• Journal of Magnetics
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• 제20권1호
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• pp.62-68
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• 2015

This paper presents an experimental technique to accurately separate a permanent magnetic field and an induced one from the total magnetic fields generated by a steel ship, through compensating for the Earth's magnetic field. To achieve this, an Earth's magnetic field simulator was constructed at a non-magnetic laboratory, and the field separation technique was developed, which consisted of five stages. The proposed method was tested with a scaled model ship, and its permanent and induced magnetic fields were successfully extracted from the magnetic field created by the ship. Finally, based on the separated permanent magnetic field data, the permanent magnetization distribution on the hull was predicted by solving an inverse problem. Accordingly, the permanent magnetic fields generated by the ship can easily be calculated at any depth of water.

• 대한원격탐사학회지
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• 제31권4호
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• pp.353-360
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• 2015

Earth's gravity field recovery was improved after the pre-processing upgrade of the Gravity Recovery And Climate Experiments (GRACE) satellite's star trackers. The star tracker measurements were filtered with a tighter low-pass filtering of 0.025Hz cutoff frequency, instead of a nominal filtering of 0.1Hz cutoff frequency. In addition, a jump removal algorithm was applied to remove discontinuities, due to direct Sun and/or Moon interventions, in the star tracker measurements. During the K-Band Ranging (KBR) calibration maneuvers, large attitude variations could be detected concurrently by both of the star trackers and the accelerometer. The misalignment angles of star trackers between the true frame and the normal frame could be determined by comparing measurements from these sensors. In this paper, new Earth' gravity field maps were obtained using above improvement. Based on comparisons to nominal Earth's gravity field maps, the new Earth's gravity field maps were found better than the nominal ones. Among the applied methods, the misalignment calibration of the star trackers had a major impact on the improvement of the new Earth's gravity field maps.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1236-1238
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• 2003

The Earth's total magnetic field was extracted from on board TAM (Three Axis Magnetometer) observations of KOMPSAT-1 satellite between June 19th and 21st, 2000. In the pre-processing, the TAM's telemetry data were transformed from ECI (Earth Centered Inertial frame) to ECEF (Earth Centered Earth Fixed frame) and then to spherical coordination, and self-induced magnetic field by satellite bus itself were removed by using an on-orbit magnetometer data correction method. The 2-D wavenumber correlation filtering and quadrant-swapping method were applied to the pre-processed data in order to eliminate dynamic components and track-line noise, respectively. Then, the spherical harmonic coefficients are calculated from KOMPSAT-1 data. To test the validity of the TAM's geomagnetic field, Danish/NASA/French ${\phi}$rsted satellite's magnetic model and IGRF2000 model were used for statistical comparison. The correlation coefficient between ${\phi}$rsted and TAM is 0.97 and IGRF and TAM is 0.96. It was found that the data from on board magnetometer observations for attitude control of Earth-observing satellites can be used to determinate the Earth's total magnetic field and that they can be efficiently used to upgrade the global geomagnetic field coefficients, such as IGRF by providing new information at various altitudes with better temporal and spatial coverage.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 춘계학술대회 및 창립 30주년 심포지엄(논문집)
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• pp.87-90
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• 2006

지구자장의 주자장과 경년변화에 대한 원통형 지구 조화 모델은, 지구가 지엽적으로 불균형 또는 외부 소스가 없는 정상상태라고 가정하는 경우, 어느 지역의 지구자장 구조와 자장의 세기를 나타낼 수 있다. 이 연구에서는 기초 연구로서 선박용 디지털 컴퍼스를 실제 지구자장에 적용하는 경우의 원통형 조화 모델에 대한 관련 방법과 절차 등을 조사하였다.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2006년도 추계학술발표회
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• pp.131-135
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• 2006

이 연구의 목적은 지구 내부의 동적 코어에서 공간과 시간에 따라서 발생하는 지구 자기장 구조와 그에 따른 경년 자차변화를 모델링하고 연구하는 것이다. 지구의 주 자장과 경년 자차변화에 대한 구형 조화 모델은, 외부 간섭자장이나 내부의 불균일 등이 없다는 가정 하에 안정되고 왜곡되지 않은 지구상 어떠한 위치에서의 지구자장의 구조와 세기를 나타낼 수 있다. 이 연구에서는 선박용 디지털 컴퍼스를 이러한 지구자장 에 적용하는 경우를 고려해 지구의 원 조화 모텔에 대한 실제 적용방법과 절차를 기술하였다.

