Operational Earth-Sensing Satellites in Earth Orbit

Status snapshot: 20 January 2026 (America/Denver). Prepared in an IEEE-style technical report format.

Document type: Technical overview and reference guide Scope: Major operational civil and commercial Earth-observing missions and constellations

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Abstract

This report summarizes major operational Earth-sensing satellites currently in Earth orbit and describes, in engineering terms, the principal sensors they carry and the applications they enable. “Earth sensing” is used broadly to include land imaging, meteorology, oceanography, cryosphere monitoring, atmospheric composition, hydrology, and gravity/geodesy. The spaceborne sensor modalities covered include passive optical multispectral and hyperspectral imagers; thermal infrared radiometers; passive microwave radiometers and sounders; synthetic aperture radar (SAR); radar and interferometric radar altimeters; GNSS reflectometry; lidar/laser altimetry; and ultraviolet/visible/infrared spectrometers for trace gases.

Index Terms

Earth observation, remote sensing, multispectral imaging, hyperspectral imaging, thermal infrared, passive microwave, SAR, interferometric SAR, radar altimetry, GNSS-R, lidar, atmospheric composition, meteorological satellites, Copernicus, Landsat, JPSS, GOES.

Contents

  1. I. Scope, Definitions, and “Operational” Criteria
  2. II. Sensor Modalities: What They Measure and Why They Matter
  3. III. Major Operational Civil Missions and Constellations
  4. IV. Commercial and Public-Private Earth-Observation Constellations
  5. V. Cross-Cutting Applications and Typical Products
  6. VI. Data Access, Processing, and Standards
  7. VII. Additional Reading
  8. References
  9. Appendix A: Selected Quick-Reference Mission Table

I. Scope, Definitions, and “Operational” Criteria

The global Earth-observation ecosystem contains hundreds of active spacecraft. To keep this document usable and print-friendly, this report focuses on widely-used operational missions that provide systematic acquisition (global or near-global) or uniquely important measurements (e.g., radar altimetry, greenhouse gases, gravity). For large commercial constellations, the report describes representative sensor families rather than enumerating every spacecraft.

Operational is used in the pragmatic engineering sense: a platform is acquiring data on a routine basis and delivering products to users. Some platforms are in commissioning (early operations) or late-life (degraded capability); these are identified explicitly.

For exhaustive, filterable lists of operational satellites and instruments (including status, measurement types, and agencies), consult OSCAR/Space and the CEOS Missions-Instruments-Measurements catalogues [1], [2].

II. Sensor Modalities: What They Measure and Why They Matter

A. Passive Optical Multispectral Imaging (VIS/NIR/SWIR)

Multispectral imagers measure reflected solar radiance in a limited set of discrete spectral bands (typically 4–13 bands spanning visible, near-infrared, and shortwave infrared). These data support quantitative retrievals such as surface reflectance, vegetation indices (NDVI/EVI), burn severity (NBR), water indices (NDWI), and mineral/soil indicators. Key engineering attributes are spectral band placement, radiometric calibration, spatial resolution, swath width, signal-to-noise ratio, and revisit frequency.

Representative systems include Landsat OLI/OLI-2 and Sentinel-2 MSI. Landsat OLI provides 30 m multispectral and 15 m panchromatic imagery over a 185 km swath and includes coastal aerosol and cirrus bands [6]. Sentinel-2 MSI samples 13 bands with 10 m, 20 m, and 60 m products for land and coastal applications [9].

B. Hyperspectral Imaging (Imaging Spectroscopy)

Hyperspectral imagers measure contiguous or narrowly spaced spectral samples (hundreds of bands) typically across VIS–SWIR. This enables improved discrimination of materials and biophysical traits (e.g., leaf pigments, water content, mineralogy) and supports physics-based inversion using radiative transfer models. Compared to multispectral systems, hyperspectral missions generally trade swath width and/or revisit for spectral richness.

