A Mie lidar system with vertical scanning and long-range detection capabilities wa used for the study of atmospheric conditions in the lower troposphere. Based on the multiangle method and the assumption of horizontal atmospheric homogeneity, the optical depth and the atmospheric extinction are calculated using the data extracted from the 2D RHI diagrams. The changing of the atmospheric conditions and the variation of the elevated aerosol layer in lower troposphere were described.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 1521147A sample of ionospheric scintillation activity measured in the African sector was analysed using GPS scintillation monitor sattioned in Douala, Cameroon. The data were provided by European Space Agency (ESA) in order to perform morphological assessment of the scintillation activity is presented together with a description of the potential threats to GNSS based applications.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 1987835The functioning of standard phase locked loops (PLL), including those used to track GNSS signals, is based on a linear approximation valid in case of small phase errors. Such an approximation represents a reasonable assumption in most of the propagation channels. However, in presence of a fading channel the phase error may become large and the PLL is expected to operate in a non-linear regime. The phase error and the performance of a PLL embedded into a commercial multi-constellation GNSS receiver was analysed in the presence of ionospheric scintillation. The limitation of the linear approximation becomes evident for a scintillation level given by S4 ≥ 0.6. The limitations posed by a fading channel consist of an increased phase dynamics together with power fading. The presence of fading on the signal power causes the absorption of the propagating energy in such a way that the PLL is forced to lose lock, irrespective of the phase dynamics.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 2118395The development of the LOw Frequency telescopes ARray (LOFAR) has posed a serious issue on the calibration of those measurements in the presence of the Earth's ionosphere. The purpose of measuring at radio frequencies as low as VHF exposes LOFAR to a number of ionospheric phenomena, capable of deteriorating the accuracy of the measurements and subsequently of the sky imaging. The ionosphere is normally treated at signal processing level, where various efforts attempt to remove possible errors introduced by it. Here, a close look at particular ionospheric features and their possible consequence to radio astronomy measurements is given from a point of view of the ionospheric radio wave propagation. It seems the radio astronomy and ionosphere communities will need to work closely together in order to achieve a satisfactory solution to the problem.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 2118651Two EISCAT measurement campaigns were set up in the framework of the Trans-National Access programme, in order to infer and calculate all those parameters useful for numerical modeling of scintillation events. The radar measurement results are compared with transionospheric radio signals at VHF, UHF, and L band in order to understand the feasibility and appropriateness of the two approaches.
B.03 Paper at an international scientific conference
COBISS.SI-ID: 2118139