Major threats and challenges for present and future radio astronomical observations and VLBI technique
Creators: name: Tornatore, Vincenza
Publisher: name: Zenodo
Year: 2023

description: The highly increasing global connectivity has raised significant concerns on the impact of new technologies radio astronomy observations. An unprecedented effort is nowadays needed to protect and preserve astronomical research against old and new active radio services, in particular the telecommunication systems including large satellite constellations and 5G networks . In this context, the committee on radio astronomical frequencies (CRAF) has been involved in the protection of European radio astronomy observatories and research institutes since its foundation in 1988.<br> Today, large satellite constellations consist of thousands of low Earth orbit (LEO) satellites that are being deployed by companies such as SpaceX, OneWeb, and Project Kuiper (a project led by Amazon) having the potential to revolutionize the telecommunications industry by providing global connectivity. According to current plans, more than 50,000 satellites will be launched in the next decade. Of special interest to radio astronomer are the downlink frequencies on which the satellites transmit data to the user terminals. Current plans by the industry range from less than a GHz up to 100 GHz. This downlink signal can impact sensitive observations in the radio astronomy service (RAS) band, but can also affect such as band 5 of SKA‐ Mid or VGOS receivers. For this reason, in some European countries, licenses have been granted to constellation operators with the prohibition of transmitting in spot areas centred around radio observatories. In the meantime, a new hot topic has emerged – operating normal cell‐phone base stations on satellites to connect normal smartphones to satellites.<br> Another very worrying development is currently seen in the preparation of the next World Radiocommunication Conference (WRC). Cell‐phone stakeholders would like to get a significant part of the spectrum in the so‐called mid‐band. This would heavily impact observations of the methanol spectral line at 6650‐6675.2 MHz. At the moment, it is unclear whether this band will be identified for cell‐phone use at the ITU‐R level, but many European countries are prepared to use the 6‐GHz band for either cell‐phone networks or high‐bandwidth WiFi. CRAF was heavily involved in the discussions and also contributed several compatibility calculations, which we will present. Studies showed that the huge conducted power levels of cell‐phone base stations would have high impact on any RAS operations, including VLBI and huge coordination zones (several 100 kilometers) would be required.<br> In conclusion, the deployment of large‐scale satellites and 5G networks raises concerns for the astronomical community. The situation is difficult, but CRAF continues to work to incorporate the necessary regulations for the protection of radio astronomy from large satellite constellations or cell‐phone networks. The interference caused by these active radio services can degrade the sensitivity and accuracy of scientific observations, which are critical to our understanding of the Universe. A special focus on spectrum management and monitoring activities at Italian VLBI stations will also be given while presenting some of the major challenges that need to be faced in the future.