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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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The Korean Space Science Society
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Volume 17, Issue 2 - Dec 2000
Volume 17, Issue 1 - Jun 2000
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ABSORPTION LINE GRADIENTS IN THE BULGE OF Sa TYPE GALAXY M104
Sohn, Young-Jong ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 125~132
Long-slit spectra, covering the wavelength range 4050~5150
, have been used to investigate the radial behavior of absorption line features (G4300, Fe4383, Ca4455, Fe4531, Fe4668, and H
) along the major and minor axes of the bulge of M104. The heliocentric recession velocity of M104 has been derived as 1260
. The strength of a number of metal absorption lines is decreasing with increasing radius, and the minor axis shows much steeper radial line gradients than the major axis. Line index of H
has an opposite trend to other metal lines, i.e., increasing outward. The results in this paper imply that the properties of absorption line index distribution in M104 bulge have in many aspects similar trends to those of elliptical galaxies.
METALLICITY OF GLOBULAR CLUSTER M13 FROM VI CCD PHOTOMETRY
Sohn, Young-Jong ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 133~140
From the VI images of M13, obtained by using 2K CCD camera and the BOAO 1.8m telescope, we derive the(V - I) - V CMD of M13. From the shapes of red giant branch, the magnitude of horizontal branch, and the giant branch bump on the constructed CMD, we determined the metallicity of the globular cluster to be 1.74
-1.41. The good agreement between our determination of [Fe/H] and those determined by using other methods implies that the morphology of red giant and horizontal branches on (V - I) - V CMD's can be good indirect metallicity indicators of Galactic globular clusters.
GEOTAIL SPACECRAFT OBSERVATIONS OF NEAR-TAIL DIPOLARIZATION AND PLASMA FLOW DURING THE SUBSTORM EXPANSION
Lee, D.Y. ; Min, K.W. ; Lee, E.S. ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 141~146
Some observational features on the July 5, 1995 substorm event are presented using the data from the Geotail satellite which was located at near-Earth plasma sheet,
, and quite close to the onset sector. Near-tail magnetic field reveals the typical dipolarizations starting ar ∼ 11-4 UT until ∼ 1113 UT. During the interval, two dipolarizations occur: First dipolarization is not strong and accompanies only weak(<150km/s) earthward/dawnward plasma flows, and in the second dipolarization that follows shortly, rather large amplitude magnetic fluctuations are seen, but it initiates with no significant earthward flow. The earthward bursty flow with a maximum speed of > 450km/s was observed, but delayed by ∼ 1 min with respect to the second dipolarization initiation. These features are in conflict with the flow-braking scenario for the substorm. Rather they fit better in the near-tail current disruption scenario.
ABUNDANCES IN COMETS USING THE ULTRAVIOLET BANDS OF
Kim, Sang-Joon ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 147~150
A fluorescent equilibrium model for the 1-0 band of the A-X system of
has been constructed. Line positions and intensities have been calculated for possible future spectroscopic observations of these bands from space in order to derive
ratios in comets. It is demonstrated that the strong lines of the 1-0 band can be observable for a moderately bright comet using a high resolution spectrometer with a reasonable exposure time.
GENERAL PROPERTIES OF NEAR-CONTACT BINARIES
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 151~162
The general properties of the NCBs, divided into A and F types according to their spectral types, have been presented. The evolutionary status of the F type near-contact binaries are closer to that of the contact systems, i.e., W UMa type binaries, if it is assumed that the evolution of the NCBs is governed by the thermal relaxation oscillation theory. The mass-radius relation, mass-luminosity relation and H-R diagram of the NCBs provide that the A type NCBs suffer from more active mass transfer than F types. The components of the NCBs ar still in main-sequence like W UMa type stars and their two components lines parallel to the ZAMS.
AN APPLICATION OF WD MODEL TO EB TYPE CONTACT BINARY SYSTEM
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 163~172
The EB type contact binaries show large temperature difference
between two components. Thus we have modified the mode 3 of the WD program to adjust albedos, limb darkening coefficients and gravity darkening exponents for both components of such binaries, while the values for those parameters should be same for both components in the original WD program. Both of the modified and the original versions have been applied to the EB type contact binaries such as DO Cas, GO Cyg, and FS Lup. The computed light curves with modified version fit better to the observations.
A PERIOD STUDY OF THE CLOSE BINARY V651 CASSIOPEIAE
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 173~180
All times of minimum light of V651 Cas, which is still less studied so far, were analyzed. From our analysis, it was found that the orbital period of the system may have varied in a periodic manner. After assuming that the period change is produced by the light-time effect due to a third body in the system, attempts to derive the orbital elements of the light-time orbit were made. The resultant values for the period, semi-amplitude, and eccentricity of the light-time orbit were 6.
