Work

A measurement-based approach to equivalent power flux density calculation, to quantify the impact of satellite mega-constellations on low-frequency radio astronomy

Year: 2026

Type: article

Abstract: Context. Satellite mega-constellations have been shown to generate unintended electro-magnetic radiation (UEMR) that impacts low-frequency radio astronomy. The Radio Regulations of the International Telecommunications Union Radiocommunication Sector (ITU-R) contain the logical basis for addressing UEMR, but the enforcement mechanisms are absent. Aims. We aim to adapt compatibility study methods based on satellite constellation simulations, in particular the equivalent power flux-density (EPFD) framework, to real-world radio telescope measurement data. Methods. We adapt the ITU-R EPFD calculation framework to radio astronomy measurement data obtained from all-sky interferometric imaging. We explicitly address the conceptual differences between forward-model EPFD calculations and measurement-based approaches, including antenna gain treatment, temporal averaging, and detection limitations. In particular, we consider low-frequency systems, which are typically wide field-of-view and interferometric instruments. Results. For the first time, we demonstrate that because all-sky interferometric observations can be interpreted as a set of simultaneous beamformed measurements they enable a direct adaptation of the EPFD formalism to measurement data. Applying this framework to low-frequency observations, we confirm previous estimations that the resulting measurement-based EPFD distributions exceed the radio astronomy interference threshold levels defined in Recommendation ITU-R RA.769-2 in approximately 50–70% of samples, depending on polarisation and the observing subset. These exceedance fractions are well above the 2% single-system data-loss criterion in Recommendation ITU-R RA.1513-2. Expressed using the conventional 2% compatibility margin, the corresponding margins are negative, ranging from -18.6 to -16.3 dB, equivalent to a required uniform attenuation of 16.3–18.6 dB. Conclusions. We show that measurement-based implementations provide a practical pathway towards verification and long-term monitoring at low radio frequencies, which could form an important component of enforceability. We suggest instrumentation approaches to support measurement.

Source: Astronomy and Astrophysics

DOI: 10.1051/0004-6361/202662188