Some days ago Chile has faced the worst forest fire in its history (see https://www.theguardian.com/world/gallery/2017/jan/25/chile-wildfire-worst-ever-in-pictures). First fires have been detected on January 19th, south off Santiago, and up to January 24th they spread southward, destroying more than 600 sq miles of land with thousands of people evacuated from their homes.
Sentinel 3-A mission managed to capture all the fire evolution and spreading over the last week thanks to OLCI and SLSTR instruments.
SLSTR instrument allows us to localize the fires position thanks to their thermal response. Thermal IR is emitted terrestrial energy, received from the sun and absorbed. According to Wien’s Law the maximum emission of energy from a body occurs at a wavelength inversely proportional to its temperature: for forest fire (temperature around 600K) the peak is corresponding c/a to 4 µm.
Here below three animated gifs created with two OLCI images (visible bands) vs SLSTR thermal response at 3.78 µm. The first gif is generated with two products acquired on January 20th, the second one with images acquired on January 24th: the thermal images perfectly display the fire spots, highlighted in red.
Finally the third gif is composed by 4 OLCI images and shows the fire evolution over 5 days and its spreading to the southern part of the Country.
https://scihub.copernicus.eu S3A_OL_1_EFR____20170119T141730_20170119T142030_20170119T154622_0179_013_224_3600_SVL_O_NR_002.SEN3 S3A_OL_1_EFR____20170120T135119_20170120T135419_20170120T154208_0179_013_238_3600_SVL_O_NR_002.SEN3 S3A_OL_1_EFR____20170123T141345_20170123T141645_20170123T160541_0179_013_281_3599_SVL_O_NR_002.SEN3 S3A_OL_1_EFR____20170124T134735_20170124T135035_20170124T152926_0180_013_295_3599_SVL_O_NR_002.SEN3 S3A_SL_1_RBT____20170120T135119_20170120T135419_20170120T153332_0179_013_238_3600_SVL_O_NR_002.SEN3 S3A_SL_1_RBT____20170124T134735_20170124T135035_20170124T152830_0179_013_295_3599_SVL_O_NR_002.SEN3