Radio astronomers are facing a growing headache: interference from the increasing number of satellites orbiting Earth. The unexpected scale of this radio frequency (RF) disruption is prompting calls for stricter standards and better antenna design.
Satellite Signals Are Jamming the Cosmos
The proliferation of satellites in low Earth orbit is creating unexpected challenges for radio astronomy.
The “photobombing” of telescopes by satellites is well-known, but the impact on radio astronomy is only recently becoming fully apparent. Tudor williams, CTO of high-frequency RF communication company Filtronic, explained the core issue: signals bleeding over from satellite communications are disrupting sensitive observations.
What causes this radio interference from satellites? According to Williams, the problem stems from “side lobes” in antenna designs.These lobes unintentionally radiate signals in directions other than the intended target, potentially overlapping wiht frequencies used by radio astronomers.
“In a badly designed antenna,” Williams explains, “you get fairly strong lobes of signals that get sent in different directions.”
The issue isn’t a simple matter of regulatory oversight. Williams suggests that existing regulations may have been insufficient given the rapid deployment of large satellite constellations. “Maybe the regulations weren’t as stringent as they should have been at the start,” he says, “And as we start to get more data on this, we can obviously have more stringent guard bands and more stringent regulations going forward.” A “guard band” is a slice of radio spectrum designed to prevent signal leakage between channels.
While satellite designers strive for optimal performance,errors can occur,leading to unwanted spectral leakage. Authorities ultimately determine the acceptable level of interference.
Retrofitting existing satellites isn’t a practical solution,but Williams points to potential software-based improvements. “They can do updates to things like the waveforms,” he says. “The type of waveforms you’ve got through the amplifier has quite a big impact on spectral spreading. It’ll stress the amplifiers in different ways.” He suggests that optimizing these waveforms, even with existing hardware-potentially using AI-could reduce distortion.
“So you potentially could solve it from a baseband outlook.”
Beyond technical fixes, Williams believes market forces will encourage responsible behavior.”The more we see this happening,” he explains, “the more that will push back into satellite operators because they’ll be under pressure to behave. As they have to control their spectrum.”
Satellite operators also have a vested interest in maintaining good standing with regulatory bodies. Williams notes that license renewals could be jeopardized by excessive interference. “I think,” says Williams, “we need to have a co-existence of scientific missions and general broadband comms.”
Companies like SpaceX, with its starlink constellation, are designing satellites with a lifespan of approximately five years.This provides an possibility to incorporate improved hardware and software as regulations evolve. “Would there be cost implications if you have to control it [the signal] better?” muses Williams. “Yes. Problably.because it makes the design more complicated … volume manufacturing and lots of satellites can add quite a lot of cost in the process.”
while the visual impact of satellite constellations is readily apparent,the extent of RF interference has surprised many.According to Williams, “feedback into standards bodies will be pushed out to the satellite operators, and they’ll have to have better performance systems going forward.”
