Satellite Fire Data Products: Difference between revisions
(from ChatGPT 5. Prompt: Provide a technical explanation of fire data products from satellites, particularly MODIS, VIIRS, GOES, with focus on Level 2 Active Fires data, concept of swath, granules, pixels, their numerical values, revisits, orbit design. Summarize differences between Level 1, 2 and 3 data. Approach: practical, for someone who needs to use and understand the data. Provide original references with links. Provide as a file for a simple wikimedia instal.) |
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=== Processing Levels === | === 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 === | === 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) === | === 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) === | === 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 === | === 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 === | === 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 === | === Practical Usage Tips === | ||
Revision as of 05:51, 27 August 2025
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)