# GNSS Jamming Observed on Sounding Rocket Flights from Northern Scandinavia +
## 4 Conclusions  
On most sounding rockets launched from Esrange since the end of 2022, interference caused the DLR Phoenix-HD and Novatel OEM719 receivers to lose the navigation solution at some point during the ascent and only recover it after the parachutes were deployed. On the sounding rocket launched from ASC, however, interference indeed reduced the signal quality, but not enough to stop the GNSS receivers from computing a navigation solution. Geometric considerations made it possible to roughly localize the source of the interference signals from the points of the flight path marking the start and end of interference. For that, a minimum elevation mask of the interference signal lobe was assumed. The C/N\({}_{0}\) ratios and power spectra which have been recorded on sounding rockets since the end of 2022 revealed the following:  
* Interference can be observed at Esrange at an altitude above 22 km and at ASC at an altitude above 36 km and reaches even up to the apogee of the trajectory;
* The power of the interference signal is stronger at Esrange than at ASC and decreases the average C/N\({}_{0}\) ratio by 5-10 dB;
* Interference affects the GPS L1, Galileo E1 and BeiDou B1C and B1I frequencies as well as the GLONASS FDMA frequency band;
* The interference signals are probably bandlimited white noise on various carrier frequencies with a bandwidth of about 2 MHz, 3 MHz or 7 MHz;
* Interference seems to be permanently active. The fact that the power of the interference signals exactly covers the three signals in the L1 band used by the different GNSS, the high power of the interference signals, the long duration of the interference for more than one year and the reporting of interference by airliners in large areas of northern Europe are strong indications that the interference is  
Figure 6: Scene viewed from the northeast. The green parts of the trajectories that are below the elevation mask are not affected by the jamming signal; the orange parts, however, that are above the elevation mask are affected by the jamming signal. most likely intentional jamming and not unintentional, for example, due to a misfunction of a terrestrial transmitter. It is expected that the jamming will be indefinitely active in northern Scandinavia in the future. It will therefore be necessary to adapt the current navigation system of the sounding rockets to the new conditions. On future sounding rocket missions, the jamming signal shall be analyzed in more detailed. This includes the modulation of the jamming signal and the interference of the navigation signals in the L2- and L5-bands. Furthermore, even greater efforts will be required to reduce on-board interference to improve the GNSS signal quality by default and thus increasing receiver robustness against external interference. To make GNSS more robust for future sounding rocket flights, work has begun on controlled reception pattern antennas (CRPAs) for sounding rockets that are capable of nulling the jamming signals. For example, [7] describes how a GNSS CRPA was successfully applied to detect, localize and isolate radio frequency interference. Furthermore, it is intended to use DLR's GALANT receiver which is able to additionally form reception beams to the single GNSS satellites. Alternatively, the installation of a local triangulation system is being considered, consisting of three base stations distributed on the ground on the rocket range and a transponder on board the sounding rocket. By using proprietary ranging signals with frequencies other than GNSS, the navigation system is most likely more robust against jamming. The flight guidance and range safety of future micro launch vehicles to be launched from the new spaceports in Sweden and Norway may be affected by the observed GNSS jamming if their navigation systems overly rely on the availability and quality of a GNSS navigation solution.