Radio astronomy is under threat from a silent invader: satellite radio pollution. But this time, the culprit isn't the much-discussed low Earth orbit constellations like SpaceX's Starlink. The real concern is lurking 36,000 kilometres above us, in the realm of geostationary satellites.
These satellites, positioned in a unique orbit that matches Earth's rotation, are essential for various communication purposes. But could they be secretly leaking radio emissions that interfere with our study of the cosmos? This is the mystery a team of researchers set out to solve.
Using data from the GLEAM-X survey, they meticulously analyzed the radio emissions of up to 162 satellites in the geostationary and geosynchronous orbits. The results were surprising: almost all these satellites were radio-silent in the critical frequency range for astronomy.
The team set stringent limits on the radio emissions, with most satellites emitting less than 1 milliwatt of power in the specified bandwidth. Only one satellite, Intelsat 10-02, hinted at a potential unintended emission, but even this was significantly lower than emissions from low Earth orbit satellites.
But here's where it gets intriguing: the Square Kilometre Array (SKA), a highly sensitive radio telescope under construction, will operate in this low-frequency range. What seems like harmless background noise to current telescopes could become a major disruption for SKA. These findings are a crucial step in safeguarding the future of radio astronomy.
And this is the part most people miss: even satellites designed to avoid protected frequencies can unintentionally leak emissions. As satellite technology advances and satellite numbers grow, will geostationary satellites continue to be the quiet neighbors in the radio spectrum? The answer remains uncertain, leaving us with a pressing question: how can we ensure the peaceful coexistence of satellites and radio astronomy in the future?
