# GNSS Jamming Observed on Sounding Rocket Flights from Northern Scandinavia +
## 2 Jamming Observed on Sounding Rocket Flights
### MAIUS-2 Mission  
The MAIUS-2 (Materiewellen Interferometrie unter Schwerelosigkeit) sounding rocket was launched from Esrange on 2 December 2023. It was a two-stage rocket vehicle and reached an apogee altitude of 233 km. In contrast to SOAR, each motor stage was separated after burnout and the spin was stopped at the beginning of the experimental phase. The attitude of the payload was controlled and kept stationary throughout the flight until atmospheric re-entry. The payload was decelerated by parachute and recovered after landing. The payload was equipped with a wraparound antenna and an additional inertial navigation system. Figure 2 shows the C/N\({}_{0}\) ratios and the number of tracked satellites. The average C/N\({}_{0}\) ratio of 39 dB-Hz at the beginning of the flight was slightly worse  
Figure 1: C/N\({}_{0}\) ratios for the GPS signals tracked by the DLR Phoenix-HD GPS receiver on SOAR. than on SOAR. The reason for this was electromagnetic interference from the payload electronics and inadequate shielding of the antenna and receiver against interference on board. At T + 33.6 s, at an altitude of about 22.5 km, the average C/N\({}_{0}\) ratio dropped below the minimum threshold of 31 dB-Hz but increased again to values between 32 dB-Hz and 35 dB-Hz at higher altitudes. On the descent, the average C/N\({}_{0}\) ratio fell again below 32 dB-Hz and rose again afterwards. Contrary to SOAR, the receiver was indeed able to track the carrier and code of most of the signals during the coast phase but the signals were not properly bit- and frame-locked so that none of the signals could be used for computing the navigation solution after T + 33.6 s. During the re-entry, the payload did not spin stably like for SOAR due to the missing fins but was in a highly dynamic flat spin motion which hindered the reacquisition of the GPS signals even without jamming effects. The coarse trajectory was provided by the inertial navigation system instead. Figure 3 shows the power spectrum of the baseband signal, which was generated by the Novatel OEM719 receiver at different altitudes. The power spectrum covers the L1 frequency band between 1531 MHz and 1631 MHz. The black line represents the power spectrum shortly after lift-off at an altitude of 2 km. The blue line represents the power spectrum at an altitude of 30 km, and the red line illustrates the power spectrum near the apogee at an altitude of 233 km. For reference, the grey line shows the power spectrum that was recently recorded on board of a test aircraft on a flight over Finnmark at an altitude of about 13 km. The spectrum at 2 km is clean and shows no peculiarities. Only at 1575.42 MHz, where the navigation signals of several GNSS are centred, does the spectral density rise above the noise floor. Centred at 1562.098 MHz and at 1575.42 MHz, additional jamming signal power with a bandwidth of about 2 MHz and 3 MHz, respectively, becomes visible at altitudes of 30 km and 233 km. Furthermore, additional signal power is received between 1598 MHz and 1605 MHz. It is noticeable that the noise floor of the power spectrum at 30 km is roughly 5 dB above the noise floor of the power spectra at 2 km and 233 km. This is due to the automatic gain control (AGC), with which the GNSS receiver optimizes the analog signal level for the range of the analog to digital stage. The power spectrum of the jamming signal at 1562.098 MHz is at 30 km about 19 dB and at 233 km about 11 dB above the undisturbed noise floor at 2 km. Due to the flat profile of the power spectrum of the jamming signal at 1562.098 MHz, the jamming signal may be bandlimited white noise modulated on the carrier. The power spectrum of the jamming signal at 1575.42 MHz is at 30 km about 18 dB and at 233 km about 12 dB above the undisturbed noise floor at 2 km.