How satellites detect wildfires
Modern wildfire detection relies primarily on two NASA satellite instruments: MODIS (Moderate Resolution Imaging Spectroradiometer) aboard the Terra and Aqua satellites, and VIIRS (Visible Infrared Imaging Radiometer Suite) aboard Suomi NPP and NOAA-20. These instruments detect thermal anomalies — unusually hot spots on the Earth's surface — by measuring infrared radiation at specific wavelengths.
When a fire burns, it emits energy in the mid-infrared spectrum at levels far above the surrounding landscape. Satellite sensors pick up these thermal signatures and flag them as active fire detections. The process happens automatically: the satellite passes over, captures the scene, downlinks data to ground stations, and algorithms identify fire pixels within hours.
NASA FIRMS and the EONET fire catalog
NASA's Fire Information for Resource Management System (FIRMS) distributes active fire data from MODIS and VIIRS globally. The data is updated multiple times per day and includes fire radiative power (FRP) — a measure of how much energy the fire is releasing. Higher FRP generally means a more intense or larger fire.
On PlanetSentry, wildfire events from NASA EONET appear as markers on the 3D globe. Each marker links to the source event page and includes geometry, timeline, and supporting satellite imagery overlays. Because EONET groups related detections into named events (like a specific forest fire that burns for days or weeks), users can follow a wildfire's lifecycle instead of looking at disconnected hotspot pixels.
- MODIS: 1 km resolution, twice-daily global coverage from Terra and Aqua
- VIIRS: 375 m resolution, more frequent coverage from Suomi NPP and NOAA-20
- FIRMS updates: near-real-time data available within 3 hours of satellite overpass
- Fire Radiative Power (FRP): energy output metric useful for comparing fire intensity
Interpreting false-color fire imagery
When you switch to a fire-related imagery layer on PlanetSentry, the colors are not what a human eye would see from space. False-color composites boost shortwave infrared bands to make active fire fronts, recently burned areas, and thermal anomalies visually obvious. Bright reds and oranges typically indicate active heat, while darker tones show burned or cooling ground.
The most common mistake is treating these layers as photographs. A bright orange patch might be a massive fire, but it could also be hot bare earth, a city heat island, or an artifact of the color ramp. Always cross-reference with the event catalog and check the imagery date stamp before drawing conclusions.
Building a wildfire watch routine
If you monitor wildfires regularly — for journalism, research, insurance assessment, or personal awareness — establish a repeatable routine. Open PlanetSentry daily, filter to the wildfires category, check the globe for new event clusters, and read the detail panels for events in your regions of interest. Compare current satellite imagery against the previous week to see how fires are expanding or contracting.
For deeper analysis, follow the EONET event link to the source page, check FIRMS for the latest hotspot data, and look at wind and humidity overlays to understand how weather conditions are influencing fire behavior. This layered approach turns a quick glance into genuine situational awareness.