EnMAP is a dedicated hyperspectral mission covering approximately 420–2450 nm with 30 m pixels and a ~30 km swath [58], [59]. PACE carries the OCI ocean color instrument optimized for aquatic and atmospheric optical properties [40].

C. Thermal Infrared Radiometry (TIR)

Thermal infrared sensors measure emitted radiance, enabling land/sea surface temperature (LST/SST), evapotranspiration estimation, urban heat island mapping, and wildfire characterization. Engineering considerations include band placement near 10–12 µm, calibration stability, atmospheric correction, and (for fire) dynamic range and saturation performance.

Landsat TIRS/TIRS-2 provides two thermal bands used to retrieve land surface temperature [6], [12]. Sentinel-3 SLSTR provides multi-band VIS–TIR radiometry and includes TIR channels optimized for active fire detection and fire radiative power [54], [55].

D. Passive Microwave Radiometry and Sounding

Passive microwave radiometers measure natural microwave emission, which is sensitive to soil moisture, ocean salinity, precipitation, sea ice concentration, and atmospheric water vapor and temperature. Microwave instruments can observe through most clouds and offer day/night coverage, making them indispensable for weather and climate.

SMAP uses an L-band radiometer to retrieve global soil moisture and freeze/thaw state [44]. ESA’s SMOS uses L-band interferometric radiometry (MIRAS) to retrieve soil moisture and ocean salinity [45]. JAXA’s AMSR2 provides multi-frequency microwave radiometry for precipitation, SST, sea ice, and water vapor retrievals [46]. Operational meteorological sounders on polar platforms (e.g., CrIS, ATMS, IASI) drive numerical weather prediction skill.

E. Synthetic Aperture Radar (SAR)

SAR actively illuminates the Earth with microwave pulses and synthesizes a large antenna aperture via platform motion. SAR enables high-resolution imaging independent of daylight and with strong cloud-penetrating capability. Measurement diversity comes from wavelength (X/C/L-band), polarization (single/dual/quad-pol), incidence angle, and imaging modes.

SAR’s coherent phase enables interferometry (InSAR) for ground deformation and topography, coherence-based change detection, and polarimetry for vegetation/ice/soil characterization. C-band SAR (Sentinel-1, RADARSAT) is widely used for floods, sea ice, and maritime monitoring, while L-band SAR (ALOS-2, NISAR L-band) improves penetration through vegetation and is valuable for biomass and subsidence.

F. Radar Altimetry and Wide-Swath Surface Water Topography

Radar altimeters measure range to the surface, enabling sea surface height (SSH), significant wave height, and wind speed retrievals. Conventional nadir altimeters provide along-track profiles; modern SAR-mode and interferometric techniques improve precision and enable higher-resolution measurements of coastal and inland waters.

Sentinel-6 Michael Freilich continues the long-term sea-level record [24]. SWOT’s KaRIn interferometric altimeter provides wide-swath measurements of ocean and inland water surface topography [41], [42].

G. Lidar and Laser Altimetry

Lidar/laser altimetry measures the time-of-flight of laser pulses to derive precise elevation, vertical structure, and (for certain wavelengths) aerosol/cloud optical properties. ICESat-2’s photon-counting ATLAS enables ice sheet elevation change and sea ice freeboard estimation [47]. GEDI’s waveform lidar on the ISS measures forest canopy height and vertical structure, supporting biomass estimation [52].

H. Atmospheric Composition Spectrometry and UV/VIS/NIR Sounding

Spectrometers and sounders retrieve trace gases, aerosols, and vertical profiles. Sentinel-5P’s TROPOMI provides daily global mapping of key pollutants and greenhouse-gas proxies at high spatial resolution relative to earlier UV/VIS instruments [22], [60]. GOSAT-2 provides targeted greenhouse gas retrievals (CO2, CH4) using FTS-based spectroscopy [61].

