Satellite Fire Data Products

This page summarizes the main satellite fire data products from MODIS, VIIRS, and GOES, with focus on Level 2 Active Fires. The goal is practical: to understand what the data contain, how they are structured, and how to use them.

Processing Levels

**Level 1 (L1B)**: Calibrated, geolocated radiances at native resolution.
**Level 2 (L2)**: Derived geophysical variables at the same resolution as L1 (e.g., fire masks, Fire Radiative Power).
**Level 3 (L3)**: Gridded or time-composited variables on standard grids (e.g., daily fire counts per 0.25° cell).

Key Geometry Terms

**Swath**: The cross-track stripe observed as the sensor scans.
**Granule**: The basic time chunk of data (e.g., 5–6 minutes for polar orbiters; 1–10 minutes for GOES sectors).
**Pixel**: One sample from the sensor. Pixel size depends on instrument and grows off-nadir. VIIRS mitigates this with aggregation and "bow-tie deletion."

MODIS Active Fires (Terra and Aqua)

**Satellites**: Terra (morning \~10:30, drifting earlier), Aqua (afternoon \~13:30).
**Orbit**: Sun-synchronous near-polar, \~705 km altitude.
**Swath and granules**: 2330 km wide swath, \~5 min granules.
**Resolution**: 1 km at nadir, coarser off-nadir.
**Products**: MOD14 (Terra), MYD14 (Aqua).
**Fields**: Fire mask (low/nominal/high confidence), confidence 0–100%, FRP (MW), brightness temperatures, view geometry.
**Revisit**: Two daily looks at mid-latitudes from both satellites combined.

VIIRS Active Fires (S-NPP, NOAA-20, NOAA-21)

**Satellites**: Three polar orbiters in the JPSS constellation.
**Orbit**: \~824 km altitude, \~13:30 LT ascending node.
**Swath and granules**: 3060 km swath, 6 min granules.
**Resolution**: 375 m (I-band), 750 m (M-band).
**Products**: VNP14IMG (S-NPP), VJ114IMG (NOAA-20), VJ214IMG (NOAA-21).
**Fields**: Fire mask, confidence %, FRP (MW), brightness temps, geometry.
**Revisit**: Multiple looks/day, with \~25–50 min spacing between satellites. Both day (\~13:30) and night (\~01:30) coverage.

GOES ABI Fire/Hot Spot Products

**Satellites**: GOES-East (GOES-19), GOES-West (GOES-18).
**Orbit**: Geostationary at \~35,786 km.
**Resolution**: 2 km at nadir for IR band 7 (3.9 µm).
**Cadence**: 10 min full disk, 5 min CONUS, 1 min mesoscale.
**Product**: Fire/Hot Spot Characterization (FHS/FDC).
**Fields**: Fire mask codes (10/30 high confidence, 11/31 saturated, 12/32 cloud-contaminated, 13–15/33–35 lower probabilities), FRP (MW).
**Notes**: Use mask codes 10,11,30,31 for conservative detection. Pixel locations not terrain-corrected, so offsets over mountains occur.

Complementarity

**MODIS**: Coarser (1 km) but long record since 2000; provides morning and afternoon views.
**VIIRS**: Finer (375 m), more frequent coverage with three satellites.
**GOES**: Coarser (2 km) but provides rapid updates (1–10 min), enabling near-real-time fire behavior monitoring.

Practical Usage Tips

Filter by confidence: MODIS/VIIRS high-confidence or ≥80%; GOES codes 10,11,30,31.
Account for off-nadir pixel growth and location errors.
Match granule timing to incident timelines (5 min MODIS, 6 min VIIRS, 1–10 min GOES).
FRP is in MW per pixel, but uncertainty varies (higher for GOES lower-confidence classes).

References

MODIS Active Fire Product (Collection 6.1): [1](https://lpdaac.usgs.gov/products/mod14v061/)
VIIRS 375 m Active Fire Product: [2](https://lpdaac.usgs.gov/products/vnp14imgv001/)
VIIRS Algorithm Theoretical Basis Document: [3](https://lpdaac.usgs.gov/documents/197/VNP14_User_Guide_V1.pdf)
GOES ABI Fire/Hot Spot Characterization: [4](https://www.ospo.noaa.gov/Products/atmosphere/fire/)
NASA EOSDIS Data Processing Levels: [5](https://earthdata.nasa.gov/faq/data-processing-levels)