• Title/Summary/Keyword: Space time series data

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Time-series Spectroscopy of the Pulsating Eclipsing Binaries using BOES

  • Koo, Jae-Rim;Lee, Jae Woo;Hong, Kyeongsoo;Kim, Seung-Lee;Lee, Chung-Uk;Park, Jang-Ho
    • The Bulletin of The Korean Astronomical Society
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    • v.41 no.1
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    • pp.60.2-60.2
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    • 2016
  • Oscillating Algol-type eclipsing binaries (oEA) are very interesting objects that have three observational features of eclipse, pulsation, and mass transfer. Direct measurement of their masses and radii from the double-lined radial velocity (RV) data and photometric light curves would be the most essential for understanding their evolutionary process and for performing the asteroseismological study. However, only handful oEA stars were studied in detail. To advance this subject, we have been obtaining high-resolution spectra for several oEA stars using Bohyunsan Optical Echelle Spectrograph (BOES). In this presentation, we present our results such as the accurate absolute parameters and evolutionary states for each object, based on the simultaneous analyses of the light and RV curves.

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Orbit Determination from Tracking Data of Artificial Satellite Using the Method of Differential Correction (인공위성 추적자료의 미분보정에 의한 궤도결정)

  • 이병선;조중현;박상영;최규홍;김천휘
    • Journal of Astronomy and Space Sciences
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    • v.5 no.1
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    • pp.31-43
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    • 1988
  • The differential correction process determining osculating orbital elements as correct as possible at a given instant of time from tracking data of artificial satellite was accomplished. Preliminary orbital elements were used as an initial value of the differential correction procedure and iterated until the residual of real observation (O) and computed observation(C) was minimized. Tracking satellite was NOAA-9 or TIROS-N series. Two types of tracking data were prediction data precomputed from mean orbital elements of TBUS and real data obtained from tracking 1.70 GHz HRPT signal of NOAA-9 using 5 meter auto-track antenna in Radio Research Laboratory. Accrding to thacking data either Gause method or Herrick-Gibbs method was applied to preliminary orbit determination. In the differential correction stage we used both of the Escobal(1975)'s analytical method and numerical method using f, g series for the comparision. The results between analytical and numerical ones are nearly consistent. And the differentially corrected orbit converged to the same value in spite of the differences between preliminary orbits of each time span.

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Comparison on the Time series of Housing Viewpoint of University Student (대학생 주거관의 시계열적 비교)

Combined GPS/GLONASS Relative Receiver DCB Estimation Using the LSQ Method and Ionospheric TEC Changes over South Korea

  • Choi, Byung-Kyu;Yoon, Ha Su;Lee, Sang Jeong
    • Journal of Positioning, Navigation, and Timing
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    • v.7 no.3
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    • pp.175-181
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    • 2018
  • The use of dual-frequency measurements from the Global Navigation Satellite System (GNSS) enables us to observe precise ionospheric total electron content (TEC). Currently, many GNSS reference stations in South Korea provide both GPS and GLONASS data. In the present study, we estimated the grid-based TEC values and relative receiver differential code biases (DCB) from a GNSS network operated by the Korea Astronomy and Space Science Institute. In addition, we compared the diurnal variations in a TEC time series from solutions of the GPS only, the GLONASS only, and combined GPS/GLONASS processing. A significant difference between the GPS only TEC and combined GPS/GLONASS TEC at a specific grid point over South Korea appeared near the solar terminator. It is noted that GLONASS measurements can contribute to observing a variation in ionospheric TEC over high latitude regions.

