Radio spectrum
The SKA telescope sites are located in extremely remote locations with an almost pristine radio frequency environment. Protection from terrestrial sources of interference that could disturb the astronomical observations is provided by the site location together with strict laws to regulate the use and installation of transmitting equipment in proximity to radio telescopes. These special sites are known as radio quiet zones.
However, satellites and aircraft will still pass over the sites, potentially producing interference in the frequency bands the SKA telescopes will observe at. Working closely with other astronomy organisations as well as industry and international regulatory bodies, SKAO’s spectrum management activities coordinate with industry and negotiate special agreements to ensure satisfactory solutions to mitigate the impact of satellite constellations and keep the night sky a sustainable resource for all.
In early 2022, following calls from the International Astronomical Union to address the threats to astronomy presented by low-earth orbit satellite constellations, the SKAO and the US National Science Foundation’s NOIRLab led the creation of the Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (CPS).
Over the years, including through our involvement in the CPS, the SKAO has become a leading voice on the topic of the protection of radio astronomy and the wider issue of space sustainability, engaging with all relevant stakeholders from industry, the wider astronomy community, policy-makers and governments, among others, to raise awareness of this issue with all relevant parties and at all levels. This dialogue has proven fruitful and some mitigation measures have already been adopted by satellite operators.
On the legislation front, the SKAO is actively involved in inter-governmental discussions on these issues through key United Nations bodies. Since September 2021, the SKAO has been a permanent observer on the UN Committee on the Peaceful Uses of Outer Space (COPUOS), the only UN committee dedicated exclusively to space matters. The Observatory is also a Sector Member of the International Telecommunication Union (ITU), the UN’s specialised agency responsible for allocating use of the radio spectrum.
This diplomatic engagement has already yielded several significant achievements. At the World Radiocommunication Conference 2023 held in November-December, based on thorough work during the 2019-2023 study cycle, radio astronomers from all around the world successfully advocated for further radio astronomy protection. For the first time in several four-year study cycles, it was decided to dedicate two agenda items to radio astronomy protection. One of these agenda items is directly connected to the SKAO since the SKA-Mid telescope site was identified as a facility of utmost importance. This agenda item includes the possibility of international recognition of two Radio Quiet Zones, including the SKA-Mid site, to ensure not only protection of designated radio astronomy bands but also a possibility to improve scientific access to other parts of the radio spectrum which can be significantly impacted by satellite transmissions.
At the February 2024 meeting of the UN COPUOS Scientific and Technical Subcommittee, thanks to several years of thorough work by astronomers and astronomy organisations such as the SKAO to quantify and communicate the impact of satellite constellations on existing and upcoming astronomy facilities, the subcommittee agreed to include an item on the COPUOS agenda for the next five years titled “Dark and Quiet Skies, astronomy and large constellations: addressing emerging issues and challenges”.
