The Committee on Radio Astronomy Frequencies (CRAF) has been admitted as an I-member of the International Special Committee on Radio Interference (CISPR), the international body that sets standards to prevent electronic devices from interfering with each other. The effort was led by ASTRON radio astronomer Dr Emma van der Wateren, who has contributed to international discussions on unintended electromagnetic radiation from satellites and its impact on radio astronomy. The membership enables radio astronomers to contribute their expertise to international discussions on electromagnetic compatibility standards, helping ensure that both satellite services and radio astronomy can coexist.
Published by the editorial team, 24 September 2025
In recent years, the number of satellites launched into orbit has greatly increased. While these systems provide essential services, including global connectivity, navigation, and Earth observation, they also generate unintended electromagnetic radiation (UEMR) not linked to their intended communications. These radiations may arise from the satellites’ internal electronics and can leak across wide frequency ranges.
CRAF, an expert committee of the European Science Foundation (ESF), represents the interests of radio astronomy observatories and research institutes across Europe and South Africa, as well as international organisations, with the shared goal of preserving the operating conditions for radio astronomy and other basic sciences. CISPR, part of the International Electrotechnical Commission (IEC), sets global standards to limit electromagnetic interference. With its new role in CISPR, CRAF can ensure that the impact of interference on radio telescopes is considered in future standardisation.
“Radio telescopes like LOFAR are designed to detect the faintest traces of radiation from the Universe,” said van der Wateren. “But measurements increasingly reveal interference from satellites that were not meant to be transmitting in those frequencies. The challenge is cumulative: one satellite alone is not the problem, but thousands together can fundamentally change the radio environment.”
Using the LOFAR telescope, researchers have demonstrated the presence of unintended radiation from satellites in large constellations. Di Vruno et al. (2023) and Bassa et al. (2024) report detections of broadband and low-frequency leakage in LOFAR data, including signals within frequency bands that are protected for radio astronomy under international regulations. These findings confirm that UEMR has the potential to mask or distort the extremely weak signals from space that astronomers are trying to study. While standards for electromagnetic compatibility (EMC) already exist for terrestrial devices, they are not applied to satellites in orbit. “By joining CISPR, we can at least put the case on the table that satellites should meet emission limits similar to those expected of devices on Earth,” added van der Wateren.
For ASTRON, this step is particularly relevant as instruments such as LOFAR, and in the near future the SKA radio telescope, operate at low radio frequencies where UEMR is most apparent. Ensuring that these facilities can function as intended requires continued technical collaboration with both regulatory and industrial partners. Without such efforts, the increasing number of satellites could lead to cumulative interference that significantly degrades observations and limits the scientific return of these telescopes.
“The impact of radio interference reaches far beyond any single observatory,” Jessica Dempsey, Director of ASTRON, adds. “By working towards global standards, we can safeguard the conditions needed for the next generation of scientific discoveries.” With its admission into CISPR, ASTRON and CRAF are better positioned to advance efforts to protect the quiet skies on which radio astronomy depends, enabling future astronomers to push the boundaries of our knowledge.