RF Sensing Satellites Explained: HawkEye 360, Kleos, Unseenlabs, and the $24B Spectrum Intelligence Market

Radio frequency (RF) sensing satellites detect, characterize, and geolocate radio emissions from terrestrial, maritime, and airborne sources from low Earth orbit. The category is a relatively recent commercial entrant — operating at meaningful scale only since the late 2010s — but has rapidly become one of the most strategically important intelligence collection layers for U.S., allied, and partner governments. HawkEye 360's April 2026 IPO filing brings public-market visibility to the category for the first time, and provides an opportunity to map the broader RF sensing market: how the underlying technology works, who the leading operators are, what the use cases look like, and why the prospectus's $24 billion current TAM projection is plausible.

How RF Sensing Works

RF sensing satellites use sensitive receivers to detect radio emissions across a wide frequency range — typically including VHF, UHF, L-band, S-band, C-band, X-band, and Ku-band, with specific operators emphasizing different bands depending on their target use cases. To geolocate the emitter, RF sensing constellations use multilateration: by detecting the same emission from multiple satellites simultaneously and measuring the very small differences in arrival time, the constellation can triangulate the emitter location to within a few kilometers (or better with sufficient geometry and signal characteristics). The same multilateration approach that GPS uses to position a receiver, RF sensing constellations use to position transmitters. The output is a stream of geolocated radio emission events that can be filtered, classified, and integrated into broader intelligence products.

The strategic value comes from what RF sensing reveals that other modalities cannot. A vessel that turns off its AIS transponder to evade tracking is invisible to AIS-based maritime intelligence, but its other radio emissions (radar, communications, navigation aids) are still detectable to RF sensors in orbit. A military exercise in a remote location may be invisible to optical satellites obscured by weather or geometry, but its electronic emissions are detectable across broad areas. A communications relay or jamming source can be precisely geolocated even when there is nothing visible at the location to indicate its presence. These types of intelligence products are uniquely valuable to defense and intelligence customers operating in environments where adversaries actively seek to defeat optical and radar collection.

The Leading Commercial RF Sensing Operators

HawkEye 360 is the largest and most established commercial RF sensing operator, with more than 30 satellites on orbit (most recently Cluster 14), $98.7 million in 2025 revenue, and dominant positioning across U.S. and allied government customer segments. Unseenlabs, the French commercial RF sensing operator, has built a substantial maritime-focused constellation and serves European, Asian, and U.S. defense and government customers, with particular strength in maritime domain awareness use cases. Kleos Space — formerly an ASX-listed RF sensing company that operated through a difficult phase — represents the cautionary case for the category, demonstrating that operational and commercial execution matter as much as the underlying technology. Spire Global operates RF sensing capabilities as part of its broader Lemur cubesat constellation, providing complementary capability to its weather, maritime, and aviation data products. A handful of smaller and emerging operators round out the commercial competitive set, and several adjacent military and intelligence-services contractors deliver RF analytics from in-house or partner-owned collection systems rather than operating commercial constellations themselves.

Use Cases: Maritime, Defense, and Beyond

RF sensing use cases span several recognizable categories. Maritime domain awareness is one of the most established: detecting vessels engaged in dark fishing, sanctions evasion, or other illicit maritime activity (when AIS-based tracking is defeated by transponder spoofing or shutoff). Defense intelligence (electronic order of battle, exercise monitoring, weapons system fingerprinting) is the largest revenue category by value, anchored by the U.S. Department of Defense, intelligence community, and allied counterparts. Crisis monitoring and humanitarian applications use RF sensing to identify communication patterns in disaster zones, conflict areas, or remote regions where other intelligence sources are unavailable. Spectrum monitoring (for telecoms, regulators, and infrastructure operators) is an emerging commercial use case that the HawkEye 360 prospectus suggests provides longer-term commercial growth optionality beyond the current government-anchored revenue mix. Across all of these use cases, the consistent theme is that RF sensing reveals activity that other sensing modalities miss — making it a near-mandatory layer in any modern multi-source intelligence architecture.

The $24B-to-$34B TAM

HawkEye 360's prospectus estimates the current TAM for global RF spectrum exploitation at approximately $24 billion, excluding commercial opportunities, with expected expansion to approximately $34 billion by 2030. The drivers HawkEye 360 calls out — expansion in the number of sensors across domains (ground, airborne, space), growth in support services (analytic services, mission integration), and increasing government demand for contractor-sourced RF data — are consistent with the broader pattern of government intelligence customers shifting from in-house collection to commercial-source augmentation. The TAM excludes commercial customers entirely, which is conservative; the maritime-insurance, infrastructure-monitoring, telecoms-spectrum-monitoring, and adjacent commercial categories collectively represent a meaningful additional opportunity that operators with the right go-to-market positioning can develop over time.

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