RF and signal monitoring
The radio spectrum, mapped from orbit.
Ships turn off their transponders. They cannot turn off physics.AIS dark vessel detection from orbit
Spaceborne AIS captures what vessels choose to broadcast; SAR captures what is actually there. The gap between those two layers is where dark vessels live.
Spire Global AISexactEarth spaceborne AISSentinel-1 SAR (C-band, ESA)
Jammers silence receivers below. They cannot silence the sky.GNSS jamming zone mapping from space
Deliberate GNSS jamming raises the L-band noise floor across wide areas. Spaceborne RF receivers can detect, geolocate and map those elevated noise zones in near-real-time, giving governments and operators a picture that no ground network alone can provide.
Spire Global GNSS-RO / GNSS-reflectometry constellationHawkEye 360 RF-monitoring constellationGAL-EGNOS RIMS ground network (reference / ground truth)
Vessels report one position. Physics places them somewhere else entirely.GNSS spoofing event detection and attribution
GNSS spoofing displaces reported positions while leaving a physical trace detectable by SAR and multi-constellation signal analysis. This page covers detection methods, documented incidents, and honest limits.
Spire Global AIS constellationSentinel-1 SAR (ESA Copernicus)HawkEye 360 RF monitoring constellation
Radars announce themselves. Satellites are listening.Radar emitter geolocation from low Earth orbit
Passive RF-sensing satellites can fix the position of ground-based and shipborne radar transmitters without illuminating them, using time- and frequency-difference-of-arrival geometry across multi-satellite formations. Accuracy, revisit and ambiguity limits depend heavily on constellation geometry and emitter behaviour.
HawkEye 360 RF constellationKleos Space RF constellationSpire Global RF payload (LEMUR-2)
The signal reaches two satellites. The geometry does the rest.Satellite communications interference source location
Uplink interference, whether accidental cross-polarisation or deliberate jamming, can be geolocated by comparing the time and power differences of the same signal arriving at adjacent satellites. This page covers the physics, the published ITU procedures, and the practical limits of the method.
Intelsat IntelsatOne Flex interference monitoring networkSES network operations centre monitoringHawkEye 360 RF geolocation constellation
The ground sees one tower. The orbit sees the whole band.VHF and UHF spectrum occupancy surveys from orbit
Wideband SDR payloads in LEO measure how densely VHF and UHF spectrum is occupied across entire regions in a single pass, revealing usage patterns no terrestrial monitor network can replicate at comparable scale.
HawkEye 360 RF constellationSpire Global LEMUR-2 SDR payloadNORSAT-1 VHF/AIS payload
Aircraft vanish from radar at the coastline. Physics disagrees.ADS-B aircraft tracking from space
LEO satellites receive 1090 MHz ADS-B transmissions to track aircraft over oceans and polar regions where ground radar cannot reach. Aireon, hosted on Iridium NEXT, is the only fully operational global system with published performance data.
Aireon (Iridium NEXT hosted payload)Spire Global ADS-BexactEarth ADS-B (now part of exactEarth / Spire portfolio)
A beacon transmits once. The satellite has milliseconds to hear it.EPIRB and PLB signal detection from orbit
The Cospas-Sarsat system turns 406 MHz distress transmissions into geolocated alerts via LEO Doppler processing and MEO near-instantaneous relay. Understanding its geometry, latency and gaps is essential for any government operating search-and-rescue coordination.
Cospas-Sarsat LEOSAR (Low-Earth Orbit Search and Rescue)Cospas-Sarsat MEOSAR (Medium-Earth Orbit Search and Rescue)Cospas-Sarsat Return Link Service (RLS)
The transmission lasts two seconds. The geometry lasts forever.Push-to-talk VHF/UHF radio geolocation from space
Short-duration VHF/UHF push-to-talk radios are hard to fix from orbit precisely because they are brief and unpredictable. Multi-satellite TDOA/FDOA geometry can locate them, but only when the intercept probability problem is solved first.
HawkEye 360 RF clusterKleos Space RFSpire SDR payload
Ground radars corrupt SAR imagery. The corruption is also data.Radio frequency interference mapping in SAR imagery
Ground-based transmitters in or near the C- and L-band SAR operating windows inject bright streaks and range-ambiguity artefacts into satellite radar imagery. Characterising that contamination reveals both where emitters sit and how to suppress them.
