간행물
Journal of Astronomy and Space Sciences KCI 등재 SCOPUS
- 발행기관 한국우주과학회
- 자료유형 학술지
- 간기 계간
- ISSN 2093-5587 (Print)2093-1409 (Online)
- 수록기간 1984 ~ 2022
- 주제분류 자연과학 > 천문학 자연과학 분류의 다른 간행물
- 십진분류KDC 443DDC 520
권호리스트/논문검색
제29권 1호 (2012년 3월) 13건
1.
2012.03
서비스 종료(열람 제한)
In this study, global positioning system (GPS)-derived precipitable water vapor (PWV) and microwave radiometer(MWR)-measured integrated water vapor (IWV) were compared and their characteristics were analyzed. Comparingthose two quantities for two years from August 2009, we found that GPS PWV estimates were larger than MWR IWV. Theaverage differenceover the entire test period was 1.1 mm and the standard deviation was 1.2 mm. When the discrepanciesbetween GPS PWV and MWR IWV were analyzed depending on season, the average difference was 0.7 mm and 1.9mm in the winter and summer months, respectively. Thus, the average difference was about 2.5 times larger in summerthan that in winter. However, MWR IWV measurements in the winter months were over-estimated than those in the summermonths as the water vapor content got larger. The results of the diurnal analysis showed that MWR IWV was underestimatedin the daytime, showing a difference of 0.8 mm. In the early morning hours, MWR IWV has a tendency to beover-estimated, with a difference of 1.3 mm with respect to GPS PWV.
2.
2012.03
서비스 종료(열람 제한)
In this paper, the authors introduced a new approach to find the optimal collision avoidance maneuver considering multi threatening objects within short period, while satisfying constraints on the fuel limit and the acceptable collision probability. A preliminary effort in applying a genetic algorithm (GA) to those kinds of problems has also been demon\-strated through a simulation study with a simple case problem and various fitness functions. And then, GA is applied to the complex case problem including multi-threatening objects. Two distinct collision avoidance maneuvers are dealt with: the first is in-track direction of collision avoidance maneuver. The second considers radial, in-track, cross-track direction maneuver. The results show that the first case violates the collision probability threshold, while the second case does not violate the threshold with satisfaction of all conditions. Various factors for analyzing and planning the optimal collision avoidance maneuver are also presented.
3.
2012.03
서비스 종료(열람 제한)
Yoo, Jae-Gun, Jin, Ho, Seon, Jong-Ho, Jeong, Yun-Hwang, Glaser, David, Lee, Dong-Hun, Lin, Robert P.
Thermal analysis and control design are prerequisite essential to design the satellite. In the space environment, it makes satellite survive from extreme hot and cold conditions. In recent years CubeSat mission is developed for many kinds of purpose. Triplet Ionospheric Observatory (TRIO)–CubeSat for Ion, Neutral, Electron, MAgnetic fields (CINEMA) is required to weigh less than 3 kg and operate on minimal 3 W power. In this paper we describe the thermal analysis and control design for TRIO-CINEMA mission. For this thermal analysis, we made a thermal model of the CubeSat with finite element method and NX6.0 TMG software is used to simulate this analysis model. Based on this result, passive thermal control method has been applied to thermal design of CINEMA. In order to get the better conduction between solar panel and chassis, we choose aluminum 6061-T6 for the material property of standoff. We can increase the average tempera\-ture of top and bottom solar panels from -70°C to -40°C and decrease the average temperature of the magnetometer from +93°C to -4°C using black paint on the surface of the chassis, inside of top & bottom solar panels, and magnetometer.
4.
2012.03
서비스 종료(열람 제한)
Yoon, Na-Young, Yoon, Se-Young, Kim, Yong-Ho, Yoon, Ji-Won, Jin, Ho, Seon, Jong-Ho, Chae, Kyu-Sung, Lee, Dong-Hun, Lin, Robert P.
