FireBIRD satellites – a duo on course for early fire detection

FireBIRD for early detection of forest fires
FireBIRD for early detection of forest fires
Image 1/1, Credit: DLR (CC-BY 3.0).

FireBIRD for early detection of forest fires

The small satellite BIROS (Bispectral InfraRed Optical System) and TET-1 (Technology Experiment Carrier) form a highly efficient pair for the early detection of forest fires in the FireBIRD (Fire Bispectral InfraRed Detector) mission. Their innovative infrared sensor system allows the satellites to precisely measure the spatial expansion and heat development of fires.

The FireBIRD mission is made up of two satellites, TET-1 (Technology Experiment Carrier) and BIROS (Bi-spectral InfraRed Optical System). They circle the Earth in a polar orbit, passing over the poles at an altitude of 500 kilometres.

These orbits are also called sun-synchronous orbits because the satellites always cross the equator at the same time. For TET-1, this is at 11:30, and for BIROS, 09:30. The satellites have been placed in a half orbit of each other, so that one passes the zeroth latitude from North to South at 9:30, whilst the other changes from the southern to the northern hemisphere at 11:30. It takes them 90 minutes to complete one orbit, totalling 16 longitudinal orbits per day. In 20 days, they have swept the entire Earth's surface area, along all latitudes, using their highly sensitive optical systems. They move together in a free constellation, meaning they are not in fixed formation, as was the case for the satellites in the TanDEM-X mission.

The core of both FireBIRD orbiters

Main payload of FireBIRD satellites the HSRS
Main payload of FireBIRD satellites. The Hot Spot Recognition System (HSRS) consists of one optical and two infrared cameras.
DLR

Both satellites are equipped with the same camera systems. These consist of one optical and two infrared cameras forming the Hot Spot Recognition System (HSRS). The bi-spectral infrared optical system (left and right opening) is made of two identical infrared sensors. They only differ in the spectral range for which they have been calibrated. One sensor detects electromagnetic waves in the mid-infrared, the other is calibrated within the thermal infrared range.

The optical sensor also covers the visible spectral range. This camera produces higher resolution than the infrared sensors and can be used for a more accurate identification of the geographical location of thermal images. In addition, the image taken by the optical camera must first be approximated by applying a diminutive algorithm to the infrared image.

This does not mean that the HSRS resolution is low, however. To compare: If the infrared sensor of MODIS, a moderate resolution imaging spectroradiometer on a NASA satellite, has a range of 1000 metres, then the infrared cameras on the FireBIRD satellites have a range on the ground of just 178 metres.

Main payload of FireBIRD satellites: the HSRS
The lenses of the three cameras in frontal view .
DLR

In addition to spatial resolution, the sensitivity of the sensors is also greater than previous systems: For example, the MODIS system and VIIRS (NASA), are already detecting hot spots from 10 megawatts onwards; FireBIRD satellites are gathering data from high-temperature events from one megawatt onwards. This means that small high-temperature events can also be detected, including those with low heat generation. The use of two cameras in two spectral ranges also enables the detection of fires that are considerably smaller than the ranges. Even if a pixel is still the size of six football pitches, fires the size of the centre circle are being detected. Chemical heat generation and smouldering fires can also be located.

Overview of the central parameters of the optical and IR cameras on TET-1 and BIROS

Optical cameraInfrared camera
Wavelengths380 to 750 nanometres3.4 to 4.2 micrometres and
8.5 to 9.3 micrometres
Focal distance90.9 millimetres46.39 millimetres
Visual field19.6 degrees19 degrees
F-number3.82.0
Pixel size7 x 7 micrometres30 x 30 micrometres
Number of pixels3 x 5,1642 x 512
Ground sample distance42.4356 metres
Scan range42.4178 metres

Both orbiters are based on the same bus concept. The satellite bus is the supply unit on board that ensures operation and also the payload: Solar panels are responsible for the energy supply. The tri-axial position provides a stable basis for this. The mobility of the three axles also provides them with a higher level of flexibility when selecting a target.

Contact
  • Philipp Burtscheidt
    Editor
    German Aerospace Center (DLR)
    Media Relations
    Telephone: +49 2203 601-2323
    Fax: +49 2203 601-3249
    Linder Höhe
    51147  Cologne
    Contact
  • Stephanie Kaufhold
    German Aerospace Center (DLR)

    DLR Institute of Optical Sensor Systems, Department Public Relations
    