Each September, Norwegian authorities run a week of jamming and spoofing attacks over the Arctic island of Andøya from the village of Bleik, 69 degrees north. The event, Jammertest, lets institutions and industry test positioning, navigation and timing technologies against realistic interference, according to ESA, which has taken part since 2023. The agency describes jamming as a powerful signal that drowns out satellite signals, spoofing as false signals that produce an incorrect location, and meaconing as the capture and rebroadcast of real satellite signals.

For two hours on the afternoon of Wednesday 16 September, five operational Galileo satellites over Europe transmitted a new encrypted signal. ESA says ground receivers at the site successfully established their location using it, the first real-world positioning with Galileo's upcoming Signal Authentication Service. The service, together with Open Service Navigation Message Authentication, is intended to help receivers detect and reject spoofing attacks.

ESA also reported that both Celeste demonstration satellites flew over Andøya, with preliminary results indicating their signals were acquired by ground receivers, including under contested conditions. The data will be analysed further at ESA's navigation laboratory. The agency said its teams now have dozens of terabytes of data to post-process, with lessons feeding into its navigation programmes throughout the year.