- Optical Satellites: Instruments like MODIS and OLI capture visible
and infrared imagery.
- Radar Satellites: Synthetic aperture radar (SAR) satellites, such as
Sentinel-1, provide data regardless of weather conditions.
- Hyperspectral Satellites: These satellites, such as EnMAP, provide
rich spectral datasets for precise analysis of land and water.
- Environmental Monitoring: Satellites like Aqua and SMAP monitor
water cycles and soil moisture.
- Disaster Response: Satellites like RADARSAT support rapid response
during floods, earthquakes, and hurricanes.
- Climate Research: Missions such as GRACE-FO track changes in Earth’s
gravity field to study ice mass loss and sea-level rise.
- Definition: LEO satellites orbit between 160 km and 2,000 km
altitude.
- Examples: Landsat, Sentinel, and MODIS satellites operate in LEO,
providing high-resolution, frequent observations.
- Definition: GEO satellites remain fixed relative to the Earth’s
surface at an altitude of 35,786 km.
- Examples: Meteosat and GOES satellites are in GEO, offering constant
coverage of specific regions.
- Definition: MEO satellites orbit at altitudes between 2,000 km and
35,786 km.
- Examples: The Galileo constellation operates in MEO, primarily for
navigation but with Earth observation capabilities.
Constellations like the Sentinel series and PlanetScope revolutionize Earth observation by minimizing revisit times and enhancing global coverage. These systems integrate data across satellites for seamless observation.
Companies such as Planet Labs and Maxar Technologies deploy constellations for high-frequency monitoring of urban and natural environments.
Emerging constellations, like Starlink for IoT-based remote sensing, aim to integrate Earth observation with global internet services.
NASA has been a global leader in satellite remote sensing since its founding in 1958. It focuses on understanding the Earth system through a diverse range of satellite missions. The Landsat program, started in 1972 in partnership with the USGS, is one of the longest-running initiatives for Earth observation.
Notable missions include:
- Terra: Launched in 1999, Terra carries instruments like MODIS, CERES,
and ASTER to study land, atmosphere, and ocean interactions.
- Aqua: Focused on water-related processes, Aqua collects critical
climate and environmental data.
- Suomi NPP: Provides high-resolution imagery for weather forecasting
and climate research.
The Landsat program, jointly managed by NASA and the US Geological Survey (USGS), is the longest-running Earth observation initiative. Since its inception in 1972, the program has been instrumental in monitoring land-use changes, environmental processes, and climate dynamics. Key aspects of the Landsat series include:
Each generation of Landsat satellites has introduced significant
technological improvements:
- Landsat 1-3: Equipped with the Return Beam Vidicon (RBV) and
Multispectral Scanner System (MSS), these satellites pioneered
multispectral remote sensing.
- Landsat 4-5: Introduced the Thematic Mapper (TM), which provided
higher resolution and additional spectral bands.
- Landsat 7: Featured the Enhanced Thematic Mapper Plus (ETM+), enabling
panchromatic imaging and enhanced radiometric sensitivity.
- Landsat 8: Operational since 2013, it carries the Operational Land
Imager (OLI) and the Thermal Infrared Sensor (TIRS), providing improved
spectral coverage and reduced stray light contamination.
- Landsat 9: Launched in 2021, Landsat 9 continues the program’s legacy
with upgraded OLI and TIRS systems.
Landsat has made significant contributions across multiple
domains:
- Deforestation Monitoring: Landsat data has revealed deforestation
trends in the Amazon rainforest, guiding conservation policies.
- Urban Growth Analysis: Time-series datasets have enabled researchers
to map urban sprawl, such as the rapid growth of cities like Lagos and
Dubai.
- Agricultural Applications: Landsat supports crop monitoring,
irrigation management, and yield estimation, fostering food
security.
- Water Resource Management: Data has been used to monitor shrinking
glaciers, assess reservoir health, and predict water shortages.
- Climate Change Research: The series provides long-term datasets
essential for understanding phenomena such as sea-level rise,
desertification, and global vegetation changes.
The open-data policy adopted in 2008 has democratized access to Landsat imagery. Platforms like the USGS EarthExplorer and Google Earth Engine make decades of data freely available, enabling global-scale research and analysis.
The Landsat Next program is poised to advance the series with improved spatial, temporal, and spectral resolution, addressing emerging scientific and operational needs.
NASA’s Earthdata platform provides free and open access to datasets. Tools like Giovanni and Google Earth Engine integrate NASA data for analysis, fostering global scientific collaboration.
The European Space Agency (ESA), in collaboration with the European Union, spearheads the Copernicus program, the world’s largest Earth observation initiative. Its Sentinel series forms the backbone of this program, delivering high-resolution data for environmental monitoring, disaster management, and climate research. These satellites have been designed with modularity and continuity to ensure long-term data availability.
