A Dual Frequency GPS Receiver Measuring Ionospheric Effects Without Code Demodulation and Its Application to Time Comparisons
BUREAU INTERNATIONAL DES POIDS ET MESURES SEVRES (FRANCE)
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The GPS Global Positioning System satellites have become widely used for daily time comparisons between the major time and frequency laboratories. The precision of time comparison by GPS satellites is now between one and a few tens of nanoseconds depending upon the distance between the laboratories. In the case of long-distance time comparisons, the ionospheric effect is one of the largest sources of uncertainty. To compensate for the ionospheric effect, we have developed a novel GPS receiver which measures the total electron content TEC along the signal path to the GPS satellite. It uses the property of cross-correlation between the P-code Precise-code signals which are transmitted Erom GPS satellites by L1 1575.42 MHz and 4, 1227.6 MHz, without demodulating P-code signal. Preliminary results using the prototype receiver give, for about 3 minutes observation time, an uncertainty in the measurement of TEC of 2 x 1016m2, equivalent to an uncertainty in the delay of L1 signal of 1 ns. We have begun to apply the results of this receiver to the time comparisons between USA and Europe.
- Navigation and Guidance