• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.42.3-43
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• 2009

Triplets of identical cubesats will be built to carry out the following scientific objectives: i) multi-observations of ionospheric ENA (Energetic Neutral Atom) imaging, ii) ionospheric signature of suprathermal electrons and ions associated with auroral acceleration as well as electron microbursts, and iii) complementary measurements of magnetic fields for particle data. Each satellite, a cubesat for ion, neutral, electron, and magnetic fields (CINEMA), is equipped with a suprathermal electron, ion, neutral (STEIN) instrument and a 3-axis magnetometer of magnetoresistive sensors. TRIO is developed by three institutes: i) two CINEMA by Kyung Hee University (KHU) under the WCU program, ii) one CINEMA by UC Berkeley under the NSF support, and iii) three magnetometers by Imperial College, respectively. Multi-spacecraft observations in the STEIN instruments will provide i) stereo ENA imaging with a wide angle in local times, which are sensitive to the evolution of ring current phase space distributions, ii) suprathermal electron measurements with narrow spacings, which reveal the differential signature of accelerated electrons driven by Alfven waves and/or double layer formation in the ionosphere between the acceleration region and the aurora, and iii) suprathermal ion precipitation when the storm-time ring current appears. In addition, multi-spacecraft magnetic field measurements in low earth orbits will allow the tracking of the phase fronts of ULF waves, FTEs, and quasi-periodic reconnection events between ground-based magnetometer data and upstream satellite data.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.40-45
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• 2022

The electrical/thermal stabilities and magnetic field controllability of a no-insulation (NI) high-temperature superconducting magnet are characterized by contact resistance between turn-to-turn layers, and the contact resistance characteristics are determined by properties of conductor surface and winding tension. In order to accurately predict the electromagnetic characteristics of the NI coil in a design stage, it is necessary to control the contact resistance characteristics within the design target parameters. In this paper, the contact resistance and critical current characteristics of a rare-earth barium copper oxide (REBCO) conductor were measured to analyze the effects of surface treatment conditions (roughness and oxidation level) of the copper stabilizer layer in REBCO conductor. The test samples with different surface roughness and oxidation levels were fabricated and conductor surface analysis was performed using scanning electron microscope, alpha step surface profiler and energy dispersive X-ray spectroscopy. Moreover, the contact resistance and critical current characteristics of the samples were measured using the four-terminal method in a liquid nitrogen impregnated cooling environment. Compared with as-received REBCO conductor sample, the contact resistance values of the REBCO conductors, which were post-treated by the scratch and oxidation of the surface of the copper stabilizer layer, tended to increase, and the critical current values were decreased under certain roughness and oxidation conditions.

• Economic and Environmental Geology
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• v.45 no.4
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• pp.377-384
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• 2012

The main field component of the Earth's magnetic field was modeled from the tri-axial magnetometer onboard KOrean MultiPurpose SATellite-II (KOMPSAT-II) for the purpose of satellite attitude control. The model computed by the KOMPSAT-II magnetometer measurement data is compared with the International Geomagnetic Reference Field (IGRF) model of a degree of up to 13 in spherical harmonic coefficients. The previous study with KOMPSAT-I (Kim et al. 2004) indicated a good correlation of power spectrum of spherical harmonic coefficients with respect to the degree up to 5. This study, however, showed an agreement of the degree up to 8-9 of the coefficient power spectrum and a discrepancy between degrees 10 and 13. We have concluded that relevant data selection process, removal of the external field from the data in the high latitude region, an accuracy of the magnetometer all play an important role in finding a coherence with the IGRF model. This study will be extended to the secular variation model of geomagnetism if longer-period data become available.

• Geophysics and Geophysical Exploration
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• v.20 no.1
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• pp.1-11
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• 2017

In order to improve the accuracy of microseismic epicenter location through the inversion techniques using P and S wave first arrivals, field experiments of microseismic monitoring were performed using borehole 3-component geophones. The direction of epicenter was estimated from the hodograms of P-wave first arrivals through the weight drop experiments in which the $\times$ component of 3-component geophone was aligned to the magnetic north. The picking of S wave first arrival was possible in the polarization filtered data even if S waves are difficult to be identified in raw data. The inversion technique using only P wave first arrival times can often converge to the local minimum when the initial values for epicenter are largely apart from the true epicenter, so that the correct solution can not be found. To solve this problem, the epicenter determination method using differences between P and S wave arrival times was used to estimate proper initial values of epicenter. The inversion result using only P-wave first arrival times which started from the estimated initial values showed the improved accuracy of the epicenter location.

• Journal of Astronomy and Space Sciences
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• v.20 no.1
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• pp.29-42
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• 2003

The KSR-3 magnetometers consist of the fluxgate magnetometer (MAG/AIM) for acquiring the rocket flight attitude information, and the search-coil magnetometer (MAG/SIM) for the observation of the Earth's magnetic fluctuations. The position (latitude, longitude, and height) and flight condition (the transformation angle) of the rocket is measured after the data based on these two magnetometers are compared with IGRF The gap in the vector of magnetic field between the position of the launching point and an impact point is taken into account in data reduction. Angular variation of pitch, yaw, and roll can be researched when the data is applied to the coordinate system of the rocket.

