When Satellites Confuse SETI


By Morris Jones

SETI astronomers sometimes pick up strange signals. They don’t look like the regular type of radio transmissions we get from stars and other natural things in space. When this happens, they pay attention. These signals could be transmissions from extraterrestrials. 

There are protocols for dealing with a potential extraterrestrial discovery. You perform follow-up observations of the same source, or the same area of space. You ask other observatories to perform their own observations. You also avoid saying too much in public until you know the real source of the signal.

SETI observations have gone down this path many times, and in all cases, no evidence of extraterrestrial intelligence was found. Sometimes, signals have come from aircraft. But an increasing source of strange signals comes from our own fleet of satellites.

Recently, the red dwarf star Ross 128 was the subject of one such incident. Astronomers from the famous Arecibo radio telescope picked up weird transmissions from the directions of this star, even though they were not actively conducting a SETI search. They alerted other astronomers and even published news of these investigations on a Web page. The media got hold of the story and published it. Much hype was made about the potential discovery, despite the fact that the astronomers had downplayed the likelihood of extraterrestrial involvement. But that doesn’t sound so juicy to journalists hunting for a big story.

It was quickly shown that extraterrestrials were not beaming messages into space from Ross 128. But something else was certainly transmitting. The most likely cause, it seems, was a satellite orbiting the Earth. It just happened to be passing over the telescope’s field of view when these observations were taken.

There’s a tremendous amount of artificial radio transmissions on Earth and in space. That’s how we sustain our information society. But the widespread use of radio waves causes problems for radio astronomers, SETI or otherwise. In the future, astronomers may need to go deeper into space, perhaps to the far side of the Moon, to escape the radio noise of Earth.

That’s a luxury SETI astronomers can’t afford right now. All they can do is check any strange signals carefully, and accept that there will probably be more interference from satellites in the future.

This also means that discipline needs to be practiced in reaching wild conclusions too quickly. Look before you leap. Check before you talk. In 2016, there was a torrent of publicity over a strange signal received by the RATAN-600 radio telescope, which was suspected of being an extraterrestrial transmission. Follow-up observations dispelled any chance of this, and it seems that once again, astronomers were tricked by a satellite. In this case, there was clearly too much talk before the signal had been properly investigated.

These two incidents serve as lessons for SETI practitioners, the media and the public. Any strange signal detected by a SETI project is probably not from extraterrestrials. The most likely cause will probably be a satellite launched by humans from Earth. We all need to avoid leaping to wild conclusions without firm evidence. Getting that evidence takes time, and patience will be needed.

We would all love to find evidence that humanity is not alone in the universe. It’s one of the most significant questions confronting science. But science shouldn’t run on emotions. It needs caution and deduction. SETI is mostly a well-run pursuit. But journalists and the public should still be cautious of any claims they encounter.