- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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-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 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-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-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 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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.
- 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 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.