Combined Technologies Help Astronomers Fight RFI

An unlikely source of RFI that was compromising signals received by a radio telescope in Western Australia has been identified as an airplane deflecting broadcast signals. Realising that the ever-growing presence of orbiting satellites may pose the same hazard, causing astronomers' data to become contaminated, scientists have devised what they hope is a solution.

The stray signals that were interfering with the sensitive telescopes in the Murchison Widefield Array were even more puzzling because the array is an area designated by the government as a radio quiet zone. Stranger still, the signal turned out to be a broadcast signal from Australian TV and appeared to move across the sky. Researchers at Brown University in the US who are involved with the Murchison project, determined that an airplane had been deflecting the signal, and had likely been doing so for nearly five years.

This form of signal deflection, of course, held implications for other objects in the sky, most prominently, satellites whose numbers are growing each year. With this in mind, researchers at the university devised a method of filtering the RFI via a new method that combined two existing technologies already in use: Near-field corrections and beam forming. The former allows the radio telescope to adjust to closer objects more accurately instead of strictly peering into deep space. The latter adds to the sharpened focus through use of a beam, just as its name suggests. Using this combination, scientists confirmed that the RFI had been deflected off an airplane moving at 492 miles per hour and had originally been transmitted by Channel 7 on Australian digital TV.