, and 0.77, respectively. The future observations of times of minimum light of V651 Cas are needed to confirm the existence of the third body we suggested in this paper.
AN ANALYSIS OF THE LIGHT AND RADIAL VELOCITY CURVES OF DO CAS
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 181~188
DO Cas is a short period (P=0.68day) eclipsing binary star and is classified as a near-contact binary by Shaw(1990). There is no published radial velocity curve for this short period binary after Mannino(1958). Hill(1991) suspected that Mannino's radial velocity curve had some serious mistake. So, we scanned the original plates used by Mannino with PDS and the spectra were employed to IRAF packages to estimate the radial velocities. The radial velocity curve and the BVR light curves made by us in 1998 were analyzed simultaneously with Wilson-Devinney code. We found that DO Cas is a contact or near-contact binary which the primary component fills its Roche lobe and we also estimated the absolute dimensions of each components of this system.
STARSPOT MODEL OF RS CVn TYPE BINARY SZ PSC
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 189~198
The emission lines of the ultraviolet region and the light curves of the optical region have been analyzed to investigate the distorted light curves of SZ Psc. The Mg II emission lines of the IUE spectra confirmed that the chromospheric activity of SZ Psc occurs on the K1 IV star. The distorted light curves in the optical region have been analyzed by the spot model where the spots are on the K1 IV star as the result of the chromospheric activity. The complete photometric solution could be deduced for SZ Psc by the good fitness with the spot model.
NARROW-BAND SPECTROPHOTOMETRY OF COMET HALE-BOPP (C/1995 O1) NEAR PERIHELION I : PHOTOMETRIC BEHAVIOR OF
, CN MOLECULAR BANDS
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 199~210
We present the results from narrow-band spectrophotometry of Comet Hale-Bopp (C/1995 O1) near perihelion obtained at Sobaeksan Optical Astronomy Observatory 61cm telescope equipped with PM 512 CCD camera(512
512, 0.5"/pixel) and narrow-band filter set for the comet on 19 nights from February 21 to May 1, 1997. We discuss molecular emission band morphology and photometric behavior of Comet Hale-Bopp. The morphology of CN band shows more symmetric light distributions than
bands. On other hand,
band have more compact light distributions than CN band. Similar to wide-band image, molecular band morphology shows spiral structures at the core of the comet. The CN surface brightness variation with changing heliocentric distance shows difference from those of
. The brightness, however, of these molecular bands near perihelion shows previously known 7day period light variations.
DESIGN CONCEPT FOR THE RETROFIT KAO 1M ROBOTIC TELESCOPE
Han, Won-Yong ; Mack, Peter ; Park, Jang-Hyun ; Jin, Ho ; Lee, Woo-Baik ; Lee, Chung-Uk ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 211~220
Korea Astronomy Observatory(KAO) is working to retrofit its 1m robotic telescope in collaboration with a company (ACE, Astronomical Consultants & Equipment). The telescope system is being totally refurbished to make a fully automatic telescope which can operate in both interactive and fully autonomous robotic modes. Progress has been made in design and manufacturing of the telescope mount, mechanics, and optical performance system tests are being made for re-configured primary and secondary mirrors. The optical system is designed to collect 80% incident light within 0.5 arcsec with f/7.5 Ritchey-Chretien design. The telescope mount is an equatorial fork with a friction drive system. The design allows fully programmable tracking speeds with typical range of 15 arcsec/sec with accuracy of
arcsec/hour. The mount system has integral pointing model software to correct for refraction, and all mechanical errors and misalignments. The pointing model will permit positioning to better than 30 arcsec RMS within
from zenith and 45 arcsec RMS elsewhere on the sky. The software is designed for interactive, remote and robotic modes of operation. In interactive and remote mode the user can manually enter coordinates or retrieve them from a computer file. In robotic mode the telescope controller downloads the coordinates in the order determined by the scheduler. The telescope will be equipped with a CCD camera and will be accessible via the internet.
DEVELOPMENT OF WIDEBAND TUNABLE E-BAND(60-70 GHz) GUNN OSCILLATOR
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 221~232
A Gunn waveguide-oscillator, mechanically tunable from 60 to 70 GHz, has been developed for use as a local oscillator(LO) is millimeter radio telescope. Disc size, post size and characteristics of Gunn diode have an effect on the frequency tuning characteristics of Gunn oscillator. In this paper we report experimental results and design criteria for a wideband tunable Gunn oscillator. The developed Gunn oscillator has been used in the 100/150 GHz band dual channel receiver for the Taeduk Radio Astronomy Observatory.
