SpaceX's Starshield Spy Satellites Caught Sending Signals in the Wrong Direction, Raising Spectrum Concerns

In the shadowy world of satellite surveillance, where classified orbits and secretive payloads define the mission, an accidental discovery has thrown a spotlight on a potential regulatory misstep. Scott Tilley, an engineering technologist and amateur radio astronomer from British Columbia, stumbled upon something extraordinary while tinkering with his backyard antenna setup: over 170 Starshield satellites—built by SpaceX for the US government's National Reconnaissance Office (NRO)—are beaming strong signals from space to Earth in a frequency band that's supposed to work the other way around.

The Starshield constellation, a militarized evolution of SpaceX's commercial Starlink network, is designed to supercharge the NRO's global surveillance capabilities. Launched in batches since 2023, these satellites orbit in classified paths, their exact purposes shrouded in secrecy. But Tilley's findings, detailed in a technical paper and first reported by NPR, reveal emissions in the 2025–2110 MHz S-band—a range internationally allocated by the International Telecommunication Union (ITU) for Earth-to-space uplinks and space-to-space links, not downlinks. From his location, Tilley confirmed signals from 171 out of 193 known Starshield satellites passing over Canada, the US, and Mexico, with the global constellation likely affecting other regions too.

An Accidental Revelation from a Seasoned Tracker

Tilley's discovery wasn't part of a targeted hunt. As he told Ars Technica, it stemmed from "a clumsy move at the keyboard" while resetting his equipment. Using a combination of omnidirectional and dish antennas, software-defined radios, and custom software, he captured wideband emissions up to 9 MHz wide with signal-to-noise ratios (SNR) of 10–15 dB—strong enough to be picked up by modest ground stations. Some signals even shifted frequencies day-to-day, exceeding 20 dB SNR.

This isn't Tilley's first rodeo. In 2018, he famously helped NASA rediscover a long-lost satellite from 2005. Now, his work on Starshield underscores a growing tension in orbital real estate: as low-Earth orbit fills with mega-constellations, spectrum management becomes a high-stakes game. Tilley's paper warns that these emissions could interfere with legitimate uplink signals to satellites, including NASA's science missions and NOAA's weather satellites, which rely on this band for tracking, command, and data relay.

Why This Band Matters—and Why It's Problematic

The 2025–2110 MHz band is a workhorse for space operations. In the US, it's used by federal agencies like NASA for controlling everything from the Hubble Space Telescope to the International Space Station, and by NOAA for environmental satellites that feed data to the National Weather Service. Non-federal users, such as TV broadcasters' electronic news gathering (ENG) trucks with satellite dishes, also operate here under strict rules limiting high-density mobile systems.

These ground-based systems are typically directional and terrestrial-focused, minimizing skyward interference risks. However, Starshield's downlinks are broadcasting broadly from orbit, potentially drowning out uplink commands to other satellites. Tilley explains: "If you’ve got a loud constellation of signals blasting away on the same frequencies, it has the potential to interfere with the reception of ground station signals being directed at satellites on orbit."

Experts like spectrum consultant Rick Reaser, with decades in Defense Department spectrum management, acknowledge the novelty but downplay immediate harm. "You would not see this unless you were looking for it," he notes, suggesting the signals are designed to fly under the radar. No public interference complaints have surfaced—from US broadcasters or agencies like the Canadian Space Agency (CSA), which reports no impacts on its missions. Yet, Tilley argues this addresses performance, not legality: domestic approvals don't excuse the lack of international coordination.

Secrecy vs. Transparency: A Classified Conundrum

At the heart of the issue is the opacity of US government spectrum use. The NRO likely cleared these emissions through the National Telecommunications and Information Administration (NTIA) on a non-interference basis—common for federal operations, where decisions stay classified. As Reaser puts it, "They say, ‘listen, if somebody reports interference, then you have to shut down.'" The FCC and NTIA declined comment, while SpaceX, acting as a contractor, didn't respond.

Northwestern professor Randall Berry agrees this is probably above-board domestically but flags international risks. ITU rules under Article 4.4 allow non-interference use but mandate coordination for global systems like Starshield. The CSA confirms no ITU filings for this network, and the ITU itself won't comment without a formal complaint from a national administration.

This secrecy extends to satellite registrations with the UN's Office for Outer Space Affairs (UNOOSA), listing Starshield vaguely as for "practical applications and uses of space technology." Tilley calls this a contradiction to the spirit of treaties, especially for military assets in massive constellations that blanket the globe.

Broader Implications for Space and Spectrum Governance

The Starshield saga mirrors global tensions. Tilley points to China's Guowang constellation, which uses non-allocated spectrum after ITU denial, proceeding unilaterally after consultation. By contrast, Canada's Sapphire satellite filed detailed ITU notices. As mega-constellations from the US, China, and others proliferate, Tilley warns of a "distorted" international framework where powerful nations sidestep coordination, risking an "orderly and predictable radio environment."

For developers and engineers building satellite tech, this raises practical concerns. Strong, predictable carriers from Starshield could inadvertently enable positioning, navigation, and timing (PNT) exploitation—useful in contested environments but a vulnerability if jammed or spoofed. NASA's increasing reliance on the band, amid spectrum pressures from commercial broadband, amplifies the stakes. A 2021 NTIA filing noted "dramatically increased demand," with even limited commercial launch uses requiring NTIA coordination to avoid "significant interference."

Tilley's call for "cooperative disclosure—without compromising legitimate security interests" strikes a balance. By sharing reproducible data, he's empowered others to verify and assess risks, alerting operators to monitor for subtle interference that might degrade commands without obvious failure.

In an era where space is the ultimate high ground, these errant signals remind us that even the stars aren't immune to earthly rules. As constellations grow denser, the line between innovation and interference blurs, demanding smarter governance to keep the cosmos connected—without the static.