• 한국지능시스템학회논문지
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• 제16권3호
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• pp.297-302
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• 2006

본 논문에서는 지구자계를 이용하여 3축 자계센서의 수직성분자계를 간편하게 보정할 수 있는 방법과 장치를 제안한다. 자계센서의 출력은 설치각도 및 이득오차에 의한 출력 오프셋을 포함하고 있다. 따라서 자계센서를 사용하기에 앞서 보정이 필요하다. 자계센서의 보정은 무자계 공간에서 이루어져야 하나 지구자계를 이용하면 간단하게 자계센서의 출력 오프셋을 보정할 수 있다. 그리고 보정을 위한 장치를 설계하였다. 제안하는 방법과 장치는 실험을 통하여 실용성을 검증하였다.

• Journal of Astronomy and Space Sciences
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• 제17권2호
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• pp.317-328
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• 2000

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.

• 한국자기학회지
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• 제2권2호
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• pp.156-162
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• 1992

저자장방법으로 양성자 자기회전비율을 측정할 때, 지자장을 상쇄시켜 무자장 실험공간을 형성시킬 필요가 있다. 이를 위해 일정한 자장성분은 헬름홀쯔코일에 흐르는 정전류에 의하여 상쇄 되고, 미소변화 자장은 폐회로를 구성하는 궤환장치에 의해 자동적으로 상쇄되는 지자장 상쇄장치 를 설계하였다. 지자장성분을 상쇄하기 위해 코일상수가 같은 대형 및 소형 3축 헬름홀쯔코일과 미 소변화 자장 상쇄용 궤환증폭기를 제작하였다. 제작된 시스템을 사용하여 일반실험실 내에서 예비 실험을 한 결과 수십 ${\mu}T$ 의 일정한 자장성분과 ${\pm}100nT$ 의 미소변화 자장을 상쇄하여 잔류자 장이 ${\pm}10nT$ 이하인 공간을 형성하였다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.242-242
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• 2002

The Earth's magnetic field acquired from KOMPSAT-1's TAM (Three-Axis Magnetometer) between June 19th and 21st 2000 was analyzed. The TAM, one of the KOMPSAT-1's Attitude and Orbit Control Subsystems, plays an important role in determining and controlling the satellite's attitude. This also can provide new insight on the Earth's magnetic field. By transforming the satellite coordinate from ECI to ECEF, spherical coordinate of total magnetic field was achieved. These data were grouped into dusk (ascending) and dawn (descending) data sets, based on their local magnetic times. This partitioning is essential for performing 1-D WCA (Wavenumber Correlation Analysis). Also, this enhances the perception of external fields in the Kompsat-1's TAM magnetic maps that were compiled according to different local. The dusk and dawn data are processed independently and then merged to produce a total field magnetic anomaly map. To extract static and dynamic components, the 1-D and 2-D WCAs were applied to the sub-parallel neighboring tracks and dawn-dusk data sets. The static components were compared with the IGRF, the global spherical harmonic magnetic field model. The static and dynamic components were analyzed in terms of corefield, external, and crustal signals based on their origins.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.36-40
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• 2003

The considered satellite is supposed to operate in the earth-point mode and sun-point mode in accordance with the mission requirements. The magnetic field correction is based on the orbit geometry using a set of measured magnetic field data from the three-axis-magnetometer and its algorithm excludes the earth’s magnetic field model. Moreover, the usefulness of the proposed method is investigated throughout the simulation of KOMPSAT-1.