Triplet Ionospheric Observatory (TRIO) CubeSatforIon, Neutral, Electron MAgneticfields (CINEMA) is a CubeSat with the weight 3 kg that will be operated in the orbit conditions of about 800 km altitude and 90° inclination angle, using the S-band and ultra-high frequency (UHF)-band communication frequencies. Regarding the communication antenna loaded on the satellite, the two patch antennas has the downlink function in the S-band, whereas the two whip antennas has the function to receive the command sent by the ground station to the satellite in the UHF-band. The uplink ground station that communicates through the UHF-band with the CINEMA satellite was established at Kyung Hee University. The system is mainly composed of a terminal node controller, a transceiver, and a helical antenna. The gain of the helical antenna established at the Kyung Hee University ground station was 9.8 dBi. The output of the transceiver was set to be 5 W (6.9 dB) for the communication test. Through the far-field test of the established system, it was verified that the Roman characters, figures and symbols were converted into packets and transmitted to the satellite receiver in the communica\-tion speed of 9,600 bps.
5.
2012.03
서비스 종료(열람 제한)
This paper reports the progress of a search for exoplanets with S-type orbits in short-period binary star systems. The se\-lected targets have stellar orbital periods of just a few days. These systems are eclipsing binaries so that exoplanet transits, if planets exist, will be highly likely. We report the results for seven binary star systems.
6.
2012.03
서비스 종료(열람 제한)
Massive binary stars lose mass by two mechanisms: jet-driven mass loss during periods of active mass transfer and by wind-driven mass loss. Beta Lyrae is an eclipsing, semi-detached binary whose state of active mass transfer provides a unique opportunity to study how the evolution of binary systems is affected by jet-driven mass loss. Roche lobe overflow from the primary star feeds the thick accretion disk which almost completely obscures the mass-gaining star. A hot spot predicted to be on the edge of the accretion disk may be the source of beta Lyrae’s bipolar outflows. I present results from spectropolarimetric data taken with the University of Wisconsin’s Half-Wave Spectropolarimeter and the Flower and Cook Observatory’s photoelastic modulating polarimeter instrument which have implications for our current un\-derstanding of the system’s disk geometry. Using broadband polarimetric analysis, I derive new information about the structure of the disk and the presence and location of a hot spot. These results place constraints on the geometrical distri\-bution of material in beta Lyrae and can help quantify the amount of mass lost from massive interacting binary systems during phases of mass transfer and jet-driven mass loss.
7.
2012.03
서비스 종료(열람 제한)
A few high-mass X-ray binaries–consisting of an OB star plus compact companion–have been observed by Fermi andground-based Cerenkov telescopes like High Energy Stereoscopic System (HESS) to be sources of very high energy (VHE;up to 30 TeV) γ-rays. This paper focuses on the prominent γ-ray source, LS 5039, which consists of a massive O6.5V starin a 3.9-day-period, mildly elliptical (e ≈ 0.24) orbit with its companion, assumed here to be an unmagnetized compactobject (e.g., black hole). Using three dimensional smoothed particle hydrodynamics simulations of the Bondi-Hoyle accretionof the O-star wind onto the companion, we find that the orbital phase variation of the accretion follows veryclosely the simple Bondi-Hoyle-Lyttleton (BHL) rate for the local radius and wind speed. Moreover, a simple model,wherein intrinsic emission of γ-rays is assumed to track this accretion rate, reproduces quite well Fermi observations ofthe phase variation of γ-rays in the energy range 0.1-10 GeV. However for the VHE (0.1-30 TeV) radiation observed by theHESS Cerenkov telescope,it is important to account also for photon-photon interactions between the γ-rays and the stellaroptical/UV radiation, which effectively attenuates much of the strong emission near periastron. When this is included,we find that this simple BHL accretion model also quite naturallyfits the HESS light curve, thus making it a strong alternativeto the pulsar-wind-shock models commonly invoked to explain such VHE γ-ray emission in massive-star binaries.
8.
2012.03
서비스 종료(열람 제한)
Binary companions are often invoked to explain the axial and point symmetry seen in the majority of planetary nebulae and proto-planetary nebulae (PPNs). To explore this hypothesis, we have undertaken a long-term (20 year) study of light and velocity variations in PPNs. From the photometric study of 24 PPNs, we find that all vary in brightness, and from a subset of 12 carbon-rich PPNs of F-G spectral type we find periods of 35-155 days, with the cooler having the longer pe\-riods. The variations are seen to be due to pulsation; no photometric evidence for binarity is seen. A radial velocity study of a sub-sample of seven of the brightest of these shows that they all vary with the pulsation periods. Only one shows evidence of a longer-term variation that we tentatively identify as being due to a binary companion. We conclude that the present evidence for the binary nature of these PPNs is meager and that any undetected companions of these PPNs must be of low mass (< 0.25 M ) or long period (> 30 years).
