Astronomers developing the Square Kilometre Array Low (SKA-Low) telescope, designed to detect faint hydrogen signals from the early universe, are encountering unexpected interference from SpaceX's Starlink satellites. Researchers at Curtin University analyzed nearly 76 million radio images over 29 days using a prototype SKA-Low station in Australia. They identified over 112,000 individual radio emissions from 1,806 Starlink satellites within the 73–235 MHz frequency range, which is crucial for SKA-Low observations.
These emissions are not the intentional broadband signals Starlink transmits but rather unintended hardware leakage radiating across protected frequency bands. Some satellites emit periodic tones around 137 MHz every 100 seconds, signals that are unpredictable and cannot be easily filtered out by astronomers. The detected leakage is reported to be up to 10,000 times stronger than the faint cosmic signals SKA-Low aims to observe, contaminating up to 30% of images at certain frequencies.
The interference extends into two International Telecommunication Union (ITU)-protected bands where emissions are not permitted, posing a significant challenge for radio astronomy. According to Steven Tingay of Curtin University, the leaked signals are comparable in strength to the brightest natural radio sources in the sky.
Current international regulations focus on intentional transmissions and do not adequately address unintended satellite emissions, leaving a regulatory gap. While SpaceX has previously worked with astronomers to reduce optical brightness and coordinate on higher-frequency radio bands, these measures do not mitigate low-frequency hardware leakage.
Discussions are ongoing within the ITU, and SpaceX has expressed willingness to engage on potential hardware modifications. Meanwhile, researchers are exploring algorithmic approaches to mitigate interference, though these methods are still in early stages and may require substantial computational resources.
The situation highlights a broader question about how to balance the expansion of satellite constellations with the preservation of the radio sky for scientific research. Engineering solutions similar to those used for optical interference may be necessary to protect critical radio astronomy frequencies before further degradation occurs.