How space data is sourced
Know the sensor before you trust the answer.
The ground moves millimetres. Radar notices before anyone else does.SAR interferometric surface deformation mapping
InSAR compares the phase of repeat SAR passes to map ground displacement at millimetre scale, revealing subsidence, uplift and fault creep invisible to optical sensors. Coherence, atmospheric delay and imaging geometry all shape what the technique can and cannot see.
Sentinel-1 (ESA)ALOS-2 PALSAR-2 (JAXA)ICEYE SAR constellation
Leaves reflect what they cannot hide from orbit.Multispectral vegetation index monitoring
Multispectral satellites measure how plant canopies absorb and reflect sunlight, revealing crop stress, biomass change and land-cover shifts weeks before they are visible to the eye. This page explains the physics, the band configurations of the main sensors, and the real limits imposed by cloud cover.
Sentinel-2 MSI (ESA)Landsat 8/9 OLI (USGS/NASA)Planet SuperDove
The ground radiates heat constantly. Clouds just decide when you can see it.Thermal infrared land surface temperature retrieval
Thermal infrared sensors measure emitted radiance from the Earth's surface, which is converted to land surface temperature through emissivity correction and atmospheric adjustment. Resolution, revisit and cloud cover set hard limits that no processing chain can overcome.
Landsat 8/9 TIRSECOSTRESS (ISS-mounted)ASTER TIR
Factories claim clean air. TROPOMI reads the column above them.Tropospheric nitrogen dioxide column mapping
TROPOMI on Sentinel-5P retrieves tropospheric NO2 columns daily at 3.5 × 5.5 km, exposing industrial point sources, shipping corridors and urban traffic patterns that ground monitors miss entirely.
Sentinel-5P TROPOMIOMI (Aura satellite, NASA)GEMS (GEO-KOMPSAT-2B, KMA)
Water looks blue. What it hides is written in its colour.Ocean colour and coastal water quality retrieval
Sentinel-3 OLCI, MODIS and VIIRS measure water-leaving radiance across visible wavelengths to derive chlorophyll-a, suspended matter and dissolved organics. This page explains the physics, the algorithms, and the hard limits that apply near coastlines.
Sentinel-3 OLCIMODIS AquaVIIRS SNPP / NOAA-20
Ships turn off their transponders. They cannot turn off physics.AIS vessel tracking and dark-ship detection
Space-based AIS receivers capture VHF transponder broadcasts from vessels worldwide, but gaps in that record are where the real intelligence begins. Cross-referencing AIS silence against SAR and optical detections exposes vessels that would prefer not to be seen.
Spire Maritime (LEO AIS constellation)exactEarth (SAT-AIS)Sentinel-1 SAR (ESA Copernicus)
Aircraft broadcast their position. Space finally listens.ADS-B aircraft surveillance from space
LEO satellites carrying 1090 MHz receivers decode ADS-B Out transmissions from aircraft anywhere on Earth, including oceans and polar regions where ground radar cannot reach. The technique extends global air traffic awareness but carries real latency and signal-collision constraints that buyers must understand before specifying it.
Aireon (hosted on Iridium NEXT)Spire Aviation ADS-BexactEarth ADS-B (now part of exactEarth / Spire portfolio)
Emitters announce themselves. Silence is not an option.RF emitter geolocation from space
Clusters of LEO satellites can fix the position of any radiating emitter using time and frequency differences of arrival, no cooperation required. Accuracy depends on constellation geometry, ephemeris quality, and signal duration.
HawkEye 360 cluster constellationKleos Space Scouting MissionUnseenlabs BRO constellation
The atmosphere bends radio waves. That bending is a thermometer.GNSS radio occultation atmospheric profiling
GNSS radio occultation turns GPS and GLONASS signals into vertical slices of the atmosphere, yielding temperature, pressure and humidity profiles with roughly 100 m vertical resolution and no need for calibration targets.