Sentinel-1 (ESA, C-band, 5.405 GHz)ALOS-2 PALSAR-2 (JAXA, L-band, 1.2578 GHz)RADARSAT-2 (MDA, C-band, 5.405 GHz)
A vessel can silence its AIS. It cannot silence its radar.Shipborne radar activity monitoring from orbit
Passive detection of X-band and S-band navigation radar emissions from LEO satellites can confirm ship presence and operational status independently of AIS, exposing vessels that are dark by choice rather than by accident.
HawkEye 360 RF constellationKleos Space RF constellationSpire Global RF payload (LEMUR-2 satellites)
Operators publish coverage maps. Orbital receivers check the physics.Terrestrial LTE and GSM coverage mapping from LEO
Spaceborne SDR receivers detect LTE and GSM downlink emissions beyond their intended service areas, providing an independent audit of operator coverage claims and flagging unplanned cross-border signal spillage.
HawkEye 360 ClusterSpire LEMUR-2 SDR payloadNORSAT-1
A pirate transmitter cannot hide its carrier from orbit.Illegal and unlicensed broadcast transmitter detection
Spaceborne wideband receivers can detect and geolocate HF, VHF, and FM broadcast transmitters operating outside licensed frequency, power, or geographic limits. This page explains the physics, the sensors, and the hard limits regulators need to understand before commissioning a campaign.
HawkEye 360 RF constellationSpire Global SDR payloadTechDemoSat-1 SDR (historical)
A vessel can lie about its position. Its radar echo cannot.AIS message spoofing and manipulation pattern analysis
Fabricated AIS messages, phantom vessels and MMSI cloning are detectable by cross-referencing spaceborne AIS reception with SAR imagery and RF geolocation. Temporal and geometric inconsistencies in message sequences expose manipulation that shore-based AIS alone cannot resolve.
Spire Global AIS (LEO constellation)exactEarth satellite AISSentinel-1 SAR (C-band, ESA Copernicus)
The ionosphere bends HF signals. Orbit sits above the bend.HF skywave emitter monitoring from low Earth orbit
High-frequency transmissions bounce off the ionosphere, confounding ground-based direction-finding. Spaceborne receivers intercept the direct upward wave before refraction, enabling geolocation that ground networks cannot reliably achieve alone.
HawkEye 360 Cluster satellitesSpire Global SDR payload (LEMUR-2 satellites)TechDemoSat-1 SDR (historical, SSTL/UK, 2014–2018)
Drones fly low. Their radio links still reach orbit, barely.Unmanned aerial vehicle RF control link detection from orbit
Spaceborne RF receivers can intercept UAS command-and-control and video downlink transmissions, but the physics is unforgiving. This page sets out what is genuinely detectable, under what conditions, and where the method runs out of road.
HawkEye 360 ClusterSpire Global SDR PayloadKleos Space RF Reconnaissance
Your GNSS receiver is misbehaving. Was it the ionosphere or someone with a box?Ionospheric scintillation monitoring via GNSS from LEO
Plasma bubbles in the ionosphere cause GNSS signal amplitude and phase fluctuations that can ground aircraft, disrupt precision agriculture and mimic jamming. LEO radio-occultation constellations now map scintillation events globally, giving operators the evidence to tell space weather from hostile interference.
Spire GNSS-RO constellationCOSMIC-2 / FORMOSAT-7PlanetiQ GNSS-RO
Vessels go dark on AIS. Their radars keep talking.Fishing vessel activity inference from RF fingerprinting
Passive RF detection from low Earth orbit can locate fishing vessels that have disabled or never carried AIS, by capturing navigation radar pulses, VHF traffic, and fish-finder emissions. Vessel-type inference from RF signatures alone is probabilistic, not definitive, and this page explains exactly where the confidence holds and where it does not.
HawkEye 360 RF constellationKleos Space RF constellationSpire Global AIS and GNSS
The waveform is encrypted. The fact of transmission is not.Military tactical datalink emission detection from orbit
Spaceborne wideband RF sensors can detect the presence and approximate location of military tactical datalink emissions such as Link 16 without decrypting them. This page covers what the open literature says about detection physics, geolocation accuracy, revisit limits, and why the application sits in legally and diplomatically sensitive territory.