I. GNSS Reflectometry (GNSS-R)

GNSS-R uses reflections of GNSS signals from the Earth’s surface to infer ocean surface roughness (winds) and, in some cases, land surface properties. CYGNSS uses GNSS-R for tropical cyclone and ocean wind observations [53].

III. Major Operational Civil Missions and Constellations

A. Land Imaging and Land Surface Change

1) Landsat 8 and Landsat 9 (NASA/USGS)

  • Orbit/coverage: Sun-synchronous LEO; 16-day repeat per satellite; paired 8-day offset between Landsat 8 and 9 for higher effective revisit.
  • Sensors: OLI/OLI-2 (VIS/NIR/SWIR multispectral + 15 m panchromatic) and TIRS/TIRS-2 (two TIR bands for LST).
  • Key engineering details:
    • OLI includes coastal aerosol and cirrus bands and provides 30 m multispectral and 15 m panchromatic imagery over a 185 km swath [6].
    • TIRS measures emitted thermal radiance in two bands used for surface temperature retrieval; TIRS-2 improves performance and stray-light behavior while remaining closely aligned to Landsat 8 heritage [12].
  • Primary products and uses:
    • Surface reflectance and surface temperature analysis-ready products used for agriculture, forestry, water management, urban growth, and land-cover change detection [7].
    • Fire impacts (burn severity), drought/irrigation mapping (via vegetation indices and thermal-driven ET models), glacier and snow mapping, coastal turbidity and water quality (with careful atmospheric correction).

2) Copernicus Sentinel-2A/2B (ESA/EU)

  • Sensor: Multi-Spectral Instrument (MSI) with 13 bands; 10 m/20 m/60 m spatial resolutions designed for land and coastal monitoring [9].
  • Strengths: High spatial resolution for vegetation and built environment; band set includes red-edge for vegetation condition and SWIR for moisture/mineral sensitivity.
  • Typical uses: Crop type/phenology, forest disturbance, habitat mapping, flood extent (with cloud limitations), shoreline change, snow cover and albedo estimation, and disaster mapping workflows in emergency response.

B. Weather and Environmental Monitoring

1) NOAA JPSS Polar Orbiters: Suomi NPP, NOAA-20, NOAA-21

  • Role: Operational polar meteorology and global environmental monitoring.
  • Core sensor suite: VIIRS (imaging radiometer), CrIS (IR sounder), ATMS (microwave sounder), OMPS (ozone mapper/profiler). Mission descriptions and instrument sets are provided by NOAA [14], [15].
  • VIIRS details: Multispectral radiometer with moderate-resolution bands plus 375 m “I-band” fire capability and a Day/Night Band (DNB) for low-light imaging [56], [57].
  • Typical operational uses: Numerical weather prediction (radiance assimilation), cloud properties, SST, sea ice, aerosol optical depth, snow cover, night lights, and global active fire/thermal anomaly products [56].

2) GOES-R Series (NOAA): GOES-16 (East) and GOES-18 (West)

  • Orbit: Geostationary; continuous hemispheric coverage enables rapid refresh for nowcasting and severe weather monitoring.
  • Key sensors:
    • ABI (Advanced Baseline Imager): 16-band imager; flexible scan modes enabling full-disk, regional, and mesoscale rapid refresh with spatial resolution approximately 0.5–2 km depending on band [26], [27].
    • GLM (Geostationary Lightning Mapper): Near-infrared optical transient detector mapping total lightning over the Americas with near-uniform ~10 km resolution, supporting severe storm warning operations [28], [29].
  • Uses: Convective initiation and storm evolution, wildfire detection and smoke tracking, marine fog/low cloud monitoring, atmospheric motion vectors, volcanic ash detection, and lightning-based storm intensification indicators.

