The measured effects of GPS flex power capability collected on sensor station data

In a scenario in which several GNSS systems, GPS, Galileo, GLONASS, COMPASS, QZSS, are planning to coexist in the same frequency band, spectra/signal structure management and relative power levels are the main instruments to counteract the possible impact of intersystem interference, and the ability to increase the transmit power on individual signal components from GNSSs system providers has become an important feature of the modernized satellite payloads. Among the modernizations that GPS Block IIR-M and IIF Space Vehicles payload underwent, one of them is the capability of programmable power output also known as ¨flex power¨ capability. The flex power capability enables operators of the system to increase the signal strength of the military P(Y) and M-code signals, if needed by Department of Defense (DoD) and allied GPS users. The 2nd Space Operations Squadron (2SOPS) experimented, over the course of five days during the month of September, the use of this programmable power output capability in several SVs. This paper provides an analysis of the C/No measured from sensor stations where the transmit power level changes that GPS satellites underwent during the days from the 7th of September 2010 to the 12th can be assessed. Moreover, a theoretical analysis based on real measurements collected with the STFC (UK) 25m Radio Observatory [1] is presented, providing a possible explanation on how the flex power capability may have been implemented on board.