LEO SATELLITE GLOBAL FIRE DATA / 1 YEAR / NASA

LEO SATELLITE GLOBAL FIRE DATA

NASA's Fire Information for Resource Management System

NASA's Land, Atmosphere Near real-time Capability for EOS (LANCE) system

VIIRS

• The Visible Infrared Imaging Radiometer Suite (VIIRS) 375 m thermal anomalies / active fire product provides data from the VIIRS sensor aboard the joint NASA/NOAA Suomi National Polar-orbiting Partnership (Suomi NPP) and NOAA-20 satellites. The 375 m data complements Moderate Resolution Imaging Spectroradiometer (MODIS) fire detection; they both show good agreement in hotspot detection but the improved spatial resolution of the 375 m data provides a greater response over fires of relatively small areas and provides improved mapping of large fire perimeters. The 375 m data also has improved nighttime performance. Consequently, these data are well suited for use in support of fire management (e.g., near real-time alert systems), as well as other science applications requiring improved fire mapping fidelity.

MODIS

• The Moderate Resolution Imaging Spectroradiometer (MODIS) is a payload imaging sensor that was launched into Earth orbit by NASA in 1999 aboard the Terra (EOS AM) satellite and in 2002 aoard the Aqua (EOS PM) satellite. Please refer to the Near Real-Time Data FAQ section for more information about MODIS.

Acknowledgements

• The VIIRS sensor aboard the Suomi NPP satellite, crosses the equator at approximately 13:30 PM (ascending node) and 1:30 AM (descending node).
• The VIIRS sensor aboard the NOAA-20 satellite, crosses the equator approximately 50 minutes prior to Suomi NPP, at approximately 12:40 PM (ascending node) and 12:40 AM (descending node).
• The 3,040 km VIIRS swath enables ~15% image overlap between consecutive orbits at the equator, thereby providing full global coverage every 12 hours and mid-latitudes will experience 3-4 looks a day.
• VIIRS has 5 high resolution Imagery channels (I-bands), 16 moderate resolution channels (M-bands) and a Day/Night Band (DNB).
• The VIIRS detectors have a constant angular resolution that results in an increasing pixel footprint size as the scan is further from nadir (see figure 1 below). This means the actual area of each scan has the shape of a bow-tie, as consecutive scans overlap away from nadir. The bow-tie effect is reduced during processing through a combination of aggregation and deletion of overlapping pixels.

HOW

• Satellites take a ‘snapshot’ of events as they pass over Earth. Each hotspot/active fire detection represents the center of a pixel flagged as containing one or more fires or other thermal anomalies (such as volcanoes). For MODIS the pixel is approximately 1 km and for VIIRS the pixel is approximately 375 m. The “location” is the center point of the pixel (not necessarily the coordinates of the actual fire). The actual pixel size varies with the scan and track. The fire is often less than the size of the pixel. We are not able to determine the exact fire size; what we do know is that at least one fire is located within the flagged pixel. Sometimes you will see several active fires in a line. This generally represents a fire front.

• The FIRMS fire map is updated every 5 minutes, but please note that the data are derived from instruments onboard polar orbiting satellites (MODIS aboard Terra and Aqua and VIIRS aboard Suomi NPP and NOAA-20), and generally these have 2 overpasses a day (more towards the poles. FIRMS generally makes the data available within 3 hours of a satellite observation (on a best effort basis).

• Fire detection is performed using a contextual algorithm that exploits the strong emission of mid-infrared radiation from fires. The MODIS algorithm examines each pixel of the MODIS swath, and ultimately assigns to each pixel of the following classes: missing data, cloud, water, non-fire, fire, or unknown.

NOTE

• Standard data products are an internally consistent, well-calibrated record of Earth’s geophysical properties to support science. Near real-time (NRT) fire products are generated within approximately 3 hours of a satellite observation to meet the needs of the applications community. To facilitate this, a number of changes have been made to the standard processing approach: Data downlinked from the satellite are sorted, processed, and delivered in an expedited manner (as Session-based Production Data Sets).

