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 were also found to generate unintended electromagnetic radiation (UEMR), radiation not linked to their intended communications,” says Committee on Radio Astronomy Frequencies (CRAF) Chair Benjamin Winkel (MPIfR). Unlike traditional transmission signals, UEMR arises from the satellites’ internal electronics and can leak across wide frequency ranges. Studies conducted with radio telescopes around the world have confirmed the presence of such signals, including signals within frequency bands that are internationally protected for radio astronomy.

The 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 in preserving the operating conditions for radio astronomy and other basic sciences.

“Starting with an experiment at the European Low Frequency Array (LOFAR) by members of CRAF and the Square Kilometre Array Observatory (SKAO), radio observatories around the world have by now confirmed the presence of such radiation” according to Federico Di Vruno (SKAO), who led the initial observing campaign. “UEMR also occurs within frequency bands that are internationally protected for radio astronomy operations as defined in a United Nations treaty through the International Telecommunication Union (ITU-R)”, Gyula Józsa (MPIfR) adds, coordinator of CRAF's satellite group and co-author on the original paper.

"Radio astronomy is vulnerable to interference, as it relies on the detection of extremely faint signals originating from distant stars, galaxies, and the early Universe", former CRAF Chair Michael Linqvist (OSO) explains. Even weak leakage from large numbers of satellites can significantly degrade the scientific environment. Without technical and regulatory safeguards, radio telescopes risk losing their ability to conduct research.

"The International Special Committee on Radio Interference (CISPR), part of the International Electrotechnical Commission (IEC), sets global standards to limit electromagnetic interference. With its new role in CISPR, CRAF will advocate for the protection of radio astronomy and try to ensure that the impact of interference on radio telescopes is considered in future standardisation.", CRAF member Emma van der Wateren (ASTRON) adds, who represents CRAF at CISPR and led the efforts to become a member.

"CRAF’s admission to CISPR creates the opportunity for the committee to work with administrations, industry stakeholders, and technical experts on proposals for an international electromagnetic compatibility (EMC) standard for satellites in orbit", van der Wateren continues. If taken forward, such a standard would aim to ensure that satellites comply with limits on unintended radiation, much like terrestrial electronic devices must adhere to EMC rules to protect nearby equipment. "This would represent the first coordinated global step towards developing an EMC standard for satellites, with the goal of mitigating UEMR and safeguarding radio astronomy", so van der Wateren.

In addition to the efforts with CISPR, Linqvist and van der Wateren are engaging with the International Organization for Standardization (ISO) through their respective national standardisation bodies, Swedish Institute for Standards (SIS) in Sweden and Netherlands Norm (NEN) in the Netherlands. These discussions explore the possibility of initiating work on an EMC standard for satellites in operation at ISO, complementing efforts within CISPR.