HawkEye 360 RF constellationKleos Space RF constellationSpire Global SDR payload
A silent platform is not a safe platform. Silence is the signal.Offshore platform and subsea cable RF activity monitoring
Fixed offshore infrastructure emits predictable RF signatures. When those signatures change or disappear, spaceborne RF monitoring can catch it before a vessel inspection ever reaches the site.
HawkEye 360 RF constellationSpire SDR (software-defined radio) constellationSpire AIS (space-based AIS)
The transmitter went silent. Only a satellite noticed.LORAN and Chayka navigation transmitter monitoring from orbit
LEO RF payloads can detect 90–110 kHz LF skywave emissions from LORAN-C and Chayka stations, revealing operational status, pulse-timing drift, and unexpected activations that ground-based monitoring networks miss.
HawkEye 360 Cluster SatellitesSpire LEMUR-2 RF PayloadPublished LORAN-C / Chayka Monitoring Literature (US Coast Guard, IALA)
An aircraft goes down. The signal is instant. The satellite is not.Aviation ELT distress signal detection from LEO
406 MHz Emergency Locator Transmitters alert the Cospas-Sarsat constellation when aircraft crash or declare distress. LEO geometry, false-alarm rates and terrain masking all shape how quickly that alert becomes a rescue.
Cospas-Sarsat MEOSAR payloads (GPS, GLONASS, Galileo, BeiDou SAR instruments)Cospas-Sarsat LEOSAR (NOAA-15, NOAA-18, NOAA-19, MetOp-A/B/C)Spire LEMUR-2
GNSS signals were never aimed at the ocean. The ocean answers anyway.Ocean surface wind speed retrieval via GNSS reflectometry
Reflected GPS and Galileo signals carry a measurable imprint of ocean roughness. GNSS-R turns that accidental return into wind speed and wave height at roughly 25 km resolution, globally, with no transmitter of your own.
NASA CYGNSS constellationESA TechDemoSat-1 (TDS-1)Spire Global GNSS-R payload
The signal is anonymous. The physics of arrival time is not.Uplink interference geolocation using TDOA and FDOA from GEO pairs
When a terrestrial emitter interferes with a GEO satellite uplink, time and frequency differences across two or more satellites can triangulate its position. This page explains the geometry, the error sources, and what commercial services can and cannot resolve.
Intelsat Geolocation Service (GEO fleet)Kratos Monics platformSES Interference Management Service (GEO fleet)
Declared or not, active facilities talk. Orbit listens.RF activity signature monitoring near nuclear facilities
Space-based RF sensing can characterise emission patterns around nuclear sites, flagging state changes that optical and SAR imagery alone may miss. Ambiguity is real; multi-source corroboration is mandatory.
HawkEye 360 cluster satellitesSpire LEMUR-2 RF payloadSentinel-1 SAR (corroborating layer)
GSM-R interference grounds trains. Satellites find it before inspectors do.Railway signalling RF interference detection from LEO
LEO RF monitoring satellites can scan entire national rail corridors for GSM-R interference in hours, not weeks. Ground survey teams are fast at confirmation; they are slow at discovery.
HawkEye 360 cluster satellitesSpire LEMUR-2Generic LEO TDOA/FDOA formation
VDES promises to replace AIS. Almost nobody is transmitting yet.VHF Data Exchange System (VDES) signal monitoring from orbit
VDES is the IMO-standardised successor to AIS, offering higher data rates and two-way satellite links in the 157–158 MHz band. Space-based receivers can already track adoption rates, coverage gaps, and protocol compliance, even though operational deployments remain sparse in the mid-2020s.
Kongsberg / NORCE VDES prototype payload (NorSat-3 and related)Spire LEMUR-2 multi-mission CubeSatITU-R M.2092 compliant ground reference receivers
The radars watching space can themselves be watched from space.Ground-based space surveillance radar emission monitoring from orbit
High-power ground-based space surveillance radars emit signals detectable by RF receivers in LEO. Characterising their waveforms, frequencies, and duty cycles from orbit reveals operational tempo and mode changes, with significant caveats around classification and ambiguity.
HawkEye 360 cluster satellitesSpire LEMUR-2US Space Fence (Lockheed Martin / USAF, Kwajalein Atoll)
Radar stops at the coastline. ACARS messages do not.ACARS aeronautical datalink monitoring from LEO
Space-based receivers can collect VHF ACARS, HFDL, and VDL Mode 2 traffic far beyond ground-station range, filling the oceanic gaps that radar and ATC simply cannot reach. This page explains the physics, the variants, the decode limits, and what the data is actually good for.
