• Title/Summary/Keyword: Space radiation

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Development of High Energy Particle Detector for the Study of Space Radiation Storm

  • Jo, Gyeong-Bok;Sohn, Jongdae;Choi, Cheong Rim;Yi, Yu;Min, Kyoung-Wook;Kang, Suk-Bin;Na, Go Woon;Shin, Goo-Hwan
    • Journal of Astronomy and Space Sciences
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    • v.31 no.3
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    • pp.277-283
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    • 2014
  • Next Generation Small Satellite-1 (NEXTSat-1) is scheduled to launch in 2017 and Instruments for the Study of Space Storm (ISSS) is planned to be onboard the NEXTSat-1. High Energy Particle Detector (HEPD) is one of the equipment comprising ISSS and the main objective of HEPD is to measure the high energy particles streaming into the Earth radiation belt during the event of a space storm, especially, electrons and protons, to obtain the flux information of those particles. For the design of HEPD, the Geometrical Factor was calculated to be 0.05 to be consistent with the targets of measurement and the structure of telescope with field of view of $33.4^{\circ}$ was designed using this factor. In order to decide the thickness of the detector sensor and the classification of the detection channels, a simulation was performed using GEANT4. Based on the simulation results, two silicon detectors with 1 mm thickness were selected and the aluminum foil of 0.05 mm is placed right in front of the silicon detectors to shield low energy particles. The detection channels are divided into an electron channel and two proton channels based on the measured LET of the particle. If the measured LET is less than 0.8 MeV, the particle belongs to the electron channel, otherwise it belongs to proton channels. HEPD is installed in the direction of $0^{\circ}$, $45^{\circ}$, $90^{\circ}$ against the along-track of a satellite to enable the efficient measurement of high energy particles. HEPD detects electrons with the energy of 0.1 MeV to several MeV and protons with the energy of more than a few MeV. Thus, the study on the dynamic mechanism of these particles in the Earth radiation belt will be performed.

Forbush Decreases Observed by the LRO/CRaTER

  • Sohn, Jongdae;Oh, Suyeon;Yi, Yu;Kim, Eojin;Lee, Joo-Hee;Spence, Harlan E.
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.120.1-120.1
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    • 2012
  • The Lunar Reconnaissance Orbiter (LRO) launched on June 16, 2009 has six experiments including of the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) onboard. The CRaTER instrument characterizes the radiation environment to be experienced by humans during future lunar missions. The CRaTER instrument measures the effects of ionizing energy loss in matter specifically in silicon solid-state detectors due to penetrating solar energetic protons (SEP) and galactic cosmic rays (GCRs) after interactions with tissue-equivalent plastic (TEP), a synthetic analog of human tissue. The CRaTER instrument houses a compact and highly precise microdosimeter. It measures dose rates below one micro-Rad/sec in silicon in lunar radiation environment. Forbush decrease (FD) event is the sudden decrease of GCR flux. We use the data of cosmic ray and dose rates observed by the CRaTER instrument. We also use the CME list of STEREO SECCHI inner, outer coronagraph and the interplanetary CME data of the ACE/MAG instrument.We examine the origins and the characteristics of the FD-like events in lunar radiation environment. We also compare these events with the FD events on the Earth. We find that whenever the FD events are recorded at ground Neutron Monitor stations, the FD-like events also occur on the lunar environments. The flux variation amplitude of FD-like events on the Moon is approximately two times larger than that of FD events on the Earth. We compare time profiles of GCR flux with of the dose rate of FD-like events in the lunar environment. We figure out that the distinct FD-like events correspond to dose rate events in the CRaTER on lunar environment during the event period.

