An unexpected television signal traced to an airplane led to a new method for pinpointing unwanted radio signals, as growing satellite activity threatens the future of radio astronomy.
PROVIDENCE, R.I. [Brown University] - Astronomers sifting through data from the Murchison Widefield Array, a radio telescope in Western Australia, found themselves confronting an unexpected mystery.
The telescope, which consists of 4,096 spider-like antennas designed to detect radio wave signals from more than 13 billion years ago, appeared to have stumbled upon something far more local: a television broadcast. This was puzzling, given that the telescope is located in a designated radio quiet zone, where the Australian government regulates signal levels from all radiocommunication equipment - including TV transmitters, Bluetooth devices, mobile phones and more - to minimize interference with the telescopes in the area. Even more perplexing, the television signal was streaking across the sky.
"It then hit us," said Jonathan Pober, a physicist at Brown University and the U.S. research lead for the Murchison Widefield Array project. "We said, 'I bet the signal is reflecting off an airplane.' We'd been seeing these signals for close to five years, and several people had suggested they were airplanes reflecting television broadcasts. We realized we might actually be able to confirm this theory for once."
To do this, Pober enlisted Brown Ph.D. student Jade Ducharme for some astronomical detective work. The findings from the pair, published in Publications of the Astronomical Society of Australia, not only supported the airplane hypothesis but have now also provided astronomers with a new method to identify and filter out unwanted radio frequencies - a goal becoming increasingly important as Earth's skies grow noisier with the deployment of more satellites.
"Astronomy is facing an existential crisis," Pober said. "There is growing concern - and even some reports - that astronomers may soon be unable to carry out high-quality radio observations, as we know it, due to interference from satellite constellations. This is particularly challenging for telescopes like the Murchison Widefield Array, which observes the entire sky simultaneously. There's no way to point our telescopes away from satellites."
