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

• Bulletin of the Korean Space Science Society
• /
• 2001.11a
• /
• pp.63-63
• /
• 2001

• Journal of the Korean Geophysical Society
• /
• v.2 no.2
• /
• pp.135-142
• /
• 1999

Interpretations of 3-component magnetic logging data obtained for a reinforced bar as a model of the line of the magnetic dipoles are conducted using a least squared inversion technique. The length of the bar is 1.12 m, sampling interval is 0.05 m, the distance between the bar and the borehole is 0.3 m, and the top of the bar is fixed at 0 m of depth. The bar is set to be approximately vertical. Magnetic anomalies smoothed with FFT are used as input data for the inversion. For the interpretation of magnetic logging data the depth to the top, the length, the magnetic moment per unit length, the direction of the magnetization (declination and inclination), and the bearing and plunge of the line of magnetic dipoles are left as unknown parameters. The comparison of the results obtained from the individual inversion of the horizontal component or the vertical component of the magnetic anomalies, and those from the simultaneous inversion of horizontal and vertical component of the magnetic anomalies shows that there exist some disagreements between each inversion result. The depth to the bottom of the bar, which is actually 1.12 m, is estimated as 1.18 m, and the inclination of the magnetization is estimated as -76°by simultaneous inversion. The negative value of the inclination indicates that the strength of the remnant magnetization is much greater than that of the induced magnetization, so that the direction of the resultant magnetization points to the top of the bar.

• Journal of the Korean Magnetics Society
• /
• v.9 no.2
• /
• pp.98-103
• /
• 1999

We have studied changes of coercivity $(H_c)$, exchange anisotropy field $(H_{ex})$ and MR ration in glass/Ta/NiFeI/CoI(t)/Cu/CoII(3/4 t)/NiFeII/FeMn spin valve structures by changing Ar pressure and thicknesses of Co layers using DC, RF sputtering methods. We obtained minimum coercivity of 2.8 Oe at 4 mTorr of Ar pressure, exchange anisotropy field of 50.0 Oe at 6 mTorr and 5.3 % of MR ratio at 10 mTorr. Also, we obtained 3.0 Oe of coercivity at 40 $\AA$ of CoI layer, 65.9 Oe at 13 $\AA$ and 4.7 % of MR ratio at 27 $\AA$ and 34 $\AA$ by changing the thicknesses of Co layers.

• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2003.05a
• /
• pp.122-123
• /
• 2003

물리적인 건식 방법으로 소각 및 매립되는 생활계 폐플라스틱에 포함된 이물질을 제거하는 공정을 확립 연구를 수행하였다. 수집 운반되는 생활계 폐플라스틱 시료의 발생 장소, 위치 및 시간에 따라 포함된 이물질 종류가 다르고 수분의 함량에 있어 차이가 많이 있어 투입되는 시료에 대한 일차 이물질 분석이 필요하다. 이물질 분리 공정은 운반 $\rightarrow$ 파쇄 $\rightarrow$ 선별 분리(자력, 와류, 스크린) $\rightarrow$ 저장의 순서로 진행하였으며 파쇄시 흙 종류가 많이 포함된 경우에는 -0.8cm로 파쇄할 경우 효과적이나 일반적으로 -1.2cm 정도로 파쇄하여 이물질을 선별 분리하여도 이물질이 함유량이 3%이하이며, 회수율은 97% 이상이었다.

• Geophysics and Geophysical Exploration
• /
• v.5 no.3
• /
• pp.157-168
• /
• 2002

Improved procedures were implemented in the production of the lithospheric magnetic anomaly map from Magsat satellite magnetometer data of East Asia between $90^{\circ}E-150^{\circ}E$ and $10^{\circ}S-50^{\circ}N$. Procedures included more effective selection of the do·it and dawn tracks, ring current correction, and separation of core field and external field effects. External field reductions included an ionospheric correction and pass-by-pass correlation analysis. Track-line noise effects were reduced by spectral reconstruction of the dusk and dawn data sets. The total field magnetic anomalies were differentially-reduced-to-the-pole to minimize distortion s between satellite magnetic anomalies and their geological sources caused by corefield variations over the study area. Aeromagnetic anomalies were correlated with Magsat magnetic anomalies at the satellite altitude to test the lithospheric veracity of anomalies in these two data sets. The aeromagnetic anomalies were low-pass filtered to eliminate high frequency components that may not be shown at the satellite altitude. Although the two maps have a low CC of 0.243, there are many features that are directly correlated (peak-to-peak and trough-to-trough). The low CC between the two maps was generated by the combination of directly- and inversely-correlative anomaly features between them. It is very difficult to discriminate directly, inversely, and nully correlative features in these two anomaly maps because features are complicatedly correlated due to the depth and superposition of the anomaly sources. In general, the lithospheric magnetic components were recovered successfully from satellite magnetometer observations and correlated well with aeromagnetic anomalies in the study area.

• Journal of the Korean Magnetics Society
• /
• v.3 no.1
• /
• pp.41-47
• /
• 1993

Effects of Ta addition on Co-Cr pependicular magnetic recording media were studied to obtain high perpen-dicular coercivity at lower substrate temperature. For the purpose. magnetic properties and microstructures of Co-Cr-(Ta) films were studied by varying the Cr contents from 17 to 21 at.% and Ta contents for 0 to 3.2 at.%. Effectiveness of Ta addition in increasing perpendicular coercivity was significant for lower Cr content films. The increasement of perpendicular coercivity was more pronounced for the films deposited on $100^{\circ}C$ heated substrate in the case of ${(Co_{83}Cr_{17})}_{98.4}Ta_{1.6}$ composition. The cause of the increase of perpendicular coercivity was considered due to not the grain refinement effects and the improvement of c-axis alignments but increase of Ta and Cr segregation.

• Geophysics and Geophysical Exploration
• /
• v.11 no.4
• /
• pp.343-349
• /
• 2008

We have constructed a car-borne magnetic exploration system, in which a car drags a non-magnetic cart on which a magnetometer is installed. In the total magnetic field measured as a vectorial sum in this system, are included the magnetic field generated by the car itself. This magnetic field, doing the role of a magnetic noise, should be eliminated. For this purpose, we have set up a measurement condition to get the same effect as if we have put the car in one point and thereafter measured the magnetic field around it. In this case, if there is any magnetically anomalous body in the area, we can consider all the remaining magnetic field to have been generated by the car itself, once the geomagnetic field eliminated. We tried to invert the magnetic field considered to have been generated by the car and succeeded to derive the magnetic moment and the direction of the induced and remanent magnetic field of the car respectively. Once the magnetic moment and the direction of the induced and remanent magnetic field have been calculated, the magnetic field generated by them in specific points can be directly and analytically calculated. This result can be used in the future to eliminate the magnetic field generated by the car itself doing the role of a magnetic noise during the procedure of reduction of the measured magnetic exploration data by the car-borne magnetic exploration system.

• Proceedings of the Korean Magnestics Society Conference
• /
• 2016.11a
• /
• pp.136-137
• /
• 2016

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.1
• /
• pp.82-87
• /
• 2002

The attitude determination in LEO Satellite like KOMPSAT is one of the most important issues for Sun-Acquisition. Particularly, in KOMPSAT, the roll axis direction can be determined since the sun sensor gives the information on the Euler angle for pitch and yaw axes in Sun-Acquisition mode. In other words, it is the problem to determine the two unknown axes direction with one axis knowledge. This paper proposes a new effective method for attitude determination of general LEO satellites when one axis information is avilable and proves its usefulness throughout the simulation.