BRIEF REPORTS ON KAISTSAT-4 MISSION ANALYSIS
Seon, J. ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 233~240
Five scientific instruments are planned on KAISTSAT-4 that is scheduled to be launched in 2002. A far ultra-violet imaging spectrograph and a set of space plasma instruments are currently being designed. The imaging spectrograph will make observations of astronomical objects and Earth's upper atmosphere. The plasma instrumentation is capable of fast measuring the thermal magnetosphere plasmas, cold ionospheric plasmas and the Earth's magnetic fields. Major system drivers and constraints on the payloads as well as the spacecraft are identified. A preliminary analysis of the K-4 mission has been undertaken with the system requirements that are derived from the system drivers. Detailed investigation shows that Sun-synchronous orbits with approximate altitudes of 800km are optimal to satisfy the identified requirements. Comparisons with other orbits of different inclinations are also shown. Four operation modes and a daily schedule of spacecraft maneuver are found from the Sun-synchronous orbital model. It is shown that the scientific objectives of K-4 can be achieved with moderate levels of design and operation risks.
SOLAR CYCLE VARIATION OF UPPER THERMOSPHERIC TEMPERATURE OVER KING SEJONG STATION, ANTARCTICA
Chung, Jong-Kyun ; Won, Young-In ; Kim, Yong-Ha ; Lee, Bang-Yong ; Kim, Jhoon ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 241~248
A groung Fabry-Perot interferometer has been used to measure atomic oxygen nightglow (OI 630.0nm) from the thermosphere (about 250km) at King Sejong station (KSS, geographic:
E), Antarctica. While numerous studies of the thermosphere have been performed on high latitude using ground-based Fabry-Perot interferometers, the thermospheric measurements in the Southern Hemisphere are relatively new and sparse. Therefore, the nightglow measurements at KSS play an important role in extending the thermospheric studies to the Southern Hemisphere. In this study, we investigated the effects of the geomagnetic and solar activities on the thermospheric neutral temperatures that have been observed at KSS in 1989 and 1997. The measured average temperatures are 1400K in 1989 and 800K in 1997, reflecting the influence of the solar activity. The measurements were compared with empirical models, MSIS-86 and semi-empirical model, VSH.
A STUDY ON FUEL ESTIMATION ALGORITHMS FOR A GEOSTATIONARY COMMUNICATION & BROADCASTING SATELLITE
Eun, Jeong-Won ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 249~256
It has been developed to calculate fuel budget for a geostationary communication and broadcasting satellite. It is quite essential that the pre-launch fuel budget estimation must account for the deterministic transfer and drift orbit maneuver requirements. After on-station, the calculation of satellite lifetime should be based on the estimation of remaining fuel and assessment of actual performance. These estimations step from the proper algorithms to produce the prediction of satellite lifetime. This paper concentrates on the fuel estimation method that was studied for calculation of the propellant budget by using the given algorithms. Applications of this method are discussed for a communication and broadcasting satellite.
A SYSTEM DESIGN AND ANALYSIS FOR SATELLITE COMMUNICATION LINK
Chung, Tae-Jin ; Eun, Jong-Won ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 257~266
A satellite RF communication link is analyzed based on a simple fundamental equations by systematic approach in this paper. The number of variables related to a design and analysis of satellite RF link is often a dozen or more, thus it is a tedious and time-consuming task. With the given input data, the important parameters are calculated step by step and three communication characteristics such as communication channel capacity, carrier-to-noise ratio(CNR) at the satellite and ground station are analyzed. It gives very useful information to the system engineers for designing and analyzing the overall satellite communication system in the conceptual design phase.
DEVELOPMENT OF PYRAMIDAL TYPE 2-AXES ANALOG SUN SENSOR
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 267~276
PSS(Pyramidal type 2-axes Analog Sun Sensor) which will be used for KAISTSAT-4 is designed to be small, light, low in power consumptions, and adequate for small satellite attitude sensor. The PSS for the KAISTSAT-4 consists of the pyramidal structure, solar cells and amplifier. The pyramidal structure is suitable for the 2-axes sensing, Solar cells are made up of a rectangular shape of crystal silicon. The PSS measures the angle of incident light and initial satellite attitude measurement, and provides an alarm for the sunlight-sensitive payloads. This paper explains the PSS structure and the characteristic test result about the PSS with
in FOV, less than
DEVELOPMENT OF OZONE DETECTOR FOR KSR-III AND PRELIMINARY TEST RESULTS
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 277~284
KARI(Korea Aerospace Research Institute) has measured the ozone density profiles over the Korean Peninsular since the launch of the Korean Sounding Rocket-I (KSR-I) in 1993. The purpose of ozone measurements is to obtain the stratospheric and mesospheric vertical ozone density profiles over the Korean Peninsular with solar UV radiometers. With the visible channel of the radiometer, the attitude variation of the rocket was corrected and compensated. Developed system is based on ozone detector designs onboard the KSR-I and KSR-II. We discuss the development of ozone detector which will be onboard the KSR-III and its circuit and vibration test results for EM model.