COSMIC-2 / FORMOSAT-7Spire GNSS-ROMetop GRAS (GNSS Receiver for Atmospheric Sounding)
Forests absorb carbon in three dimensions. Satellites finally measure it.Spaceborne lidar canopy height and forest structure
ICESat-2 and GEDI fire laser pulses through forest canopies and time the returning photons to map vertical structure at scales no passive sensor can reach. Each system has distinct geometry, sensitivity and coverage gaps that buyers must understand before committing to a monitoring design.
ICESat-2 ATLASGEDI (Global Ecosystem Dynamics Investigation)Sentinel-2 MSI (supporting layer)
Cities glow. The sensor records who turned the lights off.VIIRS day-night band nighttime light monitoring
The VIIRS Day-Night Band detects low-radiance visible and near-infrared emissions at 750 m nadir resolution, enabling electrification mapping, economic proxies, gas-flare monitoring and conflict damage assessment. Saturation, lunar contamination and a broken heritage link to DMSP-OLS are the limits every analyst must account for.
VIIRS DNB (Suomi-NPP)VIIRS DNB (NOAA-20)DMSP-OLS (heritage archive)
Clouds close airports. They do not stop radar.Commercial SAR rapid flood extent mapping
Synthetic aperture radar maps flood extent in any weather, day or night, by detecting the near-zero backscatter of smooth open water. Commercial constellations now cut revisit from days to hours, but wind and forest canopy introduce real ambiguities that analysts must account for.
ICEYE SAR constellationCapella Space SARSentinel-1 (ESA/Copernicus)
Buildings go up overnight. The question is whether you noticed.Very-high-resolution optical change detection
Sub-metre commercial optical imagery from Maxar, Airbus and Planet can resolve individual vehicles, construction equipment and structural damage. This page explains how change detection works, where it breaks down, and what the resolution-versus-revisit trade-off means in practice.
Maxar WorldView-3Airbus Pléiades NeoPlanet SkySat
Water moves. Radar pulses record exactly how much.Sentinel-3 radar altimetry for sea level and inland water
Sentinel-3 SRAL measures sea surface height, wave height and inland water levels using SAR-mode radar altimetry. This page explains the physics, the 27-day repeat cycle, and where the method breaks down.
Sentinel-3 SRALSentinel-6 Michael FreilichJason-3
A single frame misses the truck. A thirty-second clip does not.Video from space for transient activity detection
Commercial video satellites capture short clips at sub-metre resolution, revealing moving vehicles, vessel wakes and aircraft invisible in still imagery. Frame rate, footprint and data volume impose hard limits that any serious programme must plan around.
Planet SkySatSatellogic VideoSatBlackSky
Ships turn off their transponders. They cannot turn off physics.SAR-based ship detection and vessel classification
Synthetic aperture radar detects vessels by their radar cross-section regardless of cloud, darkness or deliberate AIS silence. Polarimetric signatures and object geometry then allow classification by vessel type, with honest limits on small craft and fixed infrastructure ambiguity.
Sentinel-1 (ESA)ICEYECapella Space
Snow looks white. So does cloud. Physics tells them apart.Sentinel-2 snow cover extent and albedo mapping
Sentinel-2's shortwave infrared bands separate snow from cloud where visible light cannot, enabling 10–20 m snow-cover maps and surface albedo estimates critical for hydrology, climate and resort operations.
Sentinel-2 MSI (MultiSpectral Instrument)MODIS (Terra and Aqua)VIIRS I-band (Suomi NPP and NOAA-20)
Concrete cools slowly. Satellites can prove exactly how slowly.Thermal infrared urban heat island quantification
Thermal infrared sensors retrieve land surface temperature across entire cities in a single pass, resolving the heat penalty paid by dense impervious surfaces versus parks and water bodies. The physics is well understood; the constraints are resolution, revisit and cloud.
