Fire Detection with the ATSR-2 Sensor

1. Fire Detection with the ATSR-2 Sensor By Kurt Fischer ME 449

2. Table of Contents 1) Introduction 2) Background on thermal radiance 3) Background on fire radiance 4) How the ATSR senses fires 5) Summary

3. 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 NASA’s remote sensing tutorial web site , and the European Space Agency’s web site concerning the ATSR World Fire Atlas. The front page picture shows the ATSR World Fire Atlas for 1997 LINK.

4. Thermal Emission: Background • By Planck’s 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 ~500*C, 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.

5. Fire Radiance Background • A fire’s 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)

6. 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 signal’s 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.htm

7. 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?????????????

8. Summary Fires can be detected because their temperature (400-1000K) is much higher relative to it’s 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 sensor’s 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.