Toward accurate synchronic magnetic field maps using solar frontside and AI-generated farside data

  • Jeong, Hyun-Jin;Moon, Yong-Jae;Park, Eunsu
    • The Bulletin of The Korean Astronomical Society
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    • v.46 no.1
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    • pp.41.3-42
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    • 2021
  • Conventional global magnetic field maps, such as daily updated synoptic maps, have been constructed by merging together a series of observations from the Earth's viewing direction taken over a 27-day solar rotation period to represent the full surface of the Sun. It has limitations to predict real-time farside magnetic fields, especially for rapid changes in magnetic fields by flux emergence or disappearance. Here, we construct accurate synchronic magnetic field maps using frontside and AI-generated farside data. To generate the farside data, we train and evaluate our deep learning model with frontside SDO observations. We use an improved version of Pix2PixHD with a new objective function and a new configuration of the model input data. We compute correlation coefficients between real magnetograms and AI-generated ones for test data sets. Then we demonstrate that our model better generate magnetic field distributions than before. We compare AI-generated farside data with those predicted by the magnetic flux transport model. Finally, we assimilate our AI-generated farside magnetograms into the flux transport model and show several successive global magnetic field data from our new methodology.

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A Study on the Characteristics of Change by Observation Area which changes as the observation time passes in Interior Space (실내공간에서 주시시간의 경과에 따른 구역별 주시특성에 관한 연구)

  • Kim, Jong-Ha;Ban, Young-Sun
    • Korean Institute of Interior Design Journal
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    • v.21 no.2
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    • pp.84-91
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    • 2012
  • The total data of observing interior space was divided into a few time frames for analysis. If we can understand the changing process of observation degree as the observation time passes, we will be able to analyse the characteristic and process of information obtainment in the case of space observation. For this purpose, the observation time was parted into 30 second units and the changing characteristic by time frame and observation area was analysed. The conclusion derived from this study is as the following: First, analysis of observation frequency and time on the basis of the average data of each subject showed that the observation time increased compared with the subject's frequency and the overall trend but that it was difficult for me to think there was a certain trend in the observation time of each subject. However, when I examined the time change by using the trend line which is a dynamic average line representing the observation time from the subjects as the trend element of time series, I could see the trend that the subject's observation time increased at a fixed rate as the frequency increased. Second, when I compared and analysed the average observation area at Area I set up by the time of 30 second unit and the observation area of Area I from the all data, I could see that the former had more degree of concentration at Area I. This analysis enabled me to get the degree of concentration on the observed area every time, and accordingly I could also see that when the data of intensive observation by time frame is analysed, the degree of concentration is dispersed for the subjects to observe very intensively or the area with overlapping observations each time frame can be seen as Area I out of the entire observation data. Third, when I analysed the observation characteristics by time frame at the 6 areas divided at 30 second unit at the rate of the number to the time of observation areas, I could see that as the observation time passed while the number of the observation areas defined as decreased the observation time increased, which means that when the area numbers decreases the area intensively observed by the subjects decreases as the time passes. In spit of that, the increase of time can be interpreted as more intensive observation of a specific area.

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Monitoring Time-Series Subsidence Observation in Incheon Using X-Band COSMO-SkyMed Synthetic Aperture Radar

  • Sang-Hoon Hong
    • Korean Journal of Remote Sensing
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    • v.40 no.2
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    • pp.141-150
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    • 2024
  • Ground subsidence in urban areas is mainly caused by anthropogenic factors such as excessive groundwater extraction and underground infrastructure development in the subsurface composed of soft materials. Global Navigation Satellite System data with high temporal resolution have been widely used to measure surface displacements accurately. However, these point-based terrestrial measurements with the low spatial resolution are somewhat limited in observing two-dimensional continuous surface displacements over large areas. The synthetic aperture radar interferometry (InSAR) technique can construct relatively high spatial resolution surface displacement information with accuracy ranging from millimeters to centimeters. Although constellation operations of SAR satellites have improved the revisit cycle, the temporal resolution of space-based observations is still low compared to in-situ observations. In this study, we evaluate the extraction of a time-series of surface displacement in Incheon Metropolitan City, South Korea, using the small baseline subset technique implemented using the commercial software, Gamma. For this purpose, 24 COSMO-SkyMed X-band SAR observations were collected from July 12, 2011, to August 27, 2012. The time-series surface displacement results were improved by reducing random phase noise, correcting residual phase due to satellite orbit errors, and mitigating nonlinear atmospheric phase artifacts. The perpendicular baseline of the collected COSMO-SkyMed SAR images was set to approximately 2-300 m. The surface displacement related to the ground subsidence was detected approximately 1 cm annually around a few Incheon Subway Line 2 route stations. The sufficient coherence indicates that the satellite orbit has been precisely managed for the interferometric processing.

