Fire Detection with the ATSR-2 Sensor

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Fire Detection with the ATSR-2 Sensor

• By Kurt Fischer
• ME 449

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Table of Contents

• 1) Introduction
• 2) Background on thermal radiance
• 3) Background on fire radiance
• 4) How the ATSR senses fires
• 5) Summary

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Introduction

• Objective To provide a concise explanation on
  how the ATSR-2 sensor, on the ERS-2 satellite ,
  detects fires.
• Rationale To achieve a better understanding in
  the interpretation of the ATSR fire location
  data.
• Method This collection of information was
  gathered from internet research that focused on
  NASAs remote sensing tutorial web site , and the
  European Space Agencys web site concerning the
  ATSR World Fire Atlas. The front page picture
  shows the ATSR World Fire Atlas for 1997 LINK.

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Thermal Emission Background

• By Plancks law, the emission spectra (emission
  intensity as a function of wavelength, l) depends
  on the absolute temperature, T degK of the
  object.
• The wavelength of maximum of the emission spectra
  can be found from the universal relationship
• (lT)max 0.29 cm degK.
• When the temperatures differ by 500C, these
  maximum relative intensities differ by an order
  of magnitude
• This large difference allows fires to standout
  from the background

Relative emission spectra of objects at different
temperature.
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Fire Radiance Background

• A fires temperature can range from 400 K to 1000
  K
• The respective maximum relative intensity occurs
  2-5µm
• This gives the optimum wavelength to use in order
  to see the fire
• The channel that is used on the ATSR-2 to detect
  fires is at 3.7µm (LINK)

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Satellite Sensing of Fires
Here is an example of two signals that would
saturate the sensor

• The satellite first views a pixel (1km2) using
  the channel at 3.7 µm
• It makes a record of the fire when a signal
  saturates the sensor
• The signals intensity must be high enough in
  order for saturation to occur
• Intensity is a function of temperature and area
• Saturation first occurs at around 320 K (given a
  large enough area)
• Must be done at night to avoid solar reflectance
  which would cause artefact signals
• Clouds will block the signal from fires (LINK)

See http//esapub.esrin.esa.it/eoq/eoq50/arino50.h
tm
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Processed Global Fire Location Data
This picture shows an example of fire counts in
North America in April of 1999 (LINK) What are
the dots? What does it show? Which month
etc?????????????
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Summary

• Fires can be detected because their temperature
  (400-1000K) is much higher relative to its
  surroundings.
• The range of high temperature radiates different
  wavelength bands with a maximum relative
  intensities occurring between 3 and 5
  µm.(sentence)
• The sensor, which is tuned to 3.7 µm, can detects
  fires because the radiance is much greater than
  that of the background at that wavelength.
• The sensors limitations include
• - solar glare fires can only be detected at
  night because solar reflectance will cause false
  signals (what are solar glare fires? Kurt, you
  got to read your stuff)
• - other objects with temperature similar to that
  of fire will be recorded as a fire cities often
  cause this type of misinterpretation
• - clouds will block the sensor from seeing the
  fire.