GPS Jamming: A Historical Record from Global Radio Occultation (RO) Observations

GPS jamming can be detected from the radio occultation (RO) technique during the open-loop (OL) tracking at a deeply occulted height where little signal comes from GPS transmitters behind the Earth shadow. Observations from COSMIC-1 and other GPS-RO receivers reveal several regional hotspots over USA, the Middle Asia, and the Southeast Asia during 2006- 2023. These hotspots of GPS jamming power evolved with time, showing correlation with regional conflicts and state-sponsored jamming. Jamming on L1 and L2 signals is both evident in the GPS-RO data, but their geographical distributions and evolution with time are different from each other. The L1 jamming exhibits a strong power over the North Africa and the Middle East began to increase significantly since 2018. It was spread to a wider area, including the eastern Europe in 2022- 2023 when the Russo-Ukrainian war started. On the other hand, the L2 jamming shows three predominant regions (i.e., USA, Europe and the Middle East, the Southeast Asia). While the L2 jamming power in other regions remains relatively unchanged, the jamming over the Southeast Asia experienced a substantial increase in power during 2014-2018. In 2023, the L2 jamming power over Europe, the Middle East and the Southeast Asia remain elevated. In this study we will describe in detail the technique used to extract the L1 and L2 jamming power from GPS-RO measurements, as well as a technique to monitor the GPS transmitter power from the POD antennas on these RO observation satellites.