Landsat 8/9 TIRSECOSTRESS (ISS)ASTER (Terra, heritage)
Ice lies. C-band backscatter tells you which kind.SAR sea ice type classification and drift tracking
Synthetic aperture radar separates first-year ice, multi-year ice and open water by exploiting differences in volume scattering and surface texture, then tracks floe drift through repeat-pass image correlation. Summer melt complicates every classification scheme; knowing why matters as much as knowing the method.
Sentinel-1 EW (Extra-Wide Swath) modeICEYE SAR constellationRADARSAT-2 (heritage, still operational)
GPS signals were never meant to hit the ground. That accident is useful.GNSS reflectometry for soil moisture and sea surface roughness
GNSS-R exploits reflected navigation signals to infer surface dielectric properties and roughness. CYGNSS gives sub-daily tropical revisit that passive microwave cannot match at comparable scale, but a ~25 km resolution floor and vegetation ambiguity set real limits.
CYGNSS (NASA, 8-satellite constellation)Spire GNSS-R (commercial, 100+ satellite constellation)TechDemoSat-1 (UK, heritage)
Broadband sensors see water. Hyperspectral sensors see what is in it.Hyperspectral inland water constituent retrieval
Narrow-band hyperspectral imagery from PRISMA and EnMAP can separate chlorophyll-a, phycocyanin, coloured dissolved organic matter and suspended sediment in lakes and reservoirs where standard multispectral sensors produce ambiguous or meaningless results.
PRISMA (ASI)EnMAP (DLR/GFZ)DESIS (DLR on ISS)
Radar sees through cloud. It cannot see past five centimetres.SAR backscatter soil moisture retrieval
C-band SAR backscatter responds to soil dielectric constant, giving a quantitative proxy for near-surface volumetric water content. Sentinel-1's free, 12-day global repeat makes operational soil-moisture mapping feasible, with important caveats on depth and canopy.
Sentinel-1 (C-band, 5.405 GHz)ALOS-2 PALSAR-2 (L-band, 1.27 GHz)SAOCOM-1A/1B (L-band, 1.275 GHz)
The sea bottom is visible from orbit. Turbid water hides it completely.Satellite-derived bathymetry in shallow coastal waters
Multispectral satellites can estimate water depth in clear, optically shallow coastal zones by exploiting how blue and green light attenuate with depth. The method works to roughly 15–25 metres in clean water and fails entirely when turbidity or algae obscure the bottom.
Sentinel-2 MSILandsat 8/9 OLIPlanet SuperDove
Ice hides most of itself. Photons find the rest.ICESat-2 photon-counting lidar sea ice freeboard and thickness
ICESat-2's ATLAS instrument measures sea ice freeboard to centimetre precision using photon-counting lidar. Converting that height to thickness requires assumptions about snow load and ice density that remain the dominant source of error.
ICESat-2 ATLASCryoSat-2 SIRALSentinel-3 SRAL
Methane is invisible. TROPOMI makes the atmosphere confess.Sentinel-5P TROPOMI methane column mapping
TROPOMI's shortwave infrared channels map the total atmospheric methane column daily at 7-by-5.5 km resolution, flagging anomalies above oil and gas fields, landfills and wetlands. Large point sources are detectable; smaller facilities require commercial sensors to confirm.
Sentinel-5P TROPOMIGHGSatGOSAT-2
A single image lies. A year of images tells the truth.Commercial optical time-series crop type classification
Crop types diverge in their seasonal spectral trajectories far more than in any single snapshot. Dense time-series from Planet Dove and Sentinel-2, classified with machine-learning models trained on field labels, can map what is growing and where.
Planet Dove / SuperDoveSentinel-2 MSILandsat 8/9 OLI
Radar sees through leaves. Woody stems tell a different story.SAR L-band backscatter above-ground biomass estimation
L-band SAR backscatter correlates with above-ground biomass up to a saturation ceiling of roughly 100–150 t/ha, making it a practical but bounded tool for forest carbon accounting. Calibration against lidar or field inventory is not optional.
