Workshop 2018
Yoaz Bar-Sever - What to do about Flex Power - October 29, 2018 • 464 Views
Since January 2017 GPS satellites have been operating in a new regime called Flex Power Mode (FPM). Under FPM the power output of some of the GPS signals change, sometime radically and frequently. Some FPM events are cycled regularly, and some irregularly, such as the extreme FPM (EFPM) event of April 13-17, 2018, which resulted in global disruption to GPS reception and to various orbit determination and positioning applications. We will describe the various FPM regimes, their monitoring, and their impact on GPS receivers and on precision GPS applications, including the orbit determination operations at IGS Analysis Centers. We will show that FPM induces significant rapid changes to certain differential code biases (DCB), which invalidate daily and monthly estimates of DCBs. Alternative monitoring and estimation techniques will be described, such as the 5 minute, real-time estimation of DCB carried out at JPL. Finally we will discuss various approaches to mitigate the effects of FPM on precision GPS applications and provide our recommendation to the IGS community for coping with the reality of a persistent but variable FPM regime.

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