3) EUMETSAT Polar and GEO Systems (Europe): Metop (polar) and Meteosat/MTG (geostationary)

  • Metop-B/Metop-C (polar): Operational meteorological missions carrying IR and microwave sounding and atmospheric composition instruments (e.g., IASI, ASCAT, GOME-2, GRAS), supporting NWP and climate reanalysis [30], [31].
  • Meteosat Second Generation (MSG): SEVIRI provides rapid-refresh imagery for Europe/Africa weather monitoring; operational context and spacecraft status are maintained by EUMETSAT [18], [32].
  • Meteosat Third Generation (MTG): MTG-I1 introduces the Flexible Combined Imager (FCI) and Lightning Imager (LI) for improved spectral/temporal performance and lightning mapping in the European GEO sector [33].

4) Japan Meteorological Agency: Himawari-8/Himawari-9

  • Sensor: AHI (Advanced Himawari Imager), a 16-band geostationary imager enabling high-frequency monitoring of clouds, aerosols, fires, and ocean/land surface features in the Asia–Pacific region [34], [35].
  • Uses: Tropical cyclone monitoring, convection tracking, volcanic ash and wildfire smoke, and regional environmental products analogous to ABI workflows.

5) China Meteorological Administration: Fengyun-4 Series (selected)

  • Sensor suite (FY-4A example): Includes the AGRI advanced imager and infrared sounding capability (GIIRS), supporting weather monitoring and atmospheric profiling [36].
  • Uses: Regional GEO weather surveillance and environmental monitoring across East Asia and adjacent oceans.

C. Ocean, Cryosphere, and Surface Water Topography

1) Copernicus Sentinel-3A/3B

  • Sensors: OLCI (ocean/land color radiometry), SLSTR (surface temperature), SRAL (radar altimeter), plus microwave radiometry and precise orbit determination elements [20], [55].
  • Core uses: Ocean color (chlorophyll and water constituents), SST, sea ice edge and temperature, land surface temperature, and sea surface height/waves in support of ocean forecasting and climate services.

2) Sentinel-6 Michael Freilich (Sentinel-6A) and Sentinel-6B (commissioning/early operations)

  • Role: Reference-class sea surface height measurement for climate-quality sea-level rise monitoring.
  • Sentinel-6A: Operational sea surface topography mission continuing the long-term record [24].
  • Sentinel-6B: Launched in November 2025; status in early 2026 is commissioning/early operations per WMO OSCAR and NASA mission updates [38], [39].
  • Use cases: Global and regional sea-level trends, marine heat wave context (with SST), ocean circulation constraints, and improved coastal/inland performance from modern altimetry processing chains.

3) SWOT (Surface Water and Ocean Topography)

  • Primary instrument: KaRIn (Ka-band Radar Interferometer) plus a conventional nadir altimeter, enabling wide-swath surface water mapping [41], [42].
  • Uses: Mesoscale and submesoscale ocean topography, river slope/discharge proxies, lake/reservoir storage change, floodplain dynamics, and hydrologic model evaluation.

4) CryoSat-2 and ICESat-2

  • CryoSat-2: Radar altimetry (SIRAL) optimized for ice sheets and sea ice thickness retrievals [43].
  • ICESat-2: Photon-counting laser altimeter (ATLAS) for ice elevation change, sea ice freeboard, and inland water/vegetation structure proxies [47].
  • Uses: Ice-sheet mass balance attribution, sea ice thickness/roughness, glacier elevation change, and sea-level contribution estimates (in combination with gravimetry and models).

D. Atmospheric Composition, Air Quality, and Greenhouse Gases

1) Sentinel-5P (TROPOMI)

  • Sensor: TROPOMI UV/VIS/NIR/SWIR spectrometer providing daily global observations of atmospheric trace gases and aerosols [22], [60].
  • Uses: NO2/SO2/O3/CO monitoring, smoke and volcanic plume tracking, long-term air quality policy evaluation, and methane hotspot screening (with appropriate retrieval caveats).

