What we know so far: A network of classified defense satellites built by SpaceX is transmitting radio signals on frequencies typically reserved for the opposite direction of communication, a practice that may violate international radio standards. Signals traced to SpaceX's Starshield constellation – a government-operated system that extends the company's commercial Starlink technology into military use – have been detected broadcasting toward Earth within a section of the spectrum normally designated for uplink transmissions from the ground to satellites. The International Telecommunication Union designates the 2025 – 2110 MHz band exclusively for Earth-to-space communications.
The downlink activity was first detected not by a government agency, but by Scott Tilley, an amateur satellite tracker in British Columbia known for uncovering signals from secretive spacecraft. Tilley says the emissions appear to originate from Starshield satellites and may pose a risk of interference with other systems operating in nearby frequency bands.
"Satellites in neighboring orbits could pick up unintended commands or fail to respond correctly to legitimate ones," Tilley told NPR.
Independent experts who reviewed the findings say interference is plausible, though the severity of the impact remains unclear. "I think it is definitely happening," said Kevin Gifford, a University of Colorado Boulder professor who studies radio-frequency management in space systems. "Whether it's causing actual disruption is still an open question."
Both SpaceX and the National Reconnaissance Office (NRO) – the US agency overseeing Starshield's operations – declined NPR's requests for comment.
Tilley says he stumbled upon the unusual signals unintentionally while conducting unrelated observations. Monitoring from his home setup in British Columbia, he was recalibrating his equipment when his receiver began scanning a section of the spectrum that's normally quiet.
"It was just a clumsy move at the keyboard," he said. "I was working in the wrong band, the wrong antenna, and suddenly I saw something that shouldn't be there."
By regulation, the 2025 – 2110 MHz range is reserved for transmitting data from Earth-based stations to satellites, not the other way around. Yet Tilley recorded a persistent signal descending from space, occupying part of that band where no downlink should exist.
He captured the data and compared it against a global database maintained by amateur observers who track satellite orbits using telescopes and radio software. When he cross-referenced the signal's timing and trajectory, one name stood out: Starshield.
Starshield operates as the classified counterpart to SpaceX's Starlink broadband constellation, which delivers high-speed internet service around the world. While Starlink's network relies on high-frequency bands suited for large volumes of data transfer, Starshield communicates in lower frequencies more consistent with narrowband transmission.
Public information about the system remains limited, but government procurement documents show that the US has invested more than $1.8 billion in Starshield. According to SpaceX, the network supports both Earth observation and secure communications for defense and intelligence purposes.
Since May 2024, the National Reconnaissance Office has launched 11 batches of Starshield satellites, describing the effort as part of a "proliferated system" designed to enhance resilience and reduce latency in military data relay. "With hundreds of small satellites on orbit, data will be delivered in minutes or even seconds," the agency has stated publicly.
Tilley says he has now logged signals from roughly 170 Starshield satellites, all transmitting within the 2025 – 2110 MHz band. The precise transmission frequencies vary between spacecraft and appear to shift over time.
The purpose of these transmissions remains unclear. The lower-frequency band used by Starshield cannot deliver broadband data comparable to Starlink's high-speed connections; at best, Tilley estimates, it could support throughput similar to early 3G mobile networks.
He believes the use of this uplink-only band might be deliberate – a tactic to make Starshield's downlinks less conspicuous. The frequency-hopping behavior, he adds, could further obscure the network's activity from outside observers.
Gifford offers another explanation. He suggests SpaceX may have chosen the band simply because it is relatively quiet. "Those frequencies are usually dark," Gifford said. "SpaceX may have decided to use them first and deal with regulatory questions later."
So far, there have been no public reports of interference affecting other satellite operators. "If it were causing major disruptions, someone would have raised the issue by now," Gifford added.
Still, Tilley argues the international satellite community should be aware of what's occurring. "These are classified objects using nonstandard frequencies," he said. "Their transmissions could affect other legitimate uses of space, even if unintentionally."
SpaceX's classified Starshield satellites are broadcasting on restricted frequencies