The Sentinel satellite series encompasses multiple missions tailored to specific observational needs, with a focus on advancing environmental monitoring. Notable missions include:
Sentinel-1, launched in 2014, consists of two satellites (Sentinel-1A
and Sentinel-1B) equipped with Synthetic Aperture Radar (SAR). These
instruments enable all-weather, day-and-night imaging
capabilities.
- Applications: Sentinel-1 provides high-resolution radar data for
monitoring land deformation, mapping floods, tracking sea-ice drift, and
assessing deforestation.
- Technological Highlights: SAR can penetrate clouds and rain, making
Sentinel-1 indispensable for areas with persistent cloud cover. Its
revisit time is optimized for rapid disaster response.
- Scientific Contributions: Sentinel-1 has been critical in mapping
earthquake-induced land shifts, such as during the 2015 Nepal
earthquake.
Sentinel-2, launched in 2015, is a pair of satellites (Sentinel-2A
and Sentinel-2B) equipped with multispectral imagers covering 13
spectral bands.
- Applications: The high-resolution imagery supports agriculture (crop
health monitoring), forestry (canopy cover assessments), and urban
mapping.
- Technological Highlights: The satellites have a wide swath width of
290 km and a revisit time of five days at the equator, ensuring frequent
and extensive data coverage.
- Scientific Contributions: Sentinel-2 has been widely used for
vegetation mapping and land cover classification, significantly
improving global land-use studies.
Sentinel-3, launched in 2016, is designed for marine and terrestrial
monitoring. Its Ocean and Land Colour Instrument (OLCI) is a key
feature, optimized for observing ocean color, vegetation health, and
atmospheric conditions.
- Applications: Sentinel-3 provides data on ocean productivity, coastal
zone dynamics, and land surface temperatures.
- Technological Highlights: OLCI features 21 spectral bands with high
radiometric accuracy, making it ideal for tracking algae blooms,
sediment plumes, and vegetation indices.
- Scientific Contributions: Sentinel-3 has been crucial in understanding
marine ecosystems, monitoring harmful algal blooms, and assessing
drought conditions.
Sentinel-5P, launched in 2017, is dedicated to monitoring atmospheric
composition. It carries the TROPOspheric Monitoring Instrument
(TROPOMI).
- Applications: Tracks air pollutants like nitrogen dioxide (\(NO_{2}\)), sulfur dioxide (\(SO_{2}\)), and methane (\(CH_{4}\)).
- Technological Highlights: TROPOMI provides daily global coverage with
a spatial resolution of 7 km x 3.5 km, enabling detailed air quality
assessments.
- Scientific Contributions: Sentinel-5P has been instrumental in
visualizing global \(NO_{2}\)
reductions during the COVID-19 lockdowns and detecting methane
leaks.
ESA’s Sentinel missions work in conjunction with other space agencies, such as NASA and JAXA, to form a comprehensive Earth observation network. Programs like CryoSat and Biomass extend ESA’s capabilities into polar monitoring and global forest biomass estimation.
Data from the Copernicus program is freely accessible through platforms like the Copernicus Open Access Hub. The Sentinel satellites ensure consistent data quality and open availability, fostering innovation in fields like agriculture, climate research, and disaster management.
Future iterations of the Sentinel series aim to integrate advanced sensors, such as hyperspectral imaging instruments, and leverage AI for near-real-time data analysis. These advancements will address evolving environmental and societal challenges.
The European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) is an intergovernmental organization established in 1986. Its primary mission is to deliver accurate and reliable satellite data to support weather forecasting, climate monitoring, and environmental management. Headquartered in Darmstadt, Germany, EUMETSAT operates a fleet of meteorological and oceanographic satellites, ensuring continuity of data critical for European and global meteorological services.
EUMETSAT operates two main satellite series, the Meteosat and MetOp programs, alongside a growing role in the Copernicus program. These satellites provide real-time and long-term datasets essential for weather prediction and climate science.
The Meteosat series consists of geostationary satellites that monitor
weather conditions over Europe, Africa, and the Atlantic Ocean.
- Generations of Meteosat:
- First Generation (1977–2007): Early satellites focused on visual and
infrared imaging for basic weather forecasting.
- Second Generation (Meteosat-8 to Meteosat-11): Introduced in 2002,
these satellites offer enhanced capabilities, such as rapid scanning and
better temporal resolution.
- Third Generation (Meteosat Third Generation, MTG): The latest
generation, with its first satellite launched in 2022, includes the
Flexible Combined Imager (FCI) and Lightning Imager (LI) for improved
weather monitoring and thunderstorm detection.
- Applications: Meteosat data supports short-term weather forecasts,
storm tracking, and nowcasting. It has been pivotal in tracking severe
weather events like hurricanes and floods.
The MetOp program is EUMETSAT’s series of polar-orbiting satellites,
developed in collaboration with ESA.