• The Bulletin of The Korean Astronomical Society
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• v.39 no.2
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• pp.106-106
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• 2014

SIGMA (Scientific cubesat with Instrument for Global Magnetic field and rAdiation)는 근 지구공간에서 우주방사선량 측정과 자기장 변화 검출의 과학적 목적과 교육적 목적을 가지고 개발하고 있는 초소형 큐브위성이다. $100mm{\times}100mm{\times}340.5mm$의 크기로 약 3.6 kg의 무게를 가지며, 탑재체는 방사선에 대하여 인체와 동일한 산란 흡수 특성을 가진 Tissue Equivalent Proportional Counter (TEPC)와 자기장 측정을 위한 Magnetometer (Mag)이다. 위성체는 구조계, 자세제어계, 전력계, 명령 및 데이터처리계, 통신계로 구성되어있다. 구조계는 위성의 뼈대인 Chassis와 Mag deployer로 이루어져있고, 위성의 안정적인 자세유지를 목적으로 Attitude Control System (ACS) Board와 Torque Coil이 자세제어계로 구성된다. 전력의 생산과 공급 및 충전은 태양전지판과 Electrical Power System (EPS), 리튬 배터리로 구성된 전력계에서 이뤄지며, 명령 및 데이터처리계는 On Board Computer (OBC)와 Instrument Interface board (IIB)를 중심으로 서브시스템의 명령체계와 데이터처리를 다룬다. 통신계는 Uplink인 VHF 안테나와 Downlink인 UHF, S-band 안테나로 구성되며 지상과 명령을 송수신한다. SIGMA는 타임인터럽트 기능을 활용한 Flight Software (FSW)로 운용되며 임무에 따른 6가지 모드의 시나리오로 위성을 운용한다. 이에 SIGMA의 개발과 테스트 결과를 소개한다. 본 큐브위성 개발기술을 바탕으로 향후 천문관측용 위성에도 활용할 예정이다.

• Economic and Environmental Geology
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• v.34 no.1
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• pp.119-131
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• 2001

A mean characteristic remanent magnetization was obtained for the first time in Korea from volcanic and pyroclastic sedimentary rocks distributed in Haenam Area, located in southwestern part of the Korean Peninsula. The age of the prevailing rocks in this area belongs mostly to Late Cretaceous, with a few exceptions of Early Cretaceous, mainly based on K/Ar whole rock age dating. Characteristic remanent magnetizations of these have both normal and reverse polarities with antipodal direction, which were interpreted to be the primary remanent magnetizations obtained by the ambient Earth's magnetic field at the time of formation of the concerned rocks. The source magnetic minerals of the remanent magnetization has been identified as magnetite. The mean direction of characteristic remanent magnetization obtained from the Late Cretaceous rocks in this study is Dm/Im=21.4 supper(o)/57.1 supper(o) (${\alpha}_{95}=13.4^{\circ}$, k=350.0). The paleomagnetic pole position calculated from this result for the Late Cretaceous, is $72.5^{\circ}N/199.9^{\circ}E$ (dp/dm= $14.2^{\circ}/19.5^{\circ}E$), which matches well with those of 80 Ma ($76.2^{\circ}N/198.9^{\circ}E$) and 90 Ma ($76.2^{\circ}N/200.1^{\circ}E$) of the Eurasian Continent's APWP (Apparent Polar Wander Path). This result strongly indicates that the studied area, belonging to the Eurasian Continent, have suffered very little geotectonic movement after the Late Cretaceous. The deflection of declination of remanence from Early Cretaceous rocks in the study area may indicate that the micro-block was counterclockwisely rotated with vertical axis between the late of Early Cretaceous and the early of Late Cretaceous.

• Geophysics and Geophysical Exploration
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• v.15 no.2
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• pp.51-56
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• 2012

One of the most critical and essential procedures in the interpretation of gravity and magnetic data is to separate the anomaly due to the specific geologic structure from the summation of effects from a broad variety of geologic sources, especially those of different depths. Separation of the residual anomaly from the regional field is the most simple case of the vertical separation. If the anomaly due to a layer of specific depth can be separated or the depth of the separated layer can be quantitatively determined, it may deserve the separation-sounding. We suggest a wavelength filter whose cutoff frequency is determined by log-power spectrum analysis, as a separation-sounding filter. We applied this filter both to synthetic and real gravity data acquired at Heunghae area, and compared the results with those of Jacobsen's upward continuation filter. These showed that the proposed separation-sounding filter could be a useful tool for interpretation of the vertical geologic structure by stripping the gravity effects of geologic sources down to the desired depth.

• Publications of The Korean Astronomical Society
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• v.15 no.spc2
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• pp.45-52
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• 2000

Four plasma instruments are currently under development for KAISTSAT-4 (K-4) which is scheduled for launch in 2002. They are the Solid-State Telescope, Electro-Static Analyzer, Langmuir Probe, and the Scientific Magnetometer, that will respectively allow in-situ detection of high energy and low energy components of auroral particles, ionospheric thermal electrons, and magnetic field disturbances. These instruments, together with the Far-ultraviolet IMaging Spectrograph, will provide micro-scale physics of Earth's polar ionosphere with detailed spectral information that has not been previously achieved with other space missions. In this paper, we review the concept of the four space plasma instruments as well as the anticipated results from the instruments.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.6
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• pp.137-141
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• 2022

The method of estimating the azimuth by measuring the geomagnetism has been used for a very long time. However, there are many cases where an error occurs in the estimated azimuth due to disturbances in the earth's magnetic field due to metal structures inside and outside the room. Although many studies have been conducted to correct this, there is a limit to reducing the error. In this paper, we propose a method of estimating the azimuth by applying the measured geomagnetic sensor data to the neural network of the LSTM structure. Data preprocessing is very important for learning a neural network. In this paper, data is collected using the built-in acceleration sensor, gyro sensor, and geomagnetic sensor in the smartphone, and the geomagnetic sensor data is uniformly sampled using EKF. As a result, an average azimuth estimation error of 0.9 degrees was obtained using four hidden layers.