Broadband polarized radio emission detected from Starlink satellites below 100 MHz with NenuFAR

¹ LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS, 92190 Meudon, France
² Observatoire Radioastronomique de Nançay (ORN), Observatoire de Paris, Université PSL, Univ Orléans, CNRS, 18330 Nançay, France
³ ASTRON, Netherlands Institute for Radio Astronomy, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
⁴ LUX, Observatoire de Paris, Université PSL, Sorbonne Université, CNRS, 75014 Paris, France
⁵ LPC2E, OSUC, Univ Orléans, CNRS, CNES, Observatoire de Paris, 45071 Orléans, France
⁶ Department of Astronomy and Carl Sagan Institute, Cornell University, Ithaca, NY, USA
⁷ IRA NASU, Institute of radio astronomy of NAS of Ukraine, Kharkiv, Ukraine
⁸ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
⁹ LOFAR ERIC, Oude Hoogeveensedijk 4, Dwingeloo, The Netherlands
¹⁰ Université Paris Cité and Université Paris Saclay, CEA, CNRS, AIM, 91190 Gif-sur-Yvette, France

^★ Corresponding author: Xiang.Zhang@obspm.fr

Received: 17 February 2025
Accepted: 11 April 2025

Abstract

Aims. We evaluate the impact of Starlink satellites on low-frequency radio astronomy below 100 MHz. We focus on challenges of the data processing and on scientific goals.

Methods. We conducted 40 hours of imaging observations using NenuFAR in the 30.8–78.3 MHz range. Observations included both the targeted tracking of specific satellites based on orbital predictions and the untargeted searches focused on high-elevation regions of the sky. Images in total intensity and polarimetry were obtained, and full Stokes dynamic spectra were generated for several hundred directions within the field of view. The detected signals were cross-matched with satellite orbital data to confirm the satellite associations. We performed detailed analyses of the observed spectra, polarization, and temporal characteristics to investigate the origin and properties of the detected emissions.

Results. We detected broadband emissions from Starlink satellites, predominantly between 54–66 MHz, with flux densities exceeding 500 Jy. These signals are highly polarized and unlikely to originate from ground-based radio frequency interference or reflected astronomical sources. Instead, they are likely intrinsic to the satellites, and distinct differences in the emission properties are observed for the different satellite generations. These findings highlight significant challenges to the data processing and scientific discoveries at these low frequencies and emphasize the need for effective mitigation strategies, in particular, through collaboration between astronomers and satellite operators.