Increasing radio noise makes star research more difficult

The technology developed by humans produces more and more disturbing radio signals. This makes scientific research difficult, including the use of radio telescopes for star research. During the RF Technology event Michiel Brentjens from Astron speaks about this problem.

By: Dimitri Reijerman

Brentjens conducts fundamental research on behalf of Astron into the early universe, approximately 300 million years after the Big Bang when the first galaxy and stars formed. He says: “We are talking about the first population of stars that use ultraviolet light to slightly heat up the gas in the environment. That gas started to emit radio waves with a wavelength of 21 centimeters. We try to capture those signals with the LOFAR radio telescope.”

The LOFAR radio telescope covers a large part of the European continent and goes from Ireland to Latvia and from Sweden to Germany. “And in three years we will also have an antenna station in Italy,” says Brentjens. “All together that is about seventy antenna fields. These stations are connected to a central location with a 10 gigabit link.”

But research into the early galaxy is not getting any easier, the astronomer says: “Over the past ten to fifteen years, depending on where you are in the Netherlands, the amount of background noise has become more intense by a factor of ten to a thousand. This can almost entirely be attributed to power converters and LED lighting. These are components that are crucial for the transition to sustainable energy. But we must be aware of the difference between a few LED lamps in a street and several thousand LED lamps.”

He continues: “It's about the electrical equipment we develop. And we are mainly talking about equipment that is not intended to emit radio waves, but does so anyway. Especially voltage converters: almost everything has a battery these days. These batteries all run on 3.6V or a multiple thereof. And electronics often work on 5V and must always receive direct voltage, so conversion is required. These power converters cause relatively much radio interference. And LED lighting can also cause significant radio interference for us as astronomers. We can detect LED lamps up to a kilometer away.”

Brentjens works from an office building in Dwingelo. Yet mistakes are sometimes made by astronomers, as he says anecdotally: “There is no LED lighting on our antenna facilities themselves. But still, the Irish had built a new antenna station with a visitor center next to it. There was environmentally conscious LED lighting everywhere. When the lights in the visitor center were first turned on, they could see it perfectly with their antenna field. So they have all been replaced.”

To reduce the problems with radio-interfering signals, a broad approach is needed, according to the astronomer: “Two steps are needed: a package of measures and enforcement. Both have yet to happen. If all electronics meet the applicable specifications, and the combined installations continue to meet them, we can make good progress. But an internal TNO study, for example, showed that LED lamps that you can buy at the hardware store often do not contain the components that are supposed to prevent radiation.”

But more potential sources of interference loom. For example, Elon Musk, known from Tesla and SpaceX, wants to bring tens of thousands of small satellites around the Earth to make fast internet possible everywhere via the StarLink network. Brentjens: “In terms of radio, we keep a close eye on whether the channels of the StarLink satellites are clean enough. As long as the satellites adhere to the precise transmission frequencies that have been internationally agreed upon, and nothing leaks, then things will probably go well.”

Yet Brentjens is not completely confident yet. He points to Motorola's Iridium communication satellites, which in his view are 'leaving the edges' with their transmitters: “Iridium is seriously bothering us. Because the transmitters of these satellites are poorly made, they also transmit in frequency channels that are protected.” But because the Iridium satellites are considered a national security interest by the US, little can be done about it in practice, Brentjens sighs.

In Europe, astronomers are now trying to join forces and make an overview of the threats these satellites can pose. “We also try to prevent sources of this type from being added,” says Brentjens. “We do this together with Agentschap Telecom, among others. For example, we have extra strict requirements for wind farms or solar parks that are installed near the LOFAR telescope.”

During his lecture at the RF Technology event 2020, this year in a digital edition, Brentjens will delve deeper into the matter surrounding disruptive radio signals and possible mitigations. But his closing words are clear: “Technology sometimes has unintended side effects. But I also want to emphasize that there are techniques that allow you to pinpoint where a fault is coming from. And many problems can be solved simply by talking to the owner of the source. That's something we do a lot: track down and talk. Because when you are with technicians, you often only look for technical solutions, while with some problems you can get much further with a social approach.”

Would you like to attend this lecture online? Register for free on the website of the RF Technology event.