ALOS-2 PALSAR-2ESA BIOMASS (P-band, planned)Sentinel-1 (C-band)
Fires saturate the sensor. The physics still tells you how big they are.VIIRS and MODIS active fire detection and radiative power
VIIRS and MODIS mid-infrared channels detect active burning at continental scale, twice daily, and convert radiance excess into fire radiative power, a direct proxy for fuel consumption rate. Resolution floors and saturation set real limits that every operational user must understand.
VIIRS I-band (Suomi NPP, NOAA-20, NOAA-21)VIIRS M-band (Suomi NPP, NOAA-20, NOAA-21)MODIS (Terra and Aqua, heritage)
The ground sinks by millimetres. The physics records every one.InSAR permafrost thaw subsidence monitoring
Differential SAR interferometry detects millimetre-scale surface subsidence caused by permafrost active-layer thickening, using phase shifts between repeat passes. L-band systems maintain coherence where C-band fails, but separating frost heave from thaw settlement demands careful seasonal analysis.
ALOS-2 PALSAR-2NISAR (forthcoming, expected 2025)Sentinel-1 (C-band)
The ocean surface is a wind gauge. Radar reads it.Ocean surface wind speed and direction from SAR and scatterometry
C-band radar backscatter from centimetre-scale capillary waves encodes wind speed and direction across the ocean surface. Sentinel-1 resolves individual storm cells at sub-kilometre scale; MetOp ASCAT delivers daily global coverage at 12.5 km.
Sentinel-1 IW (Interferometric Wide Swath) modeMetOp ASCATCYGNSS (Cyclone Global Navigation Satellite System)
Coral looks nothing like sand. Fifteen metres of water can make them identical.Multispectral coral reef habitat classification
Multispectral satellites exploit spectral contrasts between coral, algae, seagrass and sand in the blue-green window to map reef habitats, but water-column attenuation and turbidity impose hard limits that no algorithm fully escapes.
WorldView-2 / WorldView-3 (Maxar)Sentinel-2 MSI (ESA / Copernicus)Planet SuperDove
Jammers announce themselves. Physics records the confession.Spaceborne RF spectrum monitoring and interference detection
Satellites carrying wideband software-defined radio receivers can detect, characterise and geolocate interference to GPS, satcom and radar bands from low Earth orbit. This page explains how TDOA/FDOA geolocation works, what accuracy is achievable, and where the method hits its limits.
Hawkeye 360 (HawkEye 360 Inc.)Kleos SpaceSpire Global (GNSS-R and RO payloads)
Cities grow at night and on weekends. Satellites notice.Sentinel-2 built-up area expansion and urban growth mapping
Sentinel-2's 10-metre multispectral bands resolve the spectral contrast between concrete, bare soil and vegetation well enough to classify built-up extent and quantify urban expansion rates from bi-temporal or time-series imagery. Cloud cover and construction-site ambiguity are real limits; SAR coherence fills both gaps.
Sentinel-2 MSI (ESA)Sentinel-1 C-band SAR (ESA)Landsat 8/9 OLI (USGS/NASA)
Lava saturates your sensor before you finish reading the pixel.Thermal infrared volcanic unrest and lava flow mapping
Volcanic heat overwhelms broad-band thermal sensors quickly, so effective monitoring stacks SWIR, mid-wave and thermal infrared data from ASTER, VIIRS, Sentinel-2 and ECOSTRESS to track effusion rates, dome growth and crater-lake unrest without saturation artefacts.
ASTER (Terra)VIIRS (NOAA-20 and Suomi-NPP)Sentinel-2 MSI (ESA)
Broadband pixels see colour. Spectrometers read chemistry.Hyperspectral mineral alteration and lithological mapping
Spaceborne imaging spectrometers resolve diagnostic absorption features that separate kaolinite from illite, jarosite from goethite, and barren rock from altered crust. Broadband multispectral sensors cannot do this reliably. Here is what current instruments can and cannot deliver.
