The main purpose of the FireBIRD mission is to detect high temperature events (HTE). These are often forest fires, which may be caused by lightning as part of a natural cycle, or, more frequently, by people for clearing purposes or due to arson. A good example for the interaction of human and climate factors are the forest fires in Indonesia during the 1997-1998 El Niño period. These were in most cases caused by clearing activities, although their expansion and duration were significantly facilitated by the aridity accompanying El Niño in this region. Climatic influences on forest fires are also evident at higher latitudes. For example, in the past 20 years forest fires in the boreal forests of western North America have doubled in frequency and correspond to the observed warming of this region. Similar observations have been made in the forested regions of Eurasia. Although intensive measures have successfully prevented major fires in Scandinavia, in the past few decades 5-10 million hectares of forest have been lost to fire in circumpolar boreal regions.
Vegetation fires give rise to aerosols; an assortment of gases such as carbon dioxide, carbon monoxide, and nitrogen oxides; and particles of various sizes. The release of gases and particles in forest fires depends on numerous parameters, such as the particular fuel involved, the type of combustion, and the weather situation (wind, ground moisture). Aerosols from forest fires influence the weather and climate in complex and diverse ways. Some of the liberated particles function as nuclei on which water vapour condenses to form cloud droplets. This has a variety of consequences. The presence of more cloud droplets increases the reflection of sunlight back to space, which has a cooling effect. Small cloud droplets have a lower rate of fall than large ones, so biomass burning changes the likelihood of rain and other forms of precipitation. It is anticipated that climate change caused by human activities will lead to an increase in the frequency of forest fires in the next few decades, especially in places experiencing a marked increase in temperature while precipitation remains constant or is reduced. Whereas recently it has been primarily in the tropics where forests have been lost to fire, in the future forests in the temperate and boreal zones will be much more affected than at present. This is especially the case for the large forested regions of Canada and Russia. If the carbon dioxide concentration doubles, it is assumed that winter temperatures will increase by 6-10 °C and summer temperatures by 4-6 °C. Even if precipitation should increase, it will be more than compensated by increased evaporation. According to model calculations, this will cause the fire season to begin earlier, and large areas will be seriously threatened by fire already in May (in Canada 0.5 million. km2, in Russia over one million km2), which up until now was the case for only a very small area. Especially in the summer months, particularly June and July, the extent of areas with a very high or extremely high risk of forest fires will significantly increase.
Already for several years, satellites with global coverage have been used to estimate the parameters mentioned above (for example, data from the MODIS, METEOSAT, CALIPSO, ADM, and EarthCARE satellites). However, a serious disadvantage of the available sensors is their relatively poor spatial resolution, at best 1 km per pixel. This means that only fires that radiate over 10 megawatts (= flaming vegetation fires with areas of ca. 200 m2) can be reliably detected. Thus up to half of all fires are missed with available satellite systems. The German FireBIRD Mission with the two satellites TET-1 and BIROS is designed to significantly reduce the gaps and uncertainties. Together with the systems already in orbit, mentioned above, TET-1 and BIROS will contribute something like a magnifying glass to the search for fires. On the one hand they will close the important gap consisting of the high number of undetected small fires (with upward radiation from 1 MW to 10 MW), so that many more fires can be detected and accordingly recorded in the emissions inventory. On the other hand, the TET-1/BIROS mission will be used to validate and fine tune emission estimates based on data of lower spatial resolution, collected for example by geostationary satellites at short temporal intervals. Both satellites benefit from the technical expertise gathered by DLR in the BIRD mission of 2001 to 2004. BIRD was developed by the DLR Institute of Optical Sensor Systems in Berlin and provided impressive recordings of small and large fires worldwide. The smallest fire detected by BIRD had an area of 12 m2.
Applications in addition to detecting and monitoring forest fires include: