1 JSTARS-2023-01679 GNSS Signal Jamming as Observed from Radio Occultation

The jamming is found to increase significantly in recent years and its impact is evident in GNSS radio occultation (RO) measurements such as those from COSMIC-2. This study presents an algorithm that applies the RO radiometry to detect and monitor long-term variations of GNSS jamming power from a deeply occulted height (HSL = -140 km). At these heights the RO signal amplitude is at its noise level because the GNSS transmitter is far behind the Earth shadow. Thus, any enhanced RO amplitudes from these heights are considered as a jamming signal. The algorithm was successfully applied to two conflict zones: Mediterranean Sea and Middle East (MSME) and Central Africa (CA), where the GPS jamming was frequently used by statesponsored electronic warfare. The time series of normalized RO amplitude in these regions show a steady increase of the GPS jamming power since 2017, but a sharp decrease since the start of Russo-Ukrainian War.