2) Aura (NASA) and OMPS (NOAA JPSS)

  • Aura: Atmospheric chemistry observatory; instruments include OMI and MLS (mission status and operational notes are distributed through NASA and WMO databases) [51].
  • OMPS: Ozone mapping/profiling suite on JPSS satellites supporting operational ozone and UV products [14].

3) OCO-2 and OCO-3 (NASA)

  • Measurement: High-precision CO2 column retrievals and solar-induced fluorescence for carbon cycle science and ecosystem productivity indicators [49], [50].
  • OCO-3: ISS-mounted pointing capability supports target-mode mapping of emissions and urban/industrial regions.

4) GOSAT-2 (JAXA/partners)

  • Sensors: TANSO-FTS-2 and CAI-2 designed for greenhouse-gas retrievals and cloud/aerosol screening [61].
  • Uses: Carbon cycle constraints, emissions verification research, and long-term greenhouse-gas trend monitoring in combination with other missions.

E. Hydrology, Soil Moisture, and Precipitation

1) SMAP (NASA) and SMOS (ESA)

  • SMAP: L-band radiometry for surface soil moisture and freeze/thaw; supports drought monitoring, agricultural modeling, and flood/landslide susceptibility context [44].
  • SMOS: L-band interferometric radiometer (MIRAS) for soil moisture and ocean salinity; supports ocean circulation and hydrologic applications [45].

2) GPM Core Observatory (NASA/JAXA)

  • Sensors: Dual-frequency precipitation radar (DPR) and GPM Microwave Imager (GMI) providing precipitation structure and intensity measurements [48].
  • Uses: Global precipitation estimation (IMERG family via constellation), extreme rainfall characterization, hydrologic forecasting inputs, and climate precipitation variability.

F. Radar Imaging for All-Weather Land and Maritime Monitoring

1) Sentinel-1 (ESA/EU)

  • Sensor: C-band SAR supporting wide-area routine acquisition and rapid response imaging. Sentinel mission pages and data portals provide operational status and acquisition notes [19], [37].
  • Engineering strengths: Coherent phase stability supports InSAR deformation mapping (subsidence, earthquakes, volcanism) at millimeter-to-centimeter scales over time. Dual polarization modes support vegetation and sea ice classification.
  • Uses: Flood mapping (cloud independent), sea ice edge and drift, oil spill detection (context dependent), maritime surveillance (ship detection), landslide deformation monitoring, and infrastructure stability studies.

2) RADARSAT Constellation Mission (CSA)

  • Sensor: C-band SAR constellation designed for operational monitoring with frequent revisit and multiple imaging modes [16].
  • Uses: Maritime domain awareness (ice and ship monitoring), disaster response, agriculture, and land deformation workflows.

3) ALOS-2 (JAXA)

  • Sensor: PALSAR-2 L-band SAR enabling improved vegetation penetration and coherence for forest and deformation applications [17].
  • Uses: Forest structure and biomass proxy studies, landslide and subsidence monitoring, and disaster mapping in cloudy regions.

4) NISAR (NASA/ISRO)

  • Sensors: Dual-frequency SAR mission (L-band and S-band) with systematic global coverage plans; NASA mission overview provides sensor concept and application focus [56a].
  • Uses: Ecosystem change and biomass-relevant observables, ice dynamics, earthquakes and volcanism, land subsidence, and inundation mapping. Dual-frequency observations support improved separation of scattering mechanisms and vegetation/soil contributions.

G. Newer Biology/Ocean Optics Missions

1) PACE (NASA)

  • Sensors: Ocean Color Instrument (OCI) plus polarimeters (SPEXone and HARP2) for advanced aerosol/cloud and ocean color retrievals [40].
  • Uses: Phytoplankton functional type indicators, harmful algal bloom context, coastal water quality, aerosol characterization for improved atmospheric correction.

