• 천문학회보
• /
• 제11권
• /
• pp.5.3-6
• /
• 1986

• 천문학회보
• /
• 제34권1호
• /
• pp.193-193
• /
• 2009

• Journal of Positioning, Navigation, and Timing
• /
• 제9권1호
• /
• pp.1-6
• /
• 2020

The Chinese BeiDou Satellite Navigation System consists of three kinds of constellations: the geostationary Earth orbit (GEO), the inclined geosynchronous satellite orbit (IGSO), and the medium Earth orbit (MEO). The BeiDou has expanded its service coverage from regional to global. Recently, the BeiDou has been widely used in ionospheric total electron content (TEC) research. In this study, we analyzed the BeiDou signals for ionospheric TEC monitoring over Jeju Island in South Korea. The BeiDou GEO TEC showed a clear pattern of diurnal variations. In addition, we compared the TEC values from the BeiDou GEO, the BeiDou IGSO, GPS, and International GNSS Service (IGS) Global Ionosphere Maps (GIM). There was a difference of about 5 TEC units between the BeiDou GEO and the IGS GIM. This may be due to the altitude difference between the different navigation satellites.

• 천문학회보
• /
• 제38권1호
• /
• pp.77.2-77.2
• /
• 2013

xIn the present work, we explored the effect of the radiation on the effective impact parameter for capture in a fully general relativistic manner. To summarize our results, evidently due to the radiation drag (the Poynting-Robertson effect), critical impact parameter of point particle gets larger by the factor of two, thus, the effective cross section of the luminous relativistic star becomes 4 times larger than that of the star without radiation emission. In addition, the finite size effect of the star adds up to this growth of the effective cross section.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 1996년도 한국우주과학회보 제5권2호
• /
• pp.19-19
• /
• 1996

No Abstract, See Full Text

• Journal of Astronomy and Space Sciences
• /
• 제35권4호
• /
• pp.279-286
• /
• 2018

Radar sensors are used for space situational awareness (SSA) to determine collision risk and detect re-entry of space objects. The capability of SSA radar system includes radar sensitivity such as the detectable radar cross-section as a function of range and tracking capability to indicate tracking time and measurement errors. The time duration of the target staying in a range cell is short; therefore, the signal-to-noise ratio cannot be improved through the pulse integration method used in pulse-Doppler signal processing. In this study, a method of improving the signal-to-noise ratio during range migration is presented. The improved detection performance from signal processing gains realized in this study can be used as a basis for comprehensively designing an SSA radar system.

• 대한지구과학교육학회지
• /
• 제6권3호
• /
• pp.252-260
• /
• 2013

The purpose of this study is find out the correlation of level of knowledge of pre-service elementary teacher with space perception ability on 'Earth and Space' of elementary science. During the second semester of 2013, for 15 weeks, the classes were conducted for 3 hours per week and we find out knowledge Understanding degree and select terms offered by 5th grade science courses 'The solar system and the stars', 'Earth and Moon', 'change of seasons' section and measured space perception ability degree of pre-service elementary school teacher with a questionnaire. We analyzed the correlation of understanding level of knowledge in the field of astronomy of pre-service elementary school teacher with space perception ability. The results of the study are presented as follows. First, pre-service elementary school teacher showed a low level of knowledge understanding as it goes the upper grades about upper concept in 'The solar system and the stars', 'Earth and Moon', 'change of seasons' section' of astronomy area of elementary science 'Earth and space sector'. The pre-service elementary school teachers needs to acquire knowledge of astronomy area in elementary school curriculum. Second, pre-service elementary school teacher showed that there are differences individually in 'finding solid body' of sub-element of space perception ability. This shows that 'finding solid body' factor is associated with space perception ability. Third, in the section of 'The earth and the Universe' for elementary education, 'Reflection' and 'Finding solid body' which are low-level components of space perception ability were verified that have a corelationship with general grades in the astronomy conception test.

• 천문학회보
• /
• 제28권1호
• /
• pp.37-37
• /
• 2003

• Journal of Astronomy and Space Sciences
• /
• 제36권4호
• /
• pp.235-248
• /
• 2019

This paper suggests a relative orbit control strategy for the CubeSat Astronomy by NASA and Yonsei using Virtual Telescope Alignment eXperiment (CANYVAL-X) mission whose main goal is to demonstrate an essential technique, which is an arrangement among two satellites and a specific celestial object, referred to as inertial alignment, for a next-generation virtual space telescope. The inertial alignment system is a relative orbit control system and has requirements for the relative state. Through the proposed orbit control strategy, consisting of separation, proximity keeping, and reconfiguration, the requirements will be satisfied. The separation direction of the two CubeSats with respect to the orbital plane is decided to provide advantageous initial condition to the orbit controller. Proximity keeping is accomplished by differential atmospheric drag control (DADC), which generates acceleration by changing the spacecraft's effective cross section via attitude control rather than consuming propellant. Reconfiguration is performed to meet the requirements after proximity keeping. Numerical simulations show that the requirements can be satisfied by the relative orbit control strategy. Furthermore, through numerical simulations, it is demonstrated that the inertial alignment can be achieved. A beacon signal had been received for several months after the launch; however, we have lost the signal at present.

• Journal of Astronomy and Space Sciences
• /
• 제10권1호
• /
• pp.1-16
• /
• 1993

Three typer of spin-axis attitude determination program for the geosynchronous transfer orbit spacecraft are developed. Deterministic closed-from algorithm, batch least-square algorithm and stabilized Kalman filter algorithm are used for implemetation of three programs. EUROSTAR bus model from British Aerospace is used for attitude sensor modelling. Attitude determinations using three programs are performed for the simulated sensor data according to INMARSAT 2-F1 prelaunch mission analysis.