Ionospheric and hardware fluctuations of the optical path during radio occultation sounding of the earth’s atmosphere in the COSMIC experiment
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- Es’kin, G.I. Radiophys Quantum El (2012) 55: 176. doi:10.1007/s11141-012-9358-0
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Ionospheric and hardware fluctuations of optical paths are the most significant sources of errors in determination of the parameters of the neutral atmosphere using the radio occultation method at altitudes above 8 km. The paper presents a spectral analysis of the fluctuations in the optical path during radio occultation measurements in two channels of the GPS system for the perigee altitudes of probing beams in the range from 80 to 100 km, where the contribution of the neutral atmosphere is negligibly small. For analysis, a data set of 300 measurements made during the COSMIC experiment was used. The spectral analysis revealed the maximum cross-correlation of the fluctuations in two channels at a spatial frequency of 2.5 rad/km. Weaker correlation for lower spatial frequencies is determined by hardware noise. Weaker correlation for higher spatial frequencies is determined by the effects of diffraction by small-scale ionospheric irregularities.