A communication satellite that has been decommissioned for nearly 60 years suddenly emitted a strong radio signal detected by astronomers, leaving experts puzzled.
According to a report by CNN, in June last year, Clancy James, associate professor at Curtin Institute of Radio Astronomy at Curtin University in Australia and his colleagues detected a strange radio signal using the Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope array.
Normally, the team would use ASKAP to search for fast radio bursts, which are energy flashes emanating from distant galaxies.
James stated that the signal they detected was very short, lasting only about 30 nanoseconds, but extremely powerful, and they were unsure of its origin. Some astronomers speculate it could come from a magnetar, a type of dead star’s dense remnant with a powerful magnetic field.
However, this signal appeared to come from a location very close to Earth, so close that it couldn’t possibly be of celestial origin. James and his colleagues discovered that the signal was only about 4,500 kilometers away from Earth, matching the location of the decommissioned communication satellite “Relay 2” from the National Aeronautics and Space Administration (NASA).
“Relay 2” was launched in 1964 as an upgraded version of “Relay 1” launched two years prior, used to relay signals between the United States and Europe, and it even broadcasted the 1964 Tokyo Summer Olympics.
Just three years later in 1967, “Relay 2” was retired after both of its main instruments malfunctioned. It was eventually decommissioned, becoming space debris. It has since been orbiting aimlessly around Earth until James and his team detected its peculiar signal.
So, why would this decommissioned satellite still be emitting signals? James explained that there are two possible reasons. The most likely reason is that the satellite’s metal casing discharged static electricity it had accumulated, resulting in a short circuit. “Relay 2” being an early satellite, its materials are more prone to static buildup compared to modern satellites.
Another possibility is that the satellite was struck by a high-speed micrometeorite, creating high-temperature plasma at the impact point, thereby releasing brief radio waves. However, this scenario requires very specific conditions, making it less probable.
James said they were attempting to detect fast radio bursts from space, but if satellites could also produce such bursts, they would need to proceed with caution. This implies that astronomers must be more vigilant about potential interference from artificial satellites during space observations.
He stated, “As more and more satellites are launched, such experiments will become increasingly challenging.”
The research findings were published on June 13 in The Astrophysical Journal Letters.