Xerra News Cat

Beneath the smoke of bushfires

By January 7, 2020 No Comments

By using satellite imagery collected in the infrared part of the spectrum scientists can often trace the fire-fronts in bushfires, despite the thick layers of smoke blanketing the area. That is, in the infrared we can see through the smoke, which can help determine how and where the fires are burning. We expect this is what many of our Australian colleagues are doing at this moment as support to emergency services.

The images supplied here were collected by the European Sentinel-2A satellite on a pass over New South Wales, Australia on January 3rd, and processed by our scientists here at Xerra.

The image below is a ‘normal’ colour mix for the region around Jervis Bay, Nowra and Ulladulla, south of Sydney on the NSW coast. That is, this image is similar to what an astronaut might see (and photograph using a regular camera) from the Space Station.

Sentinel-2A satellite image of part of the NSW coast obtained on January 3rd with a ‘normal’ colour mix of the red, green and blue bands of the visible spectrum. In this image, the smoke obscures the fire-fronts that lie below.

By using an image obtained by the same satellite but at a wavelength of 2.2 microns (in the short-wave infrared [SWIR] part of the electromagnetic spectrum), one sees something quite different, as below.

A SWIR image of the same region as in the preceding image, scaled from black (low intensity) to yellow/orange (high intensity). In the SWIR the sensor ‘sees’ through the clouds and smoke, and detects the radiation being emitted by the active fires.

Clouds obscure our ability to see the actual fires in the visible part of the spectrum, so that all we see is reflected sunlight. Whereas in the infrared, we can not only see through the clouds but also we can see the electromagnetic radiation being emitted by the active fires.

*Data or imagery, such as the Sentinel images above are freely available from Xerra Gateway, for the use of researchers and others in New Zealand.