GPS IIR-M L1 Transmit Power Redistribution: Analysis of GNSS Receiver and High-Gain Antenna Data

Abstract

All seven operational GPS Block IIR-M satellites have been subject to short maintenance periods between February 7 and 8, 2017. With the help of data from several tracking stations of the International GNSS Service (IGS) and high-gain antenna measurements, it could be identified that the satellites’ transmit power of different L1 signal components has been changed during the maintenance. The analysis shows that the total radiated power of the satellites remains constant, but the power of the C/A-code and the P(Y)-code signals are increased whereas the powers of the M-code and the intermodulation product are reduced. A detailed look reveals a more efficient use of the total available power on the spacecraft through the decreased power of the intermodulation product. Thus, in sum more power is available for the three navigation signals on L1. Observations from geodetic GNSS receivers have been analyzed to demonstrate the effect of the change in L1 signal power distribution on the measured C/N0 of the C/A-code and P(Y)-code for different receiver types. High-gain antenna data collected before and after the maintenance periods are used to analyze improved utilization of the available power through the reduction of the losses caused by the intermodulation product.