• One key difference between the MODIS/Aqua NRT and Standard (Science Quality) Fire Products is the accuracy of the Fire locations (positions or geolocation). Unlike MODIS/Terra, VIIRS/Suomi NPP, and VIIRS/NOAA-20, the position of the Aqua satellite is not as well known when the NRT Fire Product is produced. Most of the time, the additional error introduced in the reported Fire location is small (< 100 m), but in some situations this position error may be large (several kilometers)

STUDY

• You will see 2 separate studies. The first covers the days between 2020-2021 and 2021-2022 globally. The second one is focused only on Turkey.

PARAMETERS

• Latitude
  Center of nominal 375 m fire pixel

• Longitude
  Center of nominal 375 m fire pixel

• Bright_ti4
  Brightness temperature I-4 VIIRS I-4 channel brightness temperature of the fire pixel measured in Kelvin. The brightness temperature of a fire pixel is measured (in Kelvin) using the MODIS channels 21/22 and channel 31. Brightness temperature is actually a measure of the photons at a particular wavelength received by the spacecraft, but presented in units of temperature.

• Scan
  The algorithm produces approximately 375 m pixels at nadir. Scan and track reflect actual pixel size.

• Track
  The algorithm produces approximately 375 m pixels at nadir. Scan and track reflect actual pixel size.

• Acq_Date
  Date of VIIRS acquisition.

• Acq_Time
  Time of acquisition/overpass of the satellite (in UTC).

• Satellite
  N= Suomi National Polar-orbiting Partnership (Suomi NPP),
  1=NOAA-20 (designated JPSS-1 prior to launch)

• Confidence
  This value is based on a collection of intermediate algorithm quantities used in the detection process. It is intended to help users gauge the quality of individual hotspot/fire pixels. Confidence values are set to low, nominal and high. Low confidence daytime fire pixels are typically associated with areas of sun glint and lower relative temperature anomaly (<15K) in the mid-infrared channel I4. Nominal confidence pixels are those free of potential sun glint contamination during the day and marked by strong (>15K) temperature anomaly in either day or nighttime data. High confidence fire pixels are associated with day or nighttime saturated pixels.

Please note: Low confidence nighttime pixels occur only over the geographic area extending from 11deg E to 110 deg W and 7 deg N to 55 deg S. This area describes the region of influence of the South Atlantic Magnetic Anomaly which can cause spurious brightness temperatures in the mid-infrared channel I4 leading to potential false positive alarms. These have been removed from the NRT data distributed by FIRMS.

• Version
  Version identifies the collection (e.g. VIIRS Collection 1) and source of data processing: Near Real-Time (NRT suffix added to collection) or Standard Processing (collection only).
  "1.0NRT" - Collection 1 NRT processing.
  "1.0" - Collection 1 Standard processing

• Bright_ti5
  I-5 Channel brightness temperature of the fire pixel measured in Kelvin.

• FRP
  FRP depicts the pixel-integrated fire radiative power in MW (megawatts). FRP depicts the pixel-integrated fire radiative power in MW (megawatts). Given the unique spatial and spectral resolution of the data, the VIIRS 375 m fire detection algorithm was customized and tuned in order to optimize its response over small fires while balancing the occurrence of false alarms. Frequent saturation of the mid-infrared I4 channel (3.55-3.93 µm) driving the detection of active fires requires additional tests and procedures to avoid pixel classification errors. As a result, sub-pixel fire characterization (e.g., fire radiative power [FRP] retrieval) is only viable across small and/or low-intensity fires. Systematic FRP retrievals are based on a hybrid approach combining 375 and 750 m data. In fact, starting in 2015 the algorithm incorporated additional VIIRS channel M13 (3.973-4.128 µm) 750 m data in both aggregated and unaggregated format.

• type
  Inferred hot spot type:
  0 = presumed vegetation fire
  1 = active volcano
  2 = other static land source
  3 = offshore

• DayNight
  D= Daytime fire,
  N= Nighttime fire