Short Periodicities in Latitudinal Variation of Sunspots

  • Kim, Bang-Yeop;Chang, Heon-Young
    • Journal of Astronomy and Space Sciences
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    • v.28 no.2
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    • pp.103-108
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    • 2011
  • The latitudinal variation of sunspots appearing during the period from 1874 to 2009 has been studied in terms of centerof-latitude (COL). The butterfly diagram has been used to study the evolution of the magnetic field and the dynamics at the bottom of the solar convection zone. Short-term periodicities have been of particular interest, in that they are somehow related to the structure and dynamics of the solar interior. We thus have focused our investigation on shortterm periodicities. We first calculated COL by averaging the latitude of sunspots with the weight function in area. Then, we analyzed the time series of COL using the wavelet transform technique. We found that a periodicity of ~5 years is the most dominant feature in the time series of COL, with the exception of the ~11 year solar cycle itself. This periodicity can be easily understood by considering small humps between the minima in the area-weighted butterfly diagram. However, we find that periodicities of ~1.3 (0.064), ~1.5 (0.056), or ~1.8 (0.046) years ($\frac{1}{month}$), month ), which have been previously suggested as evidence of links between the changing structure of the sunspot zone and the tachocline rotation rate oscillations, are insignificant and inconsistent. We therefore conclude that the only existing short-term periodicity is of ~5 years, and that periodicities of ~1.3, ~1.5, or ~1.8 years are likely to be artifacts due to random noise of small sunspots.

A Geometric Compression Method Using Dominant Points for Transmission to LEO Satellites

  • Ko, Kwang Hee;Ahn, Hyo-Sung;Wang, Semyung;Choi, Sujin;Jung, Okchul;Chung, Daewon;Park, Hyungjun
    • International Journal of Aeronautical and Space Sciences
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    • v.17 no.4
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    • pp.622-630
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    • 2016
  • In the operation of a low earth orbit satellite, a series of antenna commands are transmitted from a ground station to the satellite within a visibility window (i.e., the time period for which an antenna of the satellite is visible from the station) and executed to control the antenna. The window is a limited resource where all data transmission is carried out. Therefore, minimizing the transmission time for the antenna commands by reducing the data size is necessary in order to provide more time for the transmission of other data. In this paper, we propose a geometric compression method based on B-spline curve fitting using dominant points in order to compactly represent the antenna commands. We transform the problem of command size reduction into a geometric problem that is relatively easier to deal with. The command data are interpreted as points in a 2D space. The geometric properties of the data distribution are considered to determine the optimal parameters for a curve approximating the data with sufficient accuracy. Experimental results demonstrate that the proposed method is superior to conventional methods currently used in practice.

OSCULATING VERSUS INTERSECTING CIRCLES IN SPACE-BASED MICROLENS PARALLAX DEGENERACIES

  • Gould, Andrew
    • Journal of The Korean Astronomical Society
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    • v.52 no.4
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    • pp.121-131
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    • 2019
  • I investigate the origin of arc degeneracies in satellite microlens parallax ${\pi}_E$ measurements with only late time data, e.g., t > $t_0+t_E$ as seen from the satellite. I show that these are due to partial overlap of a series of osculating, exactly circular, degeneracies in the ${\pi}_E$ plane, each from a single measurement. In events with somewhat earlier data, these long arcs break up into two arclets, or (with even earlier data) two points, because these earlier measurements give rise to intersecting rather than osculating circles. The two arclets (or points) then constitute one pair of degeneracies in the well-known four-fold degeneracy of space-based microlens parallax. Using this framework of intersecting circles, I show that next-generation microlens satellite experiments could yield good ${\pi}_E$ determinations with only about five measurements per event, i.e., about 30 observations per day to monitor 1500 events per year. This could plausibly be done with a small (hence cheap, in the spirit of Gould & Yee 2012) satellite telescope, e.g., 20 cm.