- Generations of MetOp:
- MetOp-A, B, and C: Operated from 2006 to the present, these satellites
carry advanced instruments like the Advanced Microwave Sounding Unit
(AMSU) and the Global Navigation Satellite System Receiver for
Atmospheric Sounding (GRAS).
- MetOp Second Generation (MetOp-SG): Scheduled for launches from 2024,
this series will include enhanced sensors for atmospheric composition,
temperature, and humidity profiling.
- Applications: MetOp satellites are crucial for medium- and long-term
weather forecasting. They contribute to Numerical Weather Prediction
(NWP) models and monitor climate variables like sea surface temperatures
and atmospheric ozone levels.
EUMETSAT is a key partner in the Copernicus program, managing data
streams from ocean and atmospheric missions. It operates Sentinel-3,
Sentinel-4, and Sentinel-5.
- Sentinel-3: Focused on marine and terrestrial monitoring, including
ocean temperature and land surface analysis.
- Sentinel-4 and Sentinel-5: Geostationary and polar-orbiting satellites
dedicated to atmospheric composition and air quality.
EUMETSAT’s satellites support a wide range of applications:
- Weather Forecasting: EUMETSAT data underpins meteorological services
worldwide, providing critical information for storm warnings, cyclone
tracking, and aviation safety.
- Climate Monitoring: Long-term datasets from Meteosat and MetOp
satellites enable trend analyses of global temperatures, ocean heat
content, and greenhouse gases.
- Oceanography: Sentinel-3, operated by EUMETSAT, monitors sea surface
temperature, sea-level rise, and marine ecosystems.
- Disaster Management: EUMETSAT data supports emergency responses to
floods, droughts, and wildfires, enhancing global resilience to natural
disasters.
EUMETSAT provides open access to its data through platforms like EUMETCast and WEkEO. It collaborates with international organizations such as NOAA, JMA, and ECMWF, ensuring interoperability and data sharing. The Global Space-based Inter-Calibration System (GSICS) is an example of EUMETSAT’s leadership in maintaining high-quality satellite observations.
EUMETSAT is committed to advancing its capabilities to address emerging challenges. The MTG and MetOp-SG programs will enhance data resolution and revisit times, supporting high-accuracy weather models and climate projections. Additionally, integrating artificial intelligence and machine learning into data processing pipelines is a focus area to improve prediction accuracy.
| Provider | Satellite Name | Revisit Time | Spatial Resolution | Spectral Resolution | Radiometric Res. (bits) | Operation Years |
|---|---|---|---|---|---|---|
| NASA | Landsat 8 | 16 days | 15 m, 30 m | 11 bands | 12 | 2013–Present |
| NASA | Landsat 9 | 16 days | 15 m, 30 m | 11 bands | 12 | 2021–Present |
| NASA | Aqua | Daily | 1 km, 10 km | 36 bands | 12 | 2002–Present |
| NASA | Terra | Daily | 1 km, 250 m | 36 bands | 12 | 1999–Present |
| NASA | SRTM | Single mission | 30 m, 90 m | Radar interferometry | 16 | 2000 |
| NASA | ICESat (GLAS) | 183 days, 91 days | 70 m, 17 m | Laser altimetry | 12 | 2003–2010, 2018–Present |
| NASA | GRACE | Monthly | 200 km, 300 km | Accelerometer data | N/A | 2002–2017 |
| NASA | GRACE-FO | Monthly | 200 km, 300 km | Accelerometer data | N/A | 2018–Present |
| ESA | Sentinel-1 | 6 days | 5 m, 40 m | SAR imaging | 16 | 2014–Present |
| ESA | Sentinel-2 | 5 days | 10 m, 60 m | 13 bands | 12 | 2015–Present |
| ESA | Sentinel-3 (OLCI) | 2 days | 300 m | 21 bands | 12 | 2016–Present |
| ESA | Sentinel-5P | 1 day | 7 km, 3.5 km | Air pollutants | 12 | 2017–Present |
| EUMETSAT | Meteosat Third Gen. | 10 min | 1 km | Visible, IR, LI | 16 | 2022–Present |
| EUMETSAT | MetOp-A/B/C | 12 hours | 10 km, 50 km | Multiple bands | 12 | 2006–Present |
The following are important links regarding main providers and
respective satellites.
NASA: NASA
Landsat 8: Landsat
8
Landsat 9: Landsat
9
Aqua: Aqua
Terra: Terra
SRTM: SRTM
ICESat (GLAS): ICESat
GRACE: GRACE
GRACE-FO: GRACE-FO
ESA: ESA
Sentinel-1: Sentinel-1
Sentinel-2: Sentinel-2
Sentinel-3 (OLCI): Sentinel-3
Sentinel-5P: Sentinel-5P
EUMETSAT: EUMETSAT
Meteosat Third Gen: Meteosat Third
Gen
MetOp-A/B/C: MetOp