Spire LEMUR-2HawkEye 360 cluster satellitesAireon ADS-B (cross-validation reference)
Jammers silence drones. They cannot silence themselves.Counter-UAS jammer and RF suppressor geolocation from orbit
Ground-deployed counter-UAS jammers broadcast across ISM bands that LEO RF-monitoring satellites can detect and geolocate. This page explains the physics, the methods, and the honest limits of doing that from orbit.
HawkEye 360 cluster satellitesSpire LEMUR-2TDOA/FDOA multi-satellite geometry (general method)
Aircraft cross the Arctic in silence. Space-based ADS-B ends that.ADS-B coverage gap characterisation over polar routes
Ground radar and VHF radio fade out above roughly 78°N. Space-based ADS-B receivers on Iridium NEXT and Spire LEMUR-2 satellites now quantify exactly where surveillance gaps remain, and by how much, informing ICAO performance-based requirements for polar route approval.
Aireon (Iridium NEXT hosted payload)Spire LEMUR-2 ADS-B1090 MHz Extended Squitter (1090ES) signal standard
Encrypted traffic is invisible. The uplink itself is not.Tactical military SATCOM uplink band occupancy monitoring
Space-based RF monitoring of the 292–317 MHz UHF MILSATCOM uplink band can characterise spectrum occupancy, flag unauthorised emitters and locate interference sources, without decoding a single protected message.
HawkEye 360 cluster satellitesSpire LEMUR-2US DoD UHF Follow-On (UFO) satellite system
A ship can lie about its position. Its radio cannot.Correlation of AIS tracks with VHF voice radio activity from ships
Space-based VHF receivers can geolocate maritime voice transmissions to 5–15 km and compare that fix against AIS-declared positions. Where the two diverge, fraud is the most likely explanation.
HawkEye 360 cluster satellitesSpire LEMUR-2AIS Class A transponders (vessel-declared)
GNSS signals were built for navigation. Wet soil gives them away.Soil moisture retrieval from GNSS reflectometry
Reflected GPS and GLONASS signals carry a measurable imprint of surface dielectric constant, allowing near-surface volumetric soil moisture to be retrieved at basin scale from low Earth orbit, without an active radar transmitter.
NASA CYGNSS constellation (8 microsatellites)Spire Global GNSS-R payload (LEMUR-2 satellites)ESA SMOS (Soil Moisture and Ocean Salinity)
The universe emits. Constellation downlinks drown it out.Interference into radio astronomy protected bands from LEO
ITU-protected radio astronomy bands are being measurably degraded by LEO constellation emissions and terrestrial leakage. This reference covers how interference is characterised, quantified and attributed using ground observatory monitors and space-based RF sensors.
Green Bank Observatory RFI monitoring systemITU-R RA.769 threshold frameworkESA Sentinel-1 SAR (C-band, 5.405 GHz)
A vessel can lie on AIS. Its radar cannot lie about its physics.Shipborne radar type classification from spectral signatures
Space-based RF receivers can classify the type of radar fitted to a vessel by measuring pulse repetition frequency, bandwidth, and carrier frequency from LEO, providing an independent check on AIS-declared vessel type.
HawkEye 360 cluster satellitesSpire LEMUR-2Generic space-based ELINT receivers (published literature context)
Targets move. The signals they disturb do not lie.Passive bistatic radar detection using LEO satellite signals of opportunity
Passive bistatic radar uses LEO satellite downlinks as uncooperative illuminators to detect aircraft, ships and ground targets without emitting a single watt. The technique is experimentally promising but operationally immature, and the signal-to-noise arithmetic is brutal.
GNSS constellations (GPS L1/L2, Galileo E1/E5, GLONASS L1/L2)Iridium NEXT (66 satellites, L-band ~1.6 GHz)CYGNSS (8 microsatellites, GPS L1 C/A reflectometry)
Broadcasters file for licences. Clandestine transmitters do not.DAB and DVB-T digital broadcast signal monitoring from orbit
Spaceborne RF receivers can detect, geolocate and fingerprint DAB and DVB-T transmitters by exploiting their OFDM pilot-tone structure, enabling regulators to verify compliance, resolve cross-border interference disputes and identify unlicensed transmitters without ground-based inspection.