2) EarthCARE (ESA/JAXA)

  • Sensor suite: Combined active and passive sensors (lidar and cloud profiling radar with supporting imager/radiometer) designed to characterize clouds, aerosols, and radiative fluxes; ESA/JAXA documentation describes the mission’s product stream and science objectives [62], [63].
  • Uses: Cloud-aerosol interaction studies, improved radiative forcing estimates, and evaluation of model parameterizations.

3) EnMAP (Germany)

  • Sensor: Pushbroom hyperspectral imager covering ~420–2450 nm, 30 m GSD, ~30 km swath; mission specifications and overview documents describe sampling and revisit [58], [59].
  • Uses: Vegetation traits, mineral mapping, inland/coastal water constituents, and ecosystem condition indicators.

H. Gravity and Geodesy

GRACE-FO (NASA/GFZ)

  • Measurement concept: Satellite-to-satellite ranging and precise orbit determination enable time-variable gravity field estimation, revealing mass redistribution.
  • Uses: Groundwater depletion, ice sheet mass change, drought characterization, and large-scale hydrologic storage change. NASA mission overview describes the mission concept and continuity with GRACE [23].

I. Late-Life and Platform Notes

Some long-running platforms remain valuable but are near retirement or have evolving operations. Examples include EOS-era platforms such as Terra and Aqua (MODIS heritage) and composition missions like Aura. Users should consult current mission status pages and operations dashboards for any near-real-time constraints (e.g., planned instrument calibrations, downlink outages) [64], [65].

IV. Commercial and Public-Private Earth-Observation Constellations

Commercial providers increasingly deliver high-cadence and high-resolution imagery, radar, and specialized greenhouse-gas products. Data access and licensing vary substantially; many systems provide analytic-ready products but may restrict redistribution.

A. Optical Multispectral and High-Resolution Electro-Optical

1) PlanetScope (Planet “Dove/SuperDove” fleet)

  • Sensor family: Medium-resolution multispectral imaging; near-daily global land coverage is achieved via a large constellation [66].
  • Spectral coverage: Original Doves provide RGB+NIR; SuperDoves add coastal blue, yellow, red-edge, and “green I” bands for improved land and water analyses [66].
  • Uses: Time series change detection at field-to-city scales (agriculture, construction, mining), rapid event monitoring (floods, landslides), and baseline mapping for analytics pipelines.

2) SkySat (Planet)

  • Sensor family: High-resolution panchromatic + 4-band multispectral imagery; orthorectified products sampled at ~50 cm; agile tasking supports targeted collections [67].
  • Uses: Infrastructure monitoring, disaster damage assessment, vessel and port activity context, and video products for dynamic activity analysis (subject to policy and licensing constraints).

3) Maxar high-resolution missions (selected)

  • WorldView-3: High-resolution multispectral with additional SWIR capability and atmospheric characterization bands (CAVIS), used for mapping, disaster response, and material discrimination [68].
  • WorldView Legion: Next-generation fleet intended to expand high-resolution capacity and revisit; deployment and operationalization has been ongoing in the mid-2020s [69].

4) Airbus Pléiades Neo

  • Capability: Very-high-resolution optical imaging for mapping and intelligence-grade products; constellation concept provides increased revisit [70].

B. Commercial SAR Constellations

1) ICEYE

  • Capability: X-band SAR constellation delivering frequent revisit and operational flood/disaster mapping; constellation overview and capabilities are maintained by ICEYE [71].
  • Uses: Flood extent and depth proxies (with modeling), maritime surveillance, infrastructure change detection, and persistent monitoring in cloud-prone regions.

C. Commercial Greenhouse-Gas Monitoring

GHGSat (selected)

  • Capability: Targeted methane monitoring from space using high-resolution spectroscopy; product focus is point-source detection and quantification workflows [72].

Note: Commercial capabilities evolve rapidly. For current sensor lists, orbital deployments, and access mechanisms, consult provider technical documentation and CEOS/EO databases [2].

