Astronomers developing the Square Kilometre Array Low (SKA-Low) telescope aim to detect extremely faint radio signals from neutral hydrogen dating back to the cosmic dawn, around 13 billion years ago. However, researchers have found that unintended radio emissions from SpaceX's Starlink satellites are contaminating the very frequency bands critical to this research.
A team at Curtin University analyzed 76 million radio images over 29 days using the Engineering Development Array 2, a prototype SKA-Low station in Australia. Their study, published in Astronomy & Astrophysics, identified over 112,000 individual emissions from 1,806 Starlink satellites within the 73–235 MHz range, which overlaps with SKA-Low's observation bands.
These emissions include periodic 13-kHz tones around 137 MHz occurring every 100 seconds. Unlike planned broadband transmissions, these signals result from hardware leakage and are unpredictable, making them difficult to model or subtract from astronomical data.
The interference levels are significant: some emissions reach intensities up to one million Jansky per beam, while the hydrogen signals SKA-Low seeks are near 0.00001 Jansky. Starlink's leakage can be approximately 10,000 times stronger than the cosmic signals of interest. In some frequencies, up to 30% of images showed Starlink interference, including within two International Telecommunication Union (ITU) protected bands where such signals should not appear.
Steven Tingay of Curtin University compared the leaked emissions to the brightest natural radio sources in the sky. This contamination threatens to degrade data quality and could render entire frequency bands unusable for scientific study.
Current international regulations by the ITU protect radio astronomy bands from intentional transmissions but do not address unintended emissions like hardware leakage. As a result, these emissions exist in a regulatory gray area.
SpaceX has previously worked with the scientific community to reduce optical brightness and coordinated on higher-frequency radio bands. However, managing low-frequency hardware leakage remains a challenge. The ITU is reportedly discussing the issue, but no binding regulations have been established yet. SpaceX has been informed of the findings and is open to discussions about future hardware improvements.
While algorithmic methods to mitigate interference are being explored, they are still in early stages and may require computational resources comparable to the scientific data processing itself. Ultimately, engineering solutions to reduce hardware leakage are seen as the most effective approach.
This situation highlights a broader question about how the radio spectrum is managed and protected, especially as satellite constellations grow rapidly. The decisions made now will influence the future of radio astronomy and our ability to study the universe's earliest epochs.