9.
2012.03
서비스 종료(열람 제한)
Observations with milliarsecond resolution using the Navy Optical Interferometer have been obtained for a number of stellar systems which include high-mass binaries, eclipsing binaries, and radio stars. These observations also reveal the previously unseen companions in single-lined spectroscopic binaries via directly measured flux ratios. We will present examples of published and ongoing research efforts of these systems to illustrate how an optical interferometer contrib\-utes to our knowledge of stars, their environment, and companions. These studies include a conclusive revealing of the previously unseen companion in the single-lined binary Φ Herculis, the direct determination of orbital parameters in the wide and close orbits of Algol, and revealing the orbit of β Lyrae with spatially resolved images of the Hα emission.
10.
2012.03
서비스 종료(열람 제한)
Koch, Robert H., Wolf, George W., Hull, Anthony B., Elias, Nicholas M. II, Holenstein, Bruce D., Mitchell, Richard J.
This report describes the inception, development and extensive use over 30 years of elliptical polarimeters at the Uni\-versity of Pennsylvania. The initial Mark I polarimeter design utilized oriented retarder plates and a calcite Foster-Clarke prism as the analyzer. The Mark I polarimeter was used on the Kitt Peak 0.9 m in 1969-70 to accomplish a survey of ap\-proximately 70 objects before the device was relocated to the 0.72 m reflector at the Flower and Cook Observatory. Suc\-cessive generations of automation and improvements included the early-80’s optical redesign to utilize a photoelastic modulated wave plate and an Ithaco lock-in amplifier–the photoelastic modulating polarimeter. The final design in 2000 concluded with a fully remote operable device. The legacy of the polarimetric programs includes studies of close binaries, pulsating hot stars, and luminous late-type variables.
11.
2012.03
서비스 종료(열람 제한)
After a visit by Peter Waddell from the University of Strathclyde, Glasgow, UK in 1991, Robert H. Koch launched a program at the University of Pennsylvania to build lightweight pneumatic membrane mirrors, initially for balloon flight observa\-tions where weight is at a premium. Mirror cells were fabricated from sizes 0.18 m to 1.77 m, and experiments conducted to characterize the mirror figure and stability. Most of the work stopped after Prof. Koch’s retirement in 1996 until 2006 when the authors expressed an interest in building an array of medium-aperture portable telescopes. The program re\-started in earnest at Gravic, Inc. in Malvern, PA in 2008 with Koch using his extensive observational astronomy experience to guide the fabrication of a fully operational 1.07 m membrane mirror telescope with an optical tube assembly weigh\-ing under 45 Kg. Residual wavefront aberrations remediation resulted in Koch and the authors investigating membrane tensioning techniques with different cell designs, active secondary wavefront correction, photometric algorithms for ab\-errated images, and the use of additional lightweight mirror substrates from the Alt-Az Initiative Group, such as foamed glass. The best result for the lightweight mirrors was a point spread function spot size of several arc seconds. A lightweight 1.6 m cast aluminum cell alt-az telescope was subsequently designed by Koch and the authors for prime focus use.
12.
2012.03
서비스 종료(열람 제한)
Nicholas M. Elias II, Stanislav S. Edel, Carol E. Jones, Frances E. Mackay, David Mozurkewich, Anders M. Jorgensen, Henrique R. Schmitt
Optical interferometry and polarimetry have separately provided new insights into stellar astronomy, especially in thefields of fundamental parameters and atmospheric models. We present: scientific justifications for “full-Stokes” opticalinterferometric polarimetry (OIP); updated instrument requirements; preliminary beam combiner designs; polarimeterdesign; end-to-end OIP data reduction; and realistic reimaged full-Stokes models of Be stars with a suitable number oftelescopes plus noise sources. All of this work represents preliminary research to construct an OIP beam combiner.
13.
2012.03
서비스 종료(열람 제한)
There are observational difficulties determining dynamical masses of binary star components in the upper HR diagram both due to the scarcity of massive binary systems and spectral and photometric contamination produced by the strong wind outflows in these systems. We discuss how variable X-ray emission in these systems produced by wind-wind col\-lisions in massive binaries can be used to constrain the system parameters, with application to two important massive binaries, Eta Carinae and WR 140.
