Unencrypted Satellites Reveal The Power Of Narrow Optical Links

By John Oncea, Editor

UCSD/UMD researchers found sensitive satellite data unencrypted; optical links offer narrow, secure beams, highlighting photonics’ role in protecting transmissions.

A research team from the University of California, San Diego (UCSD) and the University of Maryland (UMD) recently revealed a startling reality: vast amounts of sensitive satellite communications are being transmitted in the clear, according to Wired.

Using roughly $800 in off-the-shelf equipment, the researchers intercepted communications from geostationary satellites, uncovering unencrypted data ranging from cellular calls and text messages to corporate emails, infrastructure telemetry, and even military communications. According to the University of Maryland, this discovery underscores the vulnerability of satellite links, particularly those that rely on legacy broadcasting approaches.

Inside The Study

Over a period of three years, the team installed a modest parabolic dish on a university rooftop in La Jolla, CA, coupled with low-cost receivers and open-source signal processing software. Their observations were limited to roughly 15 percent of global geostationary Ku-band transponders visible from that location, yet even within this partial view, the scope of unencrypted data was significant.

Voice calls and text messages from major carriers in the United States and Mexico were captured, corporate communications, including emails and inventory records, were visible, and telemetry from critical infrastructure, such as electrical utilities, was transmitted in plain text, according to UCSD. Remarkably, some military and law-enforcement communications were also intercepted, revealing positions of aircraft, ships, and other operational information.

The findings illustrate that many satellite systems still rely on a model of “security through obscurity.” These systems, according to Gizmodo, were designed under the assumption that transmissions would not be intercepted.

In practice, however, modest equipment and widely available signal processing tools allow observers to extract sensitive data with relative ease. While encryption has been added to some networks following disclosure, many links remain vulnerable, demonstrating that the risk is systemic rather than isolated.

A Photonics Perspective

From a photonics standpoint, the study raises fundamental questions about the propagation and confinement of optical signals in satellite communications. One of the core challenges in designing secure optical links is the control of beam divergence and footprint.

Traditional geostationary satellite links, particularly in the radio-frequency spectrum, often utilize wide-area broadcast beams to cover large regions, a design choice that makes interception feasible even with limited equipment. In the optical domain, narrow-beam free-space links offer a striking contrast. By focusing energy into tightly confined beams, the probability of interception is dramatically reduced.

Optical communications also enable significantly higher data rates than legacy RF systems while maintaining low divergence angles, which is critical for both throughput and security. Free-space optical (FSO) links between satellites or from satellites to ground stations can achieve footprints that are orders of magnitude smaller than comparable RF beams.

The research highlights the advantages of such architectures, particularly as the proliferation of high-throughput satellites, low-earth-orbit constellations, and optical inter-satellite links increases the potential attack surface for legacy or misconfigured RF links.

The study also underscores the importance of physical-layer security in optical communications. Unlike RF systems that rely primarily on cryptography at higher layers, optical systems can combine end-to-end encryption with inherently secure propagation.

Narrow divergence, line-of-sight alignment, and adaptive beam tracking mean that even if data is encrypted, the energy is largely confined to intended paths. Emerging technologies such as laser communication terminals (LCTs), adaptive optics for ground-based stations, and quantum key distribution over optical links further enhance both the bandwidth and the confidentiality of satellite communications.

In addition to beam confinement, atmospheric effects play a critical role in optical satellite links. While turbulence, scattering, and absorption can degrade link quality, they also limit unintended interception at distances outside the direct line of sight.

Careful design of wavelength, divergence, and receiver aperture can mitigate loss while maximizing signal confinement, effectively creating a physical barrier to eavesdropping. This is a unique advantage of photonics over legacy RF satellite communications, where wide-beam transmissions propagate across entire continents and oceans.

Rethinking Security, Infrastructure, And Monitoring

The UCSD/UMD study reveals that the widespread assumption that satellites are “secure by distance” is no longer valid. Even with GEO satellites broadcasting over thousands of miles, modest ground stations with relatively simple equipment are sufficient to capture sensitive transmissions. The findings highlight the need to reconsider link design, propagation, and security assumptions, particularly as satellites increasingly support global networks carrying personal, corporate, and governmental data.

Moreover, the research emphasizes the vulnerability of legacy satellite infrastructure. Many operational links, even in critical infrastructure, still rely on protocols that predate modern encryption standards. The lack of physical-layer security means that even with cryptography, the broad propagation footprint increases the probability of signal interception, as metadata and traffic patterns can be observed.

Optical links, with their narrow beams and line-of-sight requirements, inherently reduce these risks. Future satellite deployments that replace or complement RF links with optical communications will benefit from both higher bandwidth and reduced exposure to interception.

The implications for the evolution of satellite networks are profound. Non-geostationary constellations in low Earth orbit (LEO) are increasingly adopting optical inter-satellite links to achieve high data throughput, reduce latency, and maintain network resilience. In these systems, narrow-beam optical communications allow satellites to relay data across the constellation while minimizing leakage outside the intended path. Ground-based optical stations, combined with precise pointing and tracking, further confine transmissions. These design choices represent a decisive advantage in maintaining confidentiality and controlling the propagation of sensitive signals.

The study also brings into focus the need for continuous monitoring and auditing of satellite links. While some networks have implemented encryption and mitigated vulnerabilities following the study, many remain exposed. The broader message is that the physics of signal propagation cannot be ignored when considering the security of satellite communications. Photonics-based links, whether in GEO, MEO, or LEO, offer a tangible path to controlling signal footprints, reducing exposure, and enhancing overall system security.

SATCOM Is Only As Secure As The Propagation Path

The UCSD/UMD findings serve as a clear demonstration that satellite communications are only as secure as the propagation path and physical confinement of the signal. While legacy RF systems remain vulnerable to interception, optical satellite links offer intrinsic advantages in beam control, confinement, and line-of-sight security. By leveraging narrow divergence, adaptive optics, and laser-based communications, future satellite networks can transmit sensitive data at high speed while dramatically reducing the risk of eavesdropping.

As the global reliance on satellite communications grows — for telecommunications, internet backhaul, remote sensing, and critical infrastructure — the lessons of this research highlight the importance of designing security into the physical layer. Optical systems provide the tools to do so, combining the advantages of high bandwidth, low divergence, and adaptive beam management. The age of “Don’t Look Up” — assuming no one will intercept GEO broadcasts — must give way to the era of “Can’t Look Up,” where photons themselves define the boundaries of security.