HawkEye 360 cluster satellitesSpire STRATOS RF payloadITU/NOAA interference monitoring filings
Ships go silent on AIS. Their satellite phones keep talking.L-band mobile satellite service congestion and occupancy monitoring
Spaceborne RF scanners can measure power spectral density across the 1–2 GHz L-band from LEO, exposing congestion, unauthorised access and interference events in mobile satellite service allocations that ground-based monitoring consistently misses.
HawkEye 360 cluster satellitesSpire STRATOS RF payloadInmarsat published interference reports
Aircraft broadcast their position. They cannot broadcast the truth.Mode S extended squitter anomaly and spoofing detection from LEO
Space-based receivers collecting Mode S extended squitter messages from multiple orbital vantage points can cross-validate message authenticity using TDOA geometry, kinematic physics and ICAO address consistency, catching spoofed or manipulated ADS-B traffic that ground networks routinely miss.
Aireon space-based ADS-B (Iridium NEXT)Spire aviation payloadEUROCONTROL MUAC Mode S surveillance radar
Canopy hides an emitter from ground sensors. Orbit does not care.P-band and UHF foliage-penetration emitter detection from orbit
Low-frequency emitters in dense forest are effectively invisible to ground direction-finding networks, yet their signals propagate upward with little canopy loss. Spaceborne RF receivers at LEO can intercept these emissions and geolocate sources using time-difference-of-arrival across clustered satellites.
HawkEye 360 cluster constellationSpire STRATOS RF payloadESA BIOMASS P-band SAR (published design)
A handset stays still. The satellite does not.Satellite phone uplink geolocation from LEO intercept geometry
Passive intercept of L-band and S-band satellite phone uplinks from LEO platforms can geolocate a transmitting handset to within a few kilometres by exploiting the Doppler curve and time-difference geometry produced by a fast-moving receiver against a stationary emitter.
HawkEye 360 cluster constellationSpire STRATOS RF payloadIridium NEXT hosted payload capacity
Weather radars protect lives. They also pollute spectrum nobody budgeted for.Meteorological wind profiler radar emission mapping from orbit
Ground-based wind profiler radars operating between 400 and 1300 MHz cause documented interference into adjacent mobile and satellite bands. Spaceborne RF sensors can map their locations, duty cycles and emission patterns without ground access.
HawkEye 360 cluster satellitesSentinel-1 SAR (C-band, 5.405 GHz)Spire Global LEMUR-2 constellation
Ninety-seven percent of distress alerts are false. Telling them apart matters.False-alert discrimination for 406 MHz distress beacons from LEO
More than 97% of 406 MHz EPIRB and PLB activations processed by Cospas-Sarsat are false alerts. Spaceborne RF receivers can cross-check signal fingerprints, registration records and positional context to help rescue coordination centres triage faster.
Cospas-Sarsat MEOSAR payloads (GPS, GLONASS, Galileo)Cospas-Sarsat LEOSAR payloads (NOAA, MetOp, Sarsat LEO hosts)Spire STRATOS RF payload
OTHR systems paint half a continent. Their waveforms are harder to hide.Over-the-horizon radar waveform detection and classification from LEO
HF over-the-horizon radars broadcast distinctive chirp and FMCW signatures across thousands of kilometres of skywave path. LEO wideband receivers can detect, classify and schedule-track those emissions, within the real limits imposed by ionospheric geometry and networked emitter ambiguity.
HawkEye 360 cluster satellites (HF extension bands)Spire Global LEMUR-2 constellation (HF/VHF SDR payloads)ITU-R M.1462 coordination database (ground truth reference)
Ice does not transmit. It reflects, and that reflection carries elevation.Ice sheet surface altimetry via GNSS reflectometry from LEO
Reflected GNSS signals collected by nadir-pointing LEO antennas reveal ice-sheet surface elevation and roughness. Vertical precision reaches tens of centimetres over flat ice but degrades sharply over crevassed or heavily sastrugi terrain.
CYGNSS constellation (NASA)ESA HydroGNSSSpire GNSS-R payload
A base station can be silenced. Its absence is equally informative.Cellular base station RF mapping in conflict and denied-access zones
Spaceborne RF sensors can detect, geolocate and track the operational status of GSM, LTE and 5G NR base stations without ground access, turning signal presence or absence into intelligence about infrastructure destruction, relocation or deliberate suppression.
HawkEye 360 cluster satellitesSpire STRATOS wideband RF payloadITU BR IFIC frequency assignment database