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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Astronomy and Space Sciences
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Journal DOI :
The Korean Space Science Society
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Volume & Issues
Volume 25, Issue 4 - Dec 2008
Volume 25, Issue 3 - Sep 2008
Volume 25, Issue 2 - Jun 2008
Volume 25, Issue 1 - Mar 2008
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TITIUS-BODE'S Relation and 55 Cancri
Chang, Heon-Young ;
Journal of Astronomy and Space Sciences, volume 25, issue 3, 2008, Pages 239~244
DOI : 10.5140/JASS.2008.25.3.239
Two kinds of important issues on Titius-Bode's relation have been discussed up to now: one is if there is a simple mathematical relation between distances of natural bodies orbiting a central body, and the other is if there is any physical basis for such a relation. These may be tackled by answering a question whether Titius-Bode's relation is valid universally in exo-planetary systems. We have examined whether Titius Bode's relation is also applicable to exo-planetary systems by statistically studying the distribution of the ratio of rotational periods of two planets in an exo-planetary system, 55 Cnc, by comparing it with that derived from Titius-Bode's relation. We find that the distribution of the ratio of rotational periods of randomly chosen two planets in the 55 Cnc system is apparently inconsistent with that derived from Titius-Bode's relation. The probability that two data sets are drawn from the same distribution function is 50%. We also find that the Fourier power spectra show that the distribution of the semi-major axis of planets in the 55 Cnc system seems to be stretched. We conclude by pointing out that large numbers of planets should be examined to more convincingly explain the distribution of the distance of planetary formation regions.
The Near-IR TRGB Magnitude and Distance Modulus to NGC 185
Sohn, Y.J. ; Kang, A. ; Han, W. ; Park, J.H. ; Kim, H.I. ; Kim, J.W. ; Shin, I.G. ; Chun, S.H. ;
Journal of Astronomy and Space Sciences, volume 25, issue 3, 2008, Pages 245~248
DOI : 10.5140/JASS.2008.25.3.245
We determined values of distance modulus to nearby dwarf galaxy NGC 185 from the Tip of Red-Giant Branch (TRGB) method. Apparent magnitudes of the TRGB are estimated from the near-infrared JHK luminosity functions (LFs) of the resolved giant branch stars. Theoretical absolute magnitudes of the TRGB in near-infrared bands have been extracted from the Yonsei-Yale isochrones. The observed apparent and theoretical absolute magnitudes of the TRGB provide values of distance modulus to NGC 185 as (m - M) =
for J,H, and K bands, respectively. Distance modulus in bolometric magnitude is also derived as (m - M) =
Near-IR TRGB Distance to Nearby Dwarf Irregular Galaxy NGC 6822
Sohn, Y.J. ; Kang, A. ; Han, W. ; Park, J.H. ; Kim, H.I. ; Kim, J.W. ; Shin, I.G. ; Chun, S.H. ;
Journal of Astronomy and Space Sciences, volume 25, issue 3, 2008, Pages 249~254
DOI : 10.5140/JASS.2008.25.3.249
We report the distance modulus of nearby dwarf irregular galaxy NGC 6822 estimated from the so-called Tip of Red-giant Branch (TRGB) method. To detect the apparent magnitudes of the TRGB we use the color-magnitude diagrams (CMDs) and luminosity functions (LFs) in the near-infrared JHK bands. Foreground stars, main-sequence stars, and supergiant stars have been classified on the (g - K, g) plane and removed on the near-infrared CMDs, from which only RGB and AGB stars are remained on the CMDs and LFs. By applying the Savitzky-Golay filter to the obtained LFs and detecting the peak in the second derivative of the observed LFs, we determined the apparent magnitudes of the TRGB. Theoretical absolute magnitudes of the TRGB are estimated from Yonsei-Yale isochrones with the age of 12Gyr and the metallicity range of -2.0 <[Fe/H]< -0.5. The derived values of distance modulus to NGC 6822 are (m - M) =
for J, H, and K bands, respectively. Distance modulus in bolometric magnitude is also derived as (m - M) =
. We compare the derived values of the TRGB distance modulus to NGC 6822 in the near-infrared bands with the previous results in other bands.
Application of Analytic Solution in Relative Motion to Spacecraft Formation Flying in Elliptic Orbit
Cho, Han-Cheol ; Park, Sang-Young ; Choi, Kyu-Hong ;
Journal of Astronomy and Space Sciences, volume 25, issue 3, 2008, Pages 255~266
DOI : 10.5140/JASS.2008.25.3.255
The current paper presents application of a new analytic solution in general relative motion to spacecraft formation flying in an elliptic orbit. The calculus of variations is used to analytically find optimal trajectories and controls for the given problem. The inverse of the fundamental matrix associated with the dynamic equations is not required for the solution in the current study. It is verified that the optimal thrust vector is a function of the fundamental matrix of the given state equations. The cost function and the state vector during the reconfiguration can be analytically obtained as well. The results predict the form of optimal solutions in advance without having to solve the problem. Numerical simulation shows the brevity and the accuracy of the general analytic solutions developed in the current paper.
