Robustness of GLONASS Constellation and GPS Constellation

In the equatorial region, due to the presence of intense irregularities in electron density and its variability with geophysical conditions, the occurrence of scintillation is more. The median value of CNO deviation and S4 are plotted at each 3 minutes frequency interval during each one hour duration. Analyzing the CNO and scintillation over the whole month of March 2014, it is found that during 14-15 UT maximum value up to which fluctuation in CNO for GPS is 1.35 units, which is greater than the peak values of GLONASS, 1.065 units for the same hour. Except 15-16 UT during hours 13-14, 14-15 and 17-18 UT peak value of fluctuation of CNO deviation from GPS is always greater than that of CNO deviation from GLONASS. So it can be concluded that fluctuation in CNO is more in GPS than for GLONASS as calculated from Septentrio Receiver during March, 2014 data of Calcutta Station. While on checking out scintillation, peak value of scintillation on observing all the plots (13-18 hours) is found to be 1.311, which is for GPS in the 16-17 UT, while peak value of scintillation for GLONASS is found to be 1.28 in the 15-16 UT. On observing various variables values, one can conclude that, “GLONASS constellation is more robust than GPS constellation” although fluctuations are more in the beginning and ending hours but still on the whole GLONASS has much more good signal performance.