RESEARCH LETTER 2.10

www: satellitefires

This Letter is inspired by the launching of a new web site devoted to the display of fire ‘hot spots’ detected by satellite - www.sentinel.csiro.au. ‘Hot spots’ are the locations of burning material, including bushfires. ‘Hot spots’ can be flares from oil and gas fields or refineries but these stationary sources are screened out in this case. A big bushfire will have many hotspots, the number depending on the resolution of the satellite.

The aim of the website is to display fire ‘hot spots’ within one hour of the pass of the satellites concerned - the TERRA satellite (http://terra.nasa.gov/ ) and the AQUA satellite (http://eos-pm.gsfc.nasa.gov/). Together these satellites pass overhead 4 times per day.

The sensor for ‘hot spots’ on both the TERRA and AQUA satellites is the MODIS (Moderate Resolution Imaging Spectroradiometer) sensor. “Moderate resolution” means 250m to 1 km sides to pixels are the norm. For more about the instrument see http://aqua.nasa.gov/MODIS3.html. See pictures of fire areas and dust clouds over Australia at http://visibleearth.nasa.gov/Sensors/Terra/MODIS.html (search for “fire Australia”).

Upon opening the web site at www.sentinel.csiro.au, click on ‘go to maps’ then acknowledge the disclaimer. Tick the square boxes on the right, refresh the map by clicking on the appropriate button, then repeatedly zoom in on the area of interest (click on a site on the map or use the ‘zoom in’ button and cursor to draw a rectangle around the area of interest). As you zoom in further and further you should reach the stage where there is a map with place names, roads and railways to be seen on the screen. Then the site of the ‘hot spot’ is easy to see. If you then click on the Active spot (open circle) next to “hot spots by date”, highlight the button marked “Identify” (lower left of screen) and move the cursor (cross hairs) onto the ‘hot spot’ of interest then click, a box revealing the exact location, the time of observation and the satellite concerned will be revealed at the bottom of the screen. It’s mostly self explanatory.

Another Australian website for fires detected from space is that of the Western Australian Department of Land Administration, DOLA. See www.rss.dola.wa.gov.au/. DOLA uses the evening overpasses of NOAA satellites to detect ‘hot spots’. It routinely advises graziers and others in Western Australia and in the Northern Territory of the whereabouts of ‘hot spots’. DOLA have recently opened a MODIS service also.

Satellite systems are not perfect, hence ‘hot spots’ (or ‘fire hot spots’ to designate purpose) rather than ‘fires’. There are fires missed and fires falsely declared by ‘hot spots’. Cloud obscures fires for example. For an evaluation of the NOAA technology see http://www.ea.gov.au/soe/techpapers/fire/index. [You may have to go to ‘Environment Australia’ and ‘State of the Environment’ and ‘Biodiversity’ and ‘Australian Fire Regimes 2002’]. The NOAA system operates best in flat areas at low latitude with a good view of the ground for the fire season – as in the tropical savanna. It is least effective in places like Tasmania. It is obvious, but easily forgotten, that the observation of fires can only be possible when the satellite is passing over the area of interest, and is operating, so continuous observation of fires is not yet possible.

Satellite systems have the potential to not only detect running fires but also to map their intensities. For fire detection and possible intensity measurement check out the BIRD (Bi-spectral Infrared Detection) Satellite at http://spacesensors.dlr.de/SE/bird/ (Have a look at some scenes of NSW fires and a comparison with MODIS). Intensity measurement is in its infancy so it is as well not to rely on the measurements. Ground calibration is necessary.

Satellites are ideal for the mapping of the plumes of gases emanating from fires. This information is valuable for those studying climate change. A sensor on the TERRA satellite called MOPITT measures CO (carbon monoxide) and an example (not Australian) can be seen on http://visibleearth.nasa.gov/Sensors/Terra/MOPITT.html.

There are many satellites now used for fire studies. They have various sensors detecting various items at various scales at various intervals with varying success. They need ground testing to validate them. While this is easiest for ‘burned area’ the world-wide remote-sensing community would welcome co-operation from agencies which actually measure and record locations of burned areas on the ground (for example). A national mapping program in which satellites would play a part is needed if we are to improve our understanding of the ecology of the continent, assess the State of the Environment better, assess Greenhouse Gas emissions, and better determine Standards of Fire Cover and Fire Threat.

A. Malcolm Gill

19th December 2002