• Korean Journal of Remote Sensing
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• v.25 no.5
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• pp.391-398
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• 2009

Variations of mean ionospheric spatial gradient over Korea are analyzed in order to support GNSS (Global Navigation Satellite System) augmentation systems and integrity monitering systems. A software for analyzing the ionospheric spatial gradient is developed using an ionospheric plate model. Daily and annual variations of ionospheric delay and spatial gradient are analyzed using GPS data in 2003 and 2005 respectively. The ionospheric delays and spatial gradients in 2003 were larger than 2005. Also, the south-north gradient, about -1.0mm/km, is nearly two times larger than the east-west gradient. The annual ionospheric spatial gradients over Korea is varied within 2mm/km.

• Journal of Astronomy and Space Sciences
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• v.34 no.4
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• pp.343-352
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• 2017

A space plasma facility has been operated with a back-diffusion-type plasma source installed in a mid-sized vacuum chamber with a diameter of ~1.5 m located in Satellite Technology Research Center (SaTReC), Korea Advanced Institute of Science and Technology (KAIST). To generate plasma with a temperature and density similar to the ionospheric plasma, nickel wires coated with carbonate solution were used as filaments that emit thermal electrons, and the accelerated thermal electrons emitted from the heated wires collide with the neutral gas to form plasma inside the chamber. By using a disk-type Langmuir probe installed inside the vacuum chamber, the generation of plasma similar to the space environment was validated. The characteristics of the plasma according to the grid and plate anode voltages were investigated. The grid voltage of the plasma source is realized as a suitable parameter for manipulating the electron density, while the plate voltage is suitable for adjusting the electron temperature. A simple physical model based on the collision cross-section of electron impact on nitrogen molecule was established to explain the plasma generation mechanism.