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A Study on the Analysis of the Configuration and Properties of University Campus Cores through Space Syntax (공간구문론을 이용한 대학교 캠퍼스 코어의 공간구조 유형 및 특성 분석)

  • Lee, Dong-Joo;Ko, Eun-Hyung
    • Journal of the Korean Institute of Educational Facilities
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    • v.16 no.6
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    • pp.13-20
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    • 2009
  • The purpose of this study is to analyze the configuration and properties of university campus cores for systematic approach and planning through space syntax based on master plans of 55 universities in Korea. The results of this study showed that: first, the campus cores were classified into 10 types through axial map analysis. They were '一 type', '二 type', 'ㄱ type', 'T type', '+ type', 'radiation type', 'grid type', 'polygon type', 'tree structure type' and 'combination type'.(table 7) The frequency of '一 type' was the highest by 27.2%, and 'radiation type' was the next by 14.5%; second, the integration value was 2.03(+ type), te90(grid type), te75(ㄱ type), te74(一 type), te67(二 type), te63(T type), te46(polygon type), te347(tree structure type) and te343(radiation type).(table 9) We could categorize the 'radiation type' and the 'tree structure type' as the first group, the 'polygon type' as the second group, the 'T type', the '二 type', the '一 type', and the 'ㄱ type' as the third group, the 'grid type' as the fourth group, the '+ type' as the fifth group; third, cases that the integration value of access road was very low(58.2%) was much more frequent than that of very high(32.7%); fourth, the most important space in the campus core were as follows: library and media center(18.1%), administration buildings and headquarters(15.7%), student center(15.7%), lecturing building(13.9%), streets and squares(13.3%).

Prediction Model of the Outer Radiation Belt Developed by Chungbuk National University

  • Shin, Dae-Kyu;Lee, Dae-Young;Kim, Jin-Hee;Cho, Jung-Hee
    • Journal of Astronomy and Space Sciences
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    • v.31 no.4
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    • pp.303-309
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    • 2014
  • The Earth's outer radiation belt often suffers from drastic changes in the electron fluxes. Since the electrons can be a potential threat to satellites, efforts have long been made to model and predict electron flux variations. In this paper, we describe a prediction model for the outer belt electrons that we have recently developed at Chungbuk National University. The model is based on a one-dimensional radial diffusion equation with observationally determined specifications of a few major ingredients in the following way. First, the boundary condition of the outer edge of the outer belt is specified by empirical functions that we determine using the THEMIS satellite observations of energetic electrons near the boundary. Second, the plasmapause locations are specified by empirical functions that we determine using the electron density data of THEMIS. Third, the model incorporates the local acceleration effect by chorus waves into the one-dimensional radial diffusion equation. We determine this chorus acceleration effect by first obtaining an empirical formula of chorus intensity as a function of drift shell parameter $L^*$, incorporating it as a source term in the one-dimensional diffusion equation, and lastly calibrating the term to best agree with observations of a certain interval. We present a comparison of the model run results with and without the chorus acceleration effect, demonstrating that the chorus effect has been incorporated into the model to a reasonable degree.

THE ANALYSIS ON SPACE RADIATION ENVIRONMENT AND EFFECT OF THE KOMPSAT-2 SPACECRAFT(II): SINGLE EVENT EFFECT (아리랑 2호의 방사능 환경 및 영향에 관한 분석(II)- SINGLE EVENT 영향 중심으로 -)

  • 백명진;김대영;김학정
    • Journal of Astronomy and Space Sciences
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    • v.18 no.2
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    • pp.163-173
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    • 2001
  • In this paper, space radiation environment and single event effect(SEE) have been analyzed for the KOMPSAT-2 operational orbit. As spacecraft external and internal space environment, trapped proton, SEP(solar energetic particle) and GCR(galactic cosmic ray) high energy Protons and heavy ions spectrums are analyzed. Finally, SEU and SEL rate prediction has been performed for the Intel 80386 microprocessor CPU that is planned to be used in the KOMPSAT-2. As the estimation results, under nominal operational condition, it is predicted that trapped proton and high energetic proton induced SBU effect will not occur. But, it is predicted that heavy ion induced SEU can occur several times during KOMPSAT-2 3-year mission operation. KOMPSAT-2 has been implementing system level design to mitigate SEU occurrence using processor CPU error detection function of the on-board flight software.

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