases of the Moon was able to perceive the relationship of Sun, Earth, and Moon in three-dimensions rather than in two-dimensions and it helped to change their misconception that the Moon's shadow causes the Moon's shape. Secondly, the class with New Model of Phases of the Moon helped preservice teachers understand better the different positional relationships among the Sun, Earth, and Moon depending on the Moon shapes. Third, the class adopting the New Model of Phases of the Moon help preservice teachers form scientific conceptions on the causes of phase change of the Moon. Fourth, the class with the New Model of Phases of the Moon is not appropriate for explaining the reason why only one face of the Moon is seen. Based upon the results above, the researcher realized the limitation of this model and suggested that this model would help learners understand phase change of the Moon and increase space perception ability.