# GNSS Jamming Observed on Sounding Rocket Flights from Northern Scandinavia +
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Mission** & **Lift-Off Time (UTC)** & **Launch Site** & **Jamming** & **PVT Interrupted?** \\ \hline PMWE-2 FIONA & 1 October 2021, 10:03:00 & ASC & no & no \\ PMWE-2 DUSTIN & 1 October 2021, 10:06:00 & ASC & no & no \\ MAPHEUS-10 & 6 December 2021, 08:07:00 & Esrange & no & no \\ MAPHEUS-9 & 29 January 2022, 07:00:00 & Esrange & no & no \\ STORT & 28 June 2022, 02:19:00 & ASC & no & no \\ TEXUS-57 & 1 October 2022, 06:26:00 & Esrange & weak & occasionally \\ MAPHEUS-12 & 21 October 2022, 07:25:00 & Esrange & no & yes, due to technical issue \\ REXUS-27 & 5 November 2022, 09:07:00 & Esrange & yes & yes \\ REXUS-28 & 7 November 2022, 06:43:00 & Esrange & yes & yes \\ REXUS-30 & 29 March 2023, 04:30:00 & Esrange & yes & yes \\ REXUS-29 & 1 April 2023, 04:20:00 & Esrange & yes & occasionally \\ TEXUS-58 & 24 April 2023, 05:20:00 & Esrange & yes & occasionally \\ MAPHEUS-13 & 22 May 2023, 05:00:00 & Esrange & unknown & yes, due to technical issue \\ HIFLIER-1 & 10 October 2023, 08:00:00 & Esrange & yes & yes \\ SOAR & 13 November 2023, 12:20:00 & ASC & yes & no \\ MAIUS-2 & 2 December 2023, 07:30:00 & Esrange & yes & yes \\ TEXUS-59 & 15 February 2024, 14:42:00 & Esrange & yes & yes \\ \hline \hline \end{tabular}
\end{table} 
Table 1: MORABA’s sounding rocket missions since 2021 launched from ASC and Esrange. GNSS signal interference becomes noticeable in the carrier-to-noise (C/N\({}_{0}\)) ratio of the received signals, which is an indicator of signal quality. Normally, C/N\({}_{0}\) values are in the range between 25 and 55 dB-Hz. Signals with high C/N\({}_{0}\) values can be stably tracked by the receiver. When the C/N\({}_{0}\) value is low, noise becomes dominant and the signal tracking is hampered and may even be disrupted. If fewer than four satellites are being tracked, the GNSS receiver can no longer compute a navigation solution. Depending on the interference signal, additional noise is added to the tracked GNSS signals so that the C/N\({}_{0}\) values decrease in the event of interference. If the power of the interference signal is high enough, the C/N\({}_{0}\) values drop below a threshold value down to which the receiver is able to robustly track GNSS signals. It took quite a while to understand that the interference was not generated unintentionally on board the sounding rocket but originated externally. It was also not clear for a long time whether the observed phenomena were due to unintentional interference caused, for example, by a malfunction of a terrestrial transmitter that resulted in signal power leakage into the L1 band used by GNSS or due to intentional jamming of the GNSS signal frequencies. Over the course of 2023, however, because of its duration over several years, its high power and its coverage over a wide area, evidence was increasing that the interference was most likely intentional. This assumption was substantiated in the second half of 2023, when many airliners reported disturbances of their on-board GNSS receivers over the Baltic states and southern Finland. In December 2023, GNSS jamming was reported over the Baltic Sea and Poland. Since then, jamming has been temporarily activated in the Baltic Sea region. In 2024, this jamming was almost permanently activated. In [2], a systematic analysis of the estimated position uncertainties (NAC\({}_{\text{P}}\)) contained in the ADS-B messages sent by each aircraft in controlled airspace shows the extent and frequency of occurrence of jamming events in the Baltic region. Since 2018, Norway has been complaining about the occurrence of temporary, daily jamming in northern Norway [3,4]. Similar to the jamming over the Baltic Sea, the Baltic states and southern Finland, the number and duration of jamming events in northern Scandinavia have steadily increased since 2021. Airliners reported 18 days of jamming in the northern Scandinavian airspace in 2021, 122 days in 2022 and 294 days in 2023 [5].