Radio astronomy in times of Starlink & Co.: technology to reduce interference
The number of satellites is increasing rapidly, which is becoming a problem for astronomy. An unexpected TV signal in Australian measurement data could now help.
Antennas of the Murchison Widefield Array in Australia
(Image: ICRAR/Curtin)
A research team from the USA may have taken an important step towards protecting radio astronomy from increasing contamination by satellite networks. As Brown University in the US state of Rhode Island explains, Jonathan Pober and Jade Ducharme have found a way to identify and filter out unwanted signals in the measurement data from a radio telescope in Australia. This is so important because it involves television signals that were reflected by an airplane flying over the Murchison Widefield Array. Normally, the contaminated data would have to be discarded. However, they could soon be saved.
Even the television transmitter recognized in the measurement data
The Murchison Widefield Array has a diameter of several kilometers and observes the entire sky in the radio spectrum from a special protection zone in Western Australia. For this reason, it may not be able to avoid interfering signal sources such as satellites, write the researchers. When they recognized television signals in the collected data, which also appeared to move across the sky, they were initially perplexed. But then they realized that they must be reflections from an aircraft. Together, they then took the opportunity to try out methods that could be used to filter out the signals.
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By combining two tried and tested methods, the team was not only able to trace the exact path of the aircraft in the measurement data, but even determine its position and speed. They even discovered that the reflected television signals must have originated from the Australian digital television channel Channel 7, they write. They were only unable to identify the exact flight due to incomplete tracking data. This has given radio astronomy a key to removing human-induced interference from the data without having to discard the data itself, they write. The next step is to refine the method.
The research work has taken place against a backdrop of growing concerns about radio astronomy; Jonathan Pober even speaks of an "existential crisis". He is referring to the interference caused by the rapidly increasing number of satellites orbiting the Earth, primarily due to the construction of Starlink. These also interfere with astronomical observations in places where special protection zones for astronomy have been set up on the ground, in which radiation is avoided as far as possible. However, the work on identifying the reflected television signals now presented in the journal Publications of the Astronomical Society of Australia suggests that it may be possible to remove disturbing interference from the measurement data in future.
(mho)
