Radio astronomy at the regulatory crossroads: WRC-27 and beyond

By Balthasar Indermuehle, Principal Scientist and Spectrum Manager, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Australia; Chair, ITU-R Working Party 7D

Today, the conditions under which radio astronomy is practised have changed more profoundly than at any time since the discipline began. Active services are expanding into nearly every accessible band of the radio-frequency spectrum.

Consequently, when the next World Radiocommunication Conference, WRC-27, convenes in Shanghai, China, from 18 October to 12 November 2027, it will reflect a moment when established frameworks are challenged by new realities.

This is because satellite operators are deploying constellations whose aggregate emissions can no longer be characterized by single-system assumptions.

Key instruments derived from single-system assumptions include the detrimental interference thresholds of Recommendation ITU-R RA.769, the per-system equivalent power flux density (epfd) thresholds and consultation procedure of Resolution 739 (Rev.WRC-19), and the footnotes to the Table of Frequency Allocations in Article 5 of the Radio Regulations that invoke them. WRC-27 agenda item 1.16 is the first to address aggregate interference from multiple non-geostationary orbit (non-GSO) systems explicitly.

Increasingly, these vital frameworks for spectrum and orbital coordination, developed over more than half a century, are being asked to do work for which they were not designed.

This article and related radio astronomy posts take stock of where we stand, what is at stake at WRC-27, and what the radio astronomy community must contribute to the preparatory process if the science we practise is to remain viable in the decades ahead.

Together, these articles examine radio astronomy, the facilities and instruments that support it, the changing spectrum and space environment in which it operates, and the policy and regulatory challenges increasingly emerging.