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Ionospheric scintillation effects from GPS signals
Lookup NU author(s)
Dr Hal Strangeways
Ho YH, Strangeways HJ, Aquino M
Conference Proceedings (inc. Abstract)
International Satellite Beacon Symposium
Campus Nord of the Universitat Politècnica de Catalunya, Barcelona
Year of Conference
7-11 June 2010
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The problem of determining tracking jitter error from just time-domain data using both amplitude and phase scintillation indices, as well as an estimated value of the Fresnel frequency, (as proposed by Strangeways1) has been investigated using high latitude high frequency rate GPS data. This has been done both using (i) a Fresnel frequency estimated using the amplitude PSD (in order to check the accuracy of the method) and (ii) an assumed value of Fresnel frequency for an hour’s data period (for the real situation where contemporaneous frequency spectra are not available). An example is presented here for data (from a receiver at Longyearbyen2 (78.1690 N, 15.9920 E), for a time period of 1900 – 2000 UT on 7th May 2008). Both of the spectral parameters
T calculated using this method give quite good agreement with their determination using a straight line fit to the slope of the phase PSD in dB. There is also good agreement between the
T values calculated using the Fresnel frequency determined from the amplitude spectra and the results obtained using a constant estimated Fresnel frequency, 3Hz, as would be avoid obtaining amplitude spectral. For this data set, it is found that there can be a significance difference in the scintillation level observed on the paths from different satellites received simultaneously at the receiver location. Since Aquino et al.2 found that the positional accuracy can be improved by use of the tracking jitter variance to weight the measurements from each satellite used in the positioning calculation, this method is tried on this data set in order to quantitatively determine the increase in positional accuracy which can be achieved by using weightings which are derived from the determined tracking jitters for each satellite using the Strangeways1 method. This has significant advantages for scintillation mitigation since this process can be accomplished in this way, utilizing only time domain measurements, thus obviating the need for continual determination of phase PSDs via FFTs.
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