Earth Observation from Space — How Satellites Monitor Our Planet

Earth observation (EO) satellites provide a continuous, global view of our planet that is impossible to achieve from the ground. They measure everything from sea surface temperature and ice sheet thickness to crop health, air pollution, and the expansion of cities. The data they generate underpins weather forecasting, climate science, disaster response, agriculture, insurance, urban planning, and national security.

The modern EO ecosystem combines government flagship missions (Landsat, Copernicus/Sentinel, GOES) with rapidly growing commercial constellations (Planet Labs, Maxar, BlackSky). Planet Labs alone images the entire Earth's landmass every day at 3-metre resolution using a fleet of over 200 small satellites. Together, these systems generate petabytes of data daily.

Earth observation is one of the most tangible ways that space technology directly benefits life on the ground. When a wildfire breaks out, satellite thermal imaging detects it within minutes. When a flood threatens a region, synthetic aperture radar (SAR) maps the extent of inundation through cloud cover. When climate negotiators need evidence, decades of satellite records provide it.

Climate Monitoring: Satellites have provided continuous climate data since the 1970s. They measure global temperature, sea level rise (3.4 mm/year), ice sheet mass loss, atmospheric CO₂ concentrations, and ocean heat content. This long-term record is essential for understanding and projecting climate change.

Disaster Response: The International Charter on Space and Major Disasters, activated over 800 times since 2000, provides free satellite imagery to disaster-affected countries within hours. SAR satellites like Sentinel-1 can image through clouds and at night, critical for flood and earthquake response.

Agriculture: Satellite-derived vegetation indices (NDVI), soil moisture data, and weather monitoring drive precision agriculture worldwide. Farmers and governments use these data to optimise irrigation, predict crop yields, detect disease outbreaks, and manage food security.

Deforestation & Land Use: Global Forest Watch uses Landsat and Sentinel data to detect deforestation in near real-time. Between 2001 and 2023, satellite monitoring documented the loss of 437 million hectares of tree cover worldwide.

Ocean & Maritime: Satellites monitor sea surface temperature, ocean colour (chlorophyll), ship traffic (AIS), illegal fishing, oil spills, and coral reef health. ESA's Sentinel-6 mission measures sea level with millimetre precision.

Air Quality: NASA's TEMPO, ESA's Sentinel-5P, and China's GEMS provide hourly measurements of atmospheric pollutants including NO₂, SO₂, ozone, and aerosols. These data help governments enforce clean air regulations and issue health warnings.