“Astronomy is Facing an Existential crisis,” Says Researcher Who Solved Radio Telescope Mystery – The Debrief
An American astronomy team at Brown University was engrossed in a strange mystery when the Australian Murchison Widefield Array radio telescope recently recorded something perplexing and unexpected.More than four thousand spider-like antennas make up Murchison, designed to collect radio waves over 13 billion years old that eventually make their way to Earth after traveling from some of the most distant regions of the universe.However, the mystery began when an unexpected signal overtook this carefully tuned instrument: one originating from a local television broadcast.Murchison is surrounded by a government-designated quiet zone, where all radio communication equipment, including TV transmitters, Bluetooth devices, mobile phones, and more, are heavily regulated to avoid interfering with the area’s sensitive telescopes. Despite these precautions, a stray signal was able to mingle with the telescope’s cosmic radio readings.“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.”Like a pair of astronomical detectives, Pober, along with Brown Ph. D student Jade Ducharme, began their quest to test the hypothesis. They started with data from when Murchison first came online in 2013, since its 0.5-second recording interval at the time provided much crisper data than the two-second interval that the radio telescope switched to in subsequent years to conserve storage.Not only did they find evidence supporting the airplane hypothesis, but they also discovered a new method of identify unwanted radio frequencies. With an ever-thickening shell of satellites growing around the Earth, isolating the noise is becoming increasingly necessary.“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,” Pober said, “which observes the entire sky simultaneously. There’s no way to point our telescopes away from satellites.”Radio-frequency interference (RFI) is when a wild card signal contaminates radio telescope data, usually rendering the infected data useless. With no solid model for where the unpredictable signals originate, it has been almost impossible for scientists to isolate and remove them from a data set until now. Pober and Ducharme’s method combines near-field tracking corrections to adjust the telescope’s focus on objects close to the Earth and beamforming, a technique to generate a beam for pinpointing the source of the interference.“It ends up being insane amounts of data being thrown out to not have any part of the observation contaminated,” Ducharme said.The pair successfully tracked an aircraft with their two-stage approach and discerned how radio waves bounced off it. From the data they collected, they accurately determined that in one of about a half dozen events the pair analyzed, a plane was flying 492 miles per hour at a height of 38,400 feet. In addition to recognizing the object as a plane, Pober and Ducharme determined that the television signal was on a frequency associated with Australian Digital TV Channel 7.
See Also
Scientists Unravel Origins of Mysterious White Patch Appearing Near the Northern Lights
Unfortunately, incomplete flight logs left the team unable to determine the exact flight number. Still, their successful repurposing of existing techniques offers new avenues to navigate a challenging radio telescope environment.“This is a key step toward making it possible to subtract human-made interference from the data,” Pober said. “By accurately identifying and removing only the sources of interference, astronomers can preserve more of their observations, reduce frustrating data loss, and increase the chances of making important discoveries.”With the sourcing and identification method solved, the next step is removing the RFI from the affected data. Once that process proves successful, astronomers can move on to mitigating signals from satellites and other space objects, which are expected to be more challenging to resolve than planes. With an incredible 40% increase in Earth orbital satellites between January 2022 and June 2023, satellite interference is a timely issue. Even Pober wonders if such a feat as removing all the satellite noise will be possible in the future; perhaps building radio telescopes on the moon or beyond may be the only long-term solution.“If we can’t find a quiet sky on Earth, maybe Earth isn’t the place to be,” Pober said. “No matter what we do, we have no choice but to invest in better data analysis techniques to identify and remove human-generated interference.”Pober and Ducharme’s paper, “Altitude Estimation of Radio Frequency Interference Sources Via Interferometric Near-Field Corrections” appeared on February 12, 2025 in Publications of the Astronomical Society of Australia. Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.