V. Cross-Cutting Applications and Typical Products

A. Disaster Response (Floods, Fires, Volcanoes, Earthquakes)

B. Agriculture and Food Security

C. Oceans and Coastal Zones

D. Climate and Long-Term Environmental Change

VI. Data Access, Processing, and Standards

A. Primary Data Portals (Selected)

B. Analysis-Ready Data and Interoperability

For operational exploitation, analysis-ready data (ARD) and consistent metadata are critical. Landsat Collection 2 and Sentinel processing chains emphasize radiometric calibration, geolocation accuracy, and quality flags. Many users access data through cloud-native catalogs and STAC-like metadata patterns. CEOS coordination efforts and the EO Handbook/CEOS databases provide cross-mission context for measurements, instruments, and standards [2], [3].

C. Operational Monitoring and “Reality Checks”

Operational use often depends on ground segment availability and downlink. As a concrete example, Copernicus has published short-notice data unavailability bulletins when relay assets or ground systems experience anomalies (e.g., Sentinel-1A/1C data outage on 14 Jan 2026) [37].

VII. Additional Reading

A. Books (Foundational)

B. Articles and Technical Documentation (Selected)

C. Reference Databases for Mission Discovery

References

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Note on references: Web resources are listed in IEEE online format with access date. Some URLs may redirect as agencies reorganize web properties.

Appendix A: Selected Quick-Reference Mission Table

This table is intentionally selective and focuses on high-impact operational missions and representative commercial constellations. For exhaustive mission inventories, use OSCAR/Space and CEOS databases [1], [2].

Domain Mission / Program (Selected) Primary Sensors Representative Uses
Land imaging Landsat 8/9; Sentinel-2A/2B OLI/OLI-2 + TIRS/TIRS-2; MSI Land cover change, agriculture, water resources, urban growth
Weather (polar) Suomi NPP; NOAA-20; NOAA-21 (JPSS) VIIRS, CrIS, ATMS, OMPS NWP, clouds, aerosols, SST/sea ice, global fires
Weather (GEO) GOES-16/18; MSG/MTG; Himawari-8/9; FY-4 ABI/GLM; SEVIRI/FCI/LI; AHI; AGRI/GIIRS Nowcasting, severe storms, fires/smoke, volcanic ash
Ocean & land color Sentinel-3; PACE OLCI; OCI (+ polarimeters) Ocean ecology, HAB context, coastal water quality, aerosols
Surface temperature Sentinel-3; Landsat; GOES SLSTR; TIRS; ABI IR bands SST/LST, heat stress, wildfire monitoring
SAR imaging Sentinel-1; RCM; ALOS-2; NISAR C-band SAR; C-band SAR; L-band SAR; L+S band SAR Floods, sea ice, InSAR deformation, vegetation structure
Altimetry Sentinel-6A/6B; SWOT; CryoSat-2 Nadir altimeters; KaRIn; ice-optimized radar altimeter Sea level, ocean circulation, rivers/lakes, ice thickness
Soil moisture SMAP; SMOS; AMSR2 L-band radiometry; L-band interferometric radiometry; multi-frequency radiometry Drought monitoring, hydrology, ocean salinity (SMOS)
Precipitation GPM Core DPR + GMI Global precipitation, extremes, hydrologic forcing
Composition Sentinel-5P; Aura; OCO-2/3; GOSAT-2 UV/VIS/NIR/SWIR spectrometers; microwave/UV chemistry suite; CO2 spectrometers; FTS Air quality, emissions research, carbon cycle
Gravity GRACE-FO Satellite-to-satellite ranging Groundwater, ice mass change, drought severity
Commercial optical PlanetScope; SkySat; Maxar; Pléiades Neo Multispectral + pan High-cadence monitoring, infrastructure, damage assessment
Commercial SAR ICEYE (selected) X-band SAR Persistent monitoring, flood/disaster response
Commercial GHG GHGSat (selected) High-resolution spectroscopy Methane point-source detection and quantification

End of report.