Impact of GPS Flex Power on Differential Code Bias Estimation for Block IIR-M and IIF Satellites

Kurzfassung

The modernized GPS satellites, Block IIR-M, and follow-on GPS satellites, Block IIF, can redistribute the transmit power between the signal components. This is called flex power and it has been developed as a remedy against jamming. From January 2017 until February 13, 2020, a flex power was active which was centered at 41°E and 37°N for only Block IIF satellites. On February 14, 2020, a new flex power mode is activated on both GPS Block IIR-M and Block IIF satellites centered at 37ºE/35ºN and 69ºE/35ºN. The changes in the transmit power affect the carrier-to-noise density ratio (C/N0) observations as well as the differential code bias (DCB) estimations. To see the impact of the flex power on DCB estimations, first DCBs are calculated without considering these changes. Next, a second DCB estimation is done by considering the flex power into the calculations. This time, two different DCBs are estimated for the satellite when it is inside and outside of the flex power activation area. The extension of this area is identified by analyzing flex power induced discontinuities in carrier-to-noise density ratio observations. In order to reduce the effects of the different front-end and correlator settings on estimated DCBs, a global network of exclusively Septentrio PolaRx5 and PolaRx5TR receivers is used and the results are compared with each other. Additionally, a global network of Javad receivers is used and compared with Septentrio PolaRx5 and PolaRx5TR to study the impact of using different the receivers on DCB estimations.