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The observation of high temperature events (HTE) is an important field of the remote sensing because of their influence on the global change of the environmental processes6. Currently a small satellite BIRD (Bispectral Infrared Detection) dedicated to this task is under development in the German Aerospace Center. Considering the restrictions of an 80kg satellite a bispectral infrared push broom scanner working in the Midwave and in the Thermal Infrared based on the latest technology of linear detector arrays was developed. The identical design for both infrared channels was realised to save resources and to guarantee the reliability Because of the limited number of elements per line a subpixel detecting concept was chosen to estimate the parameters of the HTE with a reasonable ground resolution and swath width. A special dual band optics and a compact sensor head design will ensure the required geometric stability. The subpixel measurement method for the hot spot detection requires a high detectivity and a large dynamic range. A special signal processing concept has been implemented at the sensor head controller.Recently the first airborne experiments were carried out together with a push broom scanner in the visible. During this experiments the sensor control, onboard signal processing and data transmission routines were tested.

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The primary mission objective of a new small Bi-spectral InfraRed Detection (BIRD) satellite is detection and quantitative analysis of high-temperature events like fires and volcanoes. An absence of saturation in the BIRD infrared channels makes it possible to improve false alarm rejection as well as to retrieve quantitative characteristics of hot targets, including their effective fire temperature and area and the radiative energy release. For pronounced fire fronts, the front length and radiative intensity (radiative energy release per 1 m of the front length) are additionally estimated. During more than 15 months of its operation, BIRD has detected numerous natural wild fires and volcanic events. The smallest man-made fires detected by BIRD, which were verified on-ground, had an area of 12 m 2 at daytime and 4 m 2 at night. BIRD MISSIONThe primary mission objective of a new small Bi-spectral InfraRed Detection (BIRD) satellite, which was put in a 570 km circular sun-synchronous orbit on 22 October 2001, is detection and quantitative analysis of high-temperature events like fires and volcanoes [1]. The principal BIRD imaging payload includes the Hotspot Recognition System HSRS with channels in the Mid-Infrared (MIR, 3.4 -4.2 µm) and Thermal Infrared (TIR8.5 -9.3 µm) spectral ranges and the Wide-Angle Optoelectronic Stereo Scanner WAOSS-B with a nadir channel in Near-Infrared (NIR: 0.84 -0.90 µm) and with two off-nadir channels that are currently not used for hotspot detection. The ground resolution of the BIRD nadir channels is 185 m in the NIR and 370 m in the MIR and TIR. However, all three channels have the same sampling step of 185 m due to a factor of 2 oversampling of the MIR and TIR data.A unique feature of the BIRD MIR and TIR channels is a real-time adjustment of their integration time [2]. If on-board processing of HSRS data indicates that detector elements are saturated, or close to saturation, in the first exposure then a second exposure is performed within the same sampling interval with a reduced integration time. This eliminates detector saturation over high temperature targets but preserves a 0.1-0.2 K radiometric resolution for pixels at normal temperatures [3].Due to the better resolution of the HSRS channels, BIRD can detect hot targets with a factor of 7 smaller area than MODIS and AVHRR. The oversampling of the BIRD