Fire Detectives In Orbit: Using Remote Sensing To Detect Wildfires

By Jason Palidwar, Claude Montcalm, and Peter Hook, Iridian Spectral Technologies

Saving lives, land, and property hinges heavily on early discovery of fires that often start in remote areas and remain undetected until they have grown catastrophically, as well as early recognition of the conditions that can lead to wildfires. Advances in optical technology, combined with changing launch cost dynamics, have pushed optical Earth observation (EO) to the forefront of wildfire detection, tracking, and management.

The application of EO to early remote detection of wildfires typically offers two key approaches. First, observers can attempt to identify chemical absorption bands of interest, such as potassium, that can be indicative as precursors to wildfire. More common is the use of thermal imaging to look for hot spots, or specific types of heat profile, in longwave infrared (LWIR) bands from space. Multispectral imaging systems can combine these approaches into one unit.

To achieve multiband detection, one can place a multizone filter on top of a detector, in close proximity, to where each zone of the filter will transmit a particular wavelength region onto the detector surface. Each strip, or zone, usually translates into a different gas/element/constituent being detected. However, the detector is a fixed area, so the more zones in that area, the narrower the band, and the fewer pixels assigned to each one — which can limit the signal relative to the background for each band.

Thus, designers must navigate the tradeoffs between what they want to detect and any limitations imposed by the detector itself. Dropping a noncritical band or two from the design can improve signal quality for the other bands as well as help to optimize cost for the satellite creator/operator.