The paper shows the results of a first test of two multi-constellation, multi-frequency GNSS receivers on board the MAPHEUS-15 sounding rocket, which was launched from Esrange, Sweden, on 11 November 2024. During the flight, the GNSS receivers tracked the signals from up to 40 satellites simultaneously and were thus able to continuously compute a navigation solution from lift-off until atmospheric reentry and during the landing phase on the parachute, even in the presence of jamming. The flight test showed that the robustness of the navigation solution could be noticeably improved by increasing the number of constellations and signals.