A quiet revolution in overhead observation
Two decades ago, access to satellite imagery during a disaster was restricted to governments, military agencies, and a handful of well-funded research institutions. Today, anyone with an internet connection can access near-real-time satellite data from dozens of sensors covering the entire planet multiple times per day. This transformation happened not through a single breakthrough but through a series of policy decisions to make publicly funded satellite data freely available.
The European Union's Copernicus program distributes data from the Sentinel satellite constellation at no cost. NASA's Landsat archive — over 50 years of continuous Earth observation — became freely available in 2008. NOAA shares GOES and JPSS data in real time. Japan, India, and China have followed with their own open data initiatives. The result is an unprecedented volume of freely accessible Earth observation data.
What the data shows during disasters
Sentinel-1 SAR imagery can map flood extent through cloud cover — a critical capability since many flooding events occur during overcast weather that blocks optical satellites. Sentinel-2 and Landsat provide multispectral imagery for burn scar mapping, vegetation health assessment, and land surface change detection. MODIS and VIIRS provide daily global coverage for fire detection, aerosol monitoring, and sea surface temperature.
During a major disaster, these satellite systems provide complementary views. An earthquake might be assessed using SAR interferometry to map ground deformation, optical imagery to identify damaged structures, and thermal infrared to detect fires. A wildfire is tracked through active fire detections, burn scar mapping, and smoke plume observation. No single sensor captures everything — the power is in the combination.
Speed improvements transforming operational use
The latency between satellite observation and data availability has compressed dramatically. MODIS active fire detections are available within 3 hours of observation. Sentinel-1 SAR data is accessible within 1–3 hours. Geostationary weather satellite imagery updates every 10–15 minutes. These near-real-time timelines make satellite data operationally useful during rapidly evolving events.
Cloud-based processing platforms like Google Earth Engine, Microsoft Planetary Computer, and Copernicus Data Space Ecosystem eliminate the need to download massive datasets. Analysts can process terabytes of satellite imagery in the cloud and produce derived products — flood maps, fire perimeters, deforestation alerts — within hours of an event rather than days or weeks.
PlanetSentry and the open data ecosystem
PlanetSentry is built entirely on open data sources — NASA EONET, USGS earthquake feeds, NOAA weather data, GDACS alerts, and Copernicus atmospheric monitoring. The platform exists because of open data policies. Without freely available APIs and satellite-derived products, building a global monitoring surface would require budgets only available to national agencies.
This dependency on open data is not a limitation — it is a feature. Open data means transparency, reproducibility, and the ability for anyone to verify what PlanetSentry displays. It also means the platform improves as the underlying data ecosystem improves. New satellite missions, faster processing pipelines, and expanded API capabilities automatically enhance what PlanetSentry can offer.
What remains unavailable
Despite the revolution in open satellite data, significant gaps remain. Very high-resolution commercial imagery (sub-meter) is not freely available and remains essential for detailed damage assessment. Radar satellite tasking for emergency acquisitions still requires formal activation through mechanisms like the International Charter. Some countries restrict distribution of high-resolution data over their territories.
The trend, however, is clearly toward greater openness. The EU's upcoming Copernicus Sentinel Expansion missions will add new capabilities. NASA's upcoming NISAR mission will provide freely available radar data at unprecedented resolution. The trajectory suggests that within a decade, the volume and quality of freely available satellite data will exceed what was available only to classified programs just twenty years ago.