SNIFFLES I: Intended Emission, Unwanted Emission, and Unintended Radiation from Low-Earth Orbiting Satellites Impacting Radio Astronomy from 1-26 GHz
Using the Mopra and ATCA radio telescopes, the SNIFFLES program conducted extensive observations of four low-Earth orbit satellite constellations, detecting thousands of instances of intended, unwanted, and unintended radio emissions across 1–26 GHz that frequently fall within protected radio astronomy bands and reach flux densities up to eleven orders of magnitude brighter than typical astronomical sources.
Original paper licensed under CC BY 4.0 (http://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
Imagine the universe as a giant, silent library where astronomers are the librarians. Their job is to listen to the faintest whispers from the edge of time—the radio waves left over from the Big Bang or the hum of distant stars. To hear these whispers, they need absolute silence. But recently, the library has been invaded by a fleet of noisy delivery drones. These aren't just any drones; they are thousands of low-Earth orbit satellites zooming around the planet, beaming internet to our phones and tablets. While they are great for sending memes and videos, they are terrible for listening to the cosmos. They don't just send their intended messages; they also leak "static" from their engines, computers, and power systems, creating a chaotic fog of radio noise that drowns out the universe's quiet secrets. This is the problem scientists call "radio frequency interference," and it threatens to make the library too loud to read the books.
This paper, titled "SNIFFLES," is like a team of very patient, very sensitive librarians who decided to go out and measure exactly how loud these satellites are. The researchers used a giant 22-meter radio dish in Australia (the Mopra telescope) and a smaller one nearby (ATCA) to track four major satellite groups: Starlink, OneWeb, Amazon Leo, and Guowang. They didn't just look for the satellites' main internet signals; they sniffed around for three specific types of noise: the signals the satellites want to send (intended emission), the signals they accidentally send just outside their allowed channels (unwanted emission), and the weird, random static coming from their internal electronics that they didn't plan to send at all (unintended radiation).
The team conducted over 4,600 observations, tracking satellites for nearly 376 hours. They found that these satellites are indeed making a lot of noise. They detected 2,345 instances of interference at more than 300 different frequencies. Some of this noise is the main internet signal, but a lot of it is the "unintended radiation" from the satellite's own guts—like the hum of a computer or a power converter. This noise is incredibly loud; in some cases, it is up to 11 orders of magnitude brighter than the faintest stars the astronomers are trying to study. This is so bright that it can completely overload the telescope's sensitive equipment, forcing scientists to throw away the data.
The researchers found that this noise isn't just a minor annoyance; it's a major problem. They detected these signals in frequency bands that are supposed to be protected for looking at the universe, including the area where scientists listen for the "OH line" (a specific chemical fingerprint in space) and other critical zones. For example, at 2700 MHz, they found this unwanted radiation in 76.9% of the observations for a specific version of the Starlink satellite. The paper concludes that as more satellites are launched, the sky is becoming so noisy that it is becoming nearly impossible for radio astronomers to avoid pointing their telescopes at these satellites. The authors suggest that while satellite companies are trying to fix this, the current rules aren't enough to stop the noise from drowning out the universe, and new regulations are needed to protect the "quiet zones" of the radio spectrum.
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