World Radiocommunication Conference 2023 - Pathways towards better Radio Astronomy Protection in the Evolving Satellite Epoch

The four-week-long World Radiocommunication Conference (WRC-23) concluded on Friday, December 15. While the COP28 meeting, which took place at the same time in Dubai, garnered more media attention, WRC-23 will also have a major impact on almost every human being, as decisions were made about the future use of the radio spectrum, for example allocating new cell-phone frequencies and paving the way for new air- and spaceborne communication applications. In addition, radio astronomers managed to take the first major steps towards improved protection of their extremely sensitive telescopes from satellite constellation interference.

In recent years, the number of satellites around Earth has increased almost exponentially. While the plethora of new applications and services undoubtedly have benefit, the sheer number of satellites poses a significant threat to optical, infrared, and radio astronomy alike. In response , the worldwide astronomy community, via its International Astronomical Union (IAU), founded the IAU Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (CPS).  Led by NSF’s NOIRLab (National Optical-Infrared Astronomy Research Laboratory; optical/IR) and the Square Kilometre Array Observatory (SKAO; radio), it aims to study the impact of large satellite constellations on astronomy and to seek solutions with administrations and the industry.

The protection of radio astronomy from anthropogenic transmissions (e.g. radio, TV, cell-phone networks) is in principle already well-organised. The Radiocommunication Sector of the International Telecommunication Union – the ITU-R – is responsible for ensuring fair and coordinated access to the radio spectrum for all stakeholders, including governments, industry, and scientific users. Unfortunately, the rapid development of the satellite sector has surpassed the ITU-R regulations, which did not foresee such growth . Hence, CRAF (Committee on Radio Astronomy Frequencies) and other organisations such as SARAO (South African Radio Astronomy Observatory) & SKAO have been working diligently to address this issue and have now achieved notable success.

Every three to four years, the ITU-R organises the WRC, a conference where thousands of delegates from administrations and stakeholder organisations gather for four weeks to update the so-called Radio Regulations – an international treaty which defines the rules for the use of radio spectrum. At each WRC it is also decided, which topics – agenda items – the next WRC will cover. Before new regulation can be finalised, all aspects must be studied in detail, including the effects on all stakeholders involved. This applies to all services utilising the radio spectrum, encompassing both radio astronomy and active satellite services.

As previously reported by the CPS [LINK], African and European administrations had submitted proposals for new radio astronomy agenda items (AI) to the Conference. In a challenging, but very constructive process, administrations at the WRC agreed to create a new AI related to satellites in non-geostationary orbits and radio astronomy. This will  involve studying how two of the most significant scientific radio astronomy facilities – SKAO in South Africa and ALMA in Chile – can be protected, even in frequencies that are not globally reserved (“allocated”) to astronomy. Both sites also hold immense importance for the development of their respective countries, promising significant improvements in education, infrastructure, international collaboration, and more. Additionally, the protection of other radio observatories is also addressed, with the intention of finding streamlined processes and technical solutions applicable to existing frequency allocations of the radio astronomy service for protection from the new large satellite constellations.

The coming four years will undoubtedly entail a substantial workload for all involved parties. Nevertheless, CRAF members are more than prepared to engage in this. CRAF have already developed appropriate software for conducting compatibility calculations, extensively studied the existing regulations, and initiated cooperation with satellite operators. Embarking on a new AI represents the initial stretch of the marathon; the finish line is set for the next WRC in 2027, with the hope that it will bring adequate protections for radio astronomy.

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Photo: The NOEMA observatory - The new agenda item for WRC-27 is the first to examine the effects of satellite constellations on high-frequency radio astronomy observations. NOEMA, situated in the French Alps, is well shielded from most ground-based human-made transmissions. However, large satellite constellations are visible from anywhere on Earth. Therefore, the protection of astronomical observatories should already be considered in the planning phase of new constellations. Credit: IRAM/ J. Boissier