EnMAP (DLR/GFZ, launched 2022)PRISMA (ASI, launched 2019)EMIT (NASA/JPL on ISS, deployed 2022)
Ice moves too fast for interferometry. Physics still leaves a trail.SAR offset tracking and InSAR glacier surface velocity
SAR interferometry and intensity offset tracking together measure glacier surface velocity across the full speed range, from millimetres per day on alpine glaciers to tens of metres per day on Greenland outlet glaciers, feeding directly into mass-balance and sea-level budgets.
Sentinel-1 A/B/C (C-band, 5.6 cm)ICEYE X-series (C-band)Capella Space (X-band, 3.1 cm)
Signals bent by free electrons reveal what no radar can see from below.GNSS radio occultation ionospheric electron density profiling
As a GNSS signal grazes the ionosphere during a limb occultation, its excess phase delay encodes vertical electron density structure. Abel inversion turns that delay into profiles of the F-layer, sporadic-E patches and total electron content, with honest caveats about where spherical symmetry fails.
COSMIC-2 / FORMOSAT-7Spire Global LEMUR-2PlanetiQ GNOMES
Mangroves sit between land and sea. Satellites read both at once.Multispectral mangrove extent and canopy density change detection
Mangrove forests are mapped and monitored using red-edge, NIR and SWIR spectral bands, SAR backscatter, and tidal-phase-controlled image selection. Accurate extent and canopy density change detection requires understanding where these methods break down.
Sentinel-2 MSILandsat 8/9 OLISentinel-1 SAR (C-band)
Oil kills Bragg waves. That silence is visible from orbit.SAR backscatter oil spill and marine slick detection
Synthetic aperture radar detects surface oil by the dampening effect it has on centimetre-scale sea roughness, producing dark patches in C- and X-band imagery. The method works within a narrow wind-speed window and cannot, on its own, distinguish mineral oil from fish-school slicks or rain cells.
Sentinel-1 IW / EW modes (C-band, 5.405 GHz)RADARSAT-2 (C-band)ICEYE constellation (X-band, ~9.65 GHz)
The atmosphere scatters light in ways a surface never can.Satellite aerosol optical depth retrieval and particulate mapping
Satellite sensors retrieve aerosol optical depth by separating aerosol signal from surface reflectance across multiple wavelengths and angles. The method is powerful and globally consistent, but column measurements alone cannot tell you where in the atmosphere the aerosol sits.
MODIS (Terra and Aqua)VIIRS (NOAA-20 and Suomi-NPP)MISR (Terra)
AIS goes dark at berth. The video does not.Video-from-space vessel dwell time and port throughput measurement
Sub-minute electro-optical video clips from LEO can time vessel arrivals, departures and berth occupancy at ports where AIS is unreliable or suppressed, building statistical throughput models that single frames cannot.
Planet SkySat videoSatellogic EarthView videoBlackSky Global
Ice moves in centimetres. The physics of photons catches it.Spaceborne lidar ice sheet and terrain elevation change detection
Repeat-track spaceborne lidar measures surface elevation change over ice sheets, glaciers and bare terrain by differencing profiles separated in time, revealing mass gain or loss without SAR phase ambiguity. Honest limits apply: cross-track separation, slope geometry and waveform saturation over fresh snow all require careful correction.
ICESat-2 ATLAS (NASA, 2018–present)GEDI (NASA/ISS, 2019–present)CryoSat-2 SIRAL (ESA, 2010–present)
Volcanoes cannot hide their breath. Neither can smelters.Sentinel-5P TROPOMI sulphur dioxide column mapping for volcanic and industrial emissions
TROPOMI maps sulphur dioxide columns globally every day at 3.5 km resolution, distinguishing stratospheric eruption plumes from the faint boundary-layer signal of industrial point sources, with a detection floor near 0.5 Dobson units.
Sentinel-5P TROPOMIAura OMIGEMS (GEO-KOMPSAT-2B)