Generation of Meteorological Parameters for Tropospheric Delay on GNSS Signal
Jung, Sung-Wook ; Baek, Jeong-Ho ; Jo, Jung-Hyun ; Lee, Jae-Won ; Park, In-Kwan ; Cho, Sung-Ki ; Park, Jong-Uk ;
Journal of Astronomy and Space Sciences, volume 25, issue 3, 2008, Pages 267~282
DOI : 10.5140/JASS.2008.25.3.267
The GNSS (Global Navigation Satellite System) signal is delayed by the neutral atmosphere at the troposphere, so that the delay is one of major error sources for GNSS precise positioning. The tropospheric delay is an integrated refractive index along the path of GNSS signal. The refractive index is empirically related to standard meteorological variables, such as pressure, temperature and water vapor partial pressure, therefore the tropospheric delay could be calculated from them. In this paper, it is presented how to generate meteorological data where observation cannot be performed. KASI(Korea Astronomy & Space Science Institute) has operated 9 GPS (Global Positioning System) permanent stations equipped with co-located MET3A, which is a meteorological sensor. Meteorological data are generated from observations of MET3A by Ordinary Kriging. To compensate a blank of observation data, simple models which consider periodic characteristics for meteorological data, are employed.
Filtering Performance Analyizing for Relative Navigation Using Single Difference Carrier-Phase GPS
Park, In-Kwan ; Park, Sang-Young ; Choi, Kyu-Hong ; Choi, Sung-Ki ; Park, Jong-Uk ;
Journal of Astronomy and Space Sciences, volume 25, issue 3, 2008, Pages 283~290
DOI : 10.5140/JASS.2008.25.3.283
Satellite formation flying can provide the platform for interferometric observation to acquire the precise data and ensure the flexibility for space mission. This paper presents development and verification of an algorithm to estimate the baseline between formation flying satellites. To estimate a baseline(relative navigation) in real time, EKF(Extended Kalman Filter) and UKF(Unscented Kalman Filter) are used. Measurements for updating a state-vector in Kalman Filter are GPS single difference data. In results, The position errors in estimated baseline are converged to less than
in both EKF and UKF. And as using the two types of Kalman filter, it is clear that the unscented Kalman filter shows a relatively better performance than the extended Kalman filter by comparing an efficiency to the model which has a non-linearity.
Improvement of the Positioning Accuracy of a Single Frequency Receiver Using Observables of the Dual GPS Reference Stations
Choi, Byung-Kyu ; Park, Jong-Uk ; Lee, Sang-Jeong ;
Journal of Astronomy and Space Sciences, volume 25, issue 3, 2008, Pages 291~298
DOI : 10.5140/JASS.2008.25.3.291
With the growth of civil and commercial applications, the Global Navigation Satellite System(GNSS) that provides the positioning, navigation, and timing information affects to our life. In order to meet all the requirements of civilian user, new positioning technology with the accuracy of 10cm level has been applied and the positioning accuracy is getting improved. In this study, dual coverage(DAEJ, SUWN) GPS measurements were applied to improve the positioning accuracy for GPS L1 single frequency users. We processed some GPS data obtained from the distributed test sites in the wide area over Korea Peninsula. As a result, the combined solution output using dual coverage showed more improved positioning accuracy than that of single coverage.
Astronomical Calendar and Restoration Design of Clepsydra in the Silla era
Lee, Yong-Sam ; Jeong, Jang-Hae ; Kim, Sang-Hyuk ; Lee, Yong-Bok ;
Journal of Astronomy and Space Sciences, volume 25, issue 3, 2008, Pages 299~320
DOI : 10.5140/JASS.2008.25.3.299
We study on the astronomical calendars that was used in the Silla era. The calendars are deduced from the records in Samguksagi. They were influenced from calendaric system of Tang Dynasty, which are Lin duk calendar(麟德曆), Ta yen calendar(大衍曆) and Sun myung calendar(宣明曆). We analyse them in detail according to the time and duration of use. Water clock system of Unified Silla was used four water vessels for supplying water. We found the model from documents on ancient water clock that are appeared in the old Korean, Chinese and Japanese historical records. We have assumed the model of Unified Silla clepsydra is similar type with Chinese records during Tang dynasty and with Japanese reconstructed water clock in Temple Asoka. After fluid dynamic experiment, we decide the suitable diameter of supplying pipe and volume of the vessels used in the clepsydra. We introduce the experimental instruments and methods for accomplishing the clock. We designed and reconstructed the water clock of Unified Silla and float rods for measuring time, that is based on the Silla's calendaric system.
Conceptual Study of Simulated Software Test Bench Based On Processor Emulator for Integrated Performance Verification of Satellite On-board Software
Koo, Cheol-Hea ; Yang, Koon-Ho ; Choi, Seong-Bong ;
Journal of Astronomy and Space Sciences, volume 25, issue 3, 2008, Pages 321~328
DOI : 10.5140/JASS.2008.25.3.321
Software Test Bench should be simulated with maximum quality to real execution environment in order to verify the performance of software which is changed or newly developed. And especially faults detection and recovery are crucial function of the performance test environment. Simulated Software Test Bench based on processor emulator is attractive and can be available prior to hardware Software Test Bench if real time performance aspect is ignored. In this paper, the results of conceptual study for developing the simulated Software Test Bench are presented.