After adapting the data-acquisition electronics accordingly, a prototype station including three radio antennas was installed at the South Pole in January 2020, and data has regularly been transferred by satellite. The subsequent data analysis showed that indeed we successfully measure cosmic-ray air showers with the prototype station.
However, in March 2020 the Covid pandemic and world-wide travel restrictions disrupted these plans. In particular, access to the South Pole station has been limited such that only existing instrumentation can be maintained, but no new deployments were possible for three years. As travel to the best among the backup sites for this project, the Pierre Auger Observatory in Argentina, became possible, we have completed the installation of a prototype station there end of 2022. In parallel, we prepared the hardware for further installations at both the South Pole and the Pierre Auger Observatory: several stations are completely ready to ship and several antennas have been shipped to both sites in 2024 and subsequently deployed with the help of the Pierre Auger Observatory and of IceCube collaborators at the South Pole.
Although the deployment of new instrumentation was not allowed at the South Pole through the 2022/23 season, one PhD student of the project was permitted to upgrade the existing prototype station. After successfully defending her PhD in November 2022, she was at the South Pole changing the antenna mount to the final design that she developed as one part of her PhD work on the project.
Being limited in the deployment of instrumentation, we also used the time to accelerate other aspects of the project, in particular, the preparation of software, simulations studies, the analysis of the data of the prototype station, and preparations for further data analysis. These preparations with simulation studies cover in particular important points: a) the reconstruction of the energy and position of the shower maximum of the cosmic-ray air showers, as the latter is one of the most accurate estimators for the mass of the primary particles, and b) the separation of photons against other cosmic particles using all of IceCube’s instrumentation. The latter is the work of the second out of two PhD students working on this project. He has significantly enhanced the gamma-hadron separation of IceCube to a level that provides a realistic discovery potential of PeV photon sources.
Results have been disseminated regularly at international conferences and published in the corresponding proceeding papers.
Although the Covid related delays prevented physics discoveries within the project duration, the project will still have several long-term impacts:
- the methods developed in this project will facilitate future discoveries of cosmic-ray sources
- the successful operation and data analysis of the prototype station led to the decision to include such radio antennas in the reference design of the proposed next-generation observatory IceCube-Gen2
- existing data remain available for future analyses and the antennas deployed remain operational for future data taking
Therefore, the project has been a manifold success, despite the pandemic preventing the timely achievement of the originally set goals.