POST LAUNCH MISSION ANALYSIS FOR THE KOMPSAT-1
Lee, Byoung-Sun ; Lee, Jeong-Sook ; Kim, Jong-Ah ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 285~294
The post-launch mission analysis of the KOMPSAT-1 spacecraft was carried out. The injection accuracy of the Taurus launch vehicle was analyzed by comparison of the target and the realized orbit parameters. The tracking station contact analysis was also performed based on the state vectors applied at the day of launch. The offset angles between the predicted orbit and realized orbit were calculated for various tracking stations. The injection orbit parameters of the KOMPSAT-1 were analyzed for the possible options in Launch and Early Orbit Phase(LEOP) operations. Variations of the Local Time of Ascending Node(LTAN) were also obtained.
RADIOMETRIC CALIBRATION OF OSMI IMAGERY USING SOLAR CALIBRATION
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 295~308
OSMI(Ocean Scanning Multi-Spectral Imager) raw image data(Level 0) were acquired and radiometrically corrected. We have applied two methods, using solar & dark calibration data from OSMI sensor and comparing with the SeaWiFS data, to the radiometric correction of OSMI raw image data. First, we could get the values of the gain and the offset for each pixel and each band from comparing the solar & dark calibration data with the solar input radiance values, calculated from the transmittance, BRDF (Bidirectional Reflectance Distribution Function) and the solar incidence angle(
) of OSMI sensor. Applying this calibration data to OSMI raw image data, we got the two odd results, the lower value of the radiometric corrected image data than the expected value, and the Venetian Blind Effect in the radiometric corrected image data. Second, we could get the reasonable results from comparing OSMI raw image data with the SeaWiFS data, and get a new problem of OSMI sensor.
SUN INCIDENCE ANGLE ANALYSIS OF KOMPSTAT-2 PAYLOAD DURING NORMAL MISSION OPERATIONS
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 309~316
KOMPSAT-2 will carry MSC(Multi-Spectral Camera) which provides 1m resolution panchromatic and 4m resolution multi-spectral images at the altitude of 685km sun-synchronous mission orbit. The mission operation of KOMSPAT-2 is to provide the earth observation using MSC with nadir pointing. KOMPSAT-2 will also have the capability of roll/pitch tilt maneuver using reaction wheel of satellite as required. In order to protect MSC from thermal distortion as well as direct sunlight, MSC shall be operated within the constraint of sun incidence angle. It is expected that the sunlight will not violate the constraint of sun incidence angle for normal mission operations without roll/pitch maneuver. However, during roll/pitch tilt operations, optical module of MSC may be damaged by the sunlight. This study analyzed sun incidence angle of payload using KOMPSAT-2 AOCS (Attitude and Orbit Control Subsystem) Design and Performance Analysis Soft ware for KOMPSAT-2 normal mission operations.
PRELIMINARY REPORT: DESIGN AND TEST RESULTS OF KSR-3 ROCKET MAGNETOMETERS
Kim, Hyo-Min ; Jang, Min-Hwan ; Lee, Dong-Hun ; Ji, Jong-Hyun ; Kim, Sun-Mi ; Son, De-Rac ; Hwang, Seung-Hyun ;
Journal of Astronomy and Space Sciences, volume 17, issue 2, 2000, Pages 317~328
The solar wind contributes to the formation of unique space environment called the Earth's magnetosphere by various interactions with the Earth's magnetic field. Thus the solar-terrestrial environment affects the Earth's magnetic field, which can be observed with an instrument for the magnetic field measurement, the magnetometer usually mounted on the rocket and the satellite and based on the ground observatory. The magnetometer is a useful instrument for the spacecraft attitude control as well as the Earth's magnetic field measurements for the spacecraft purpose. In this paper, we present the preliminary design and test results of the two onboard magnetometers of KARI's (Korea Aerospace Research Institute) sounding rocket, KSR-3, which will be launched four times during the period of 2001-02. The KSR-3 magnetometers consist of the fluxgate magnetometer, MAG/AIM (Attitude Information Magnetometer) for acquiring the rocket flight attitude information, and of the search-coil magnetometer, MAG/SIM (Scientific Investigation Magnetometer) for the observation of the Earth's magnetic field fluctuations. With the MAG/AIM, the 3-axis attitude information can be acquired by the comparison of the resulting dc magnetic vector field with the IGRF (International Geomagnetic Reference Field). The Earth's magnetic field fluctuations ranging from 10 to 1,000 Hz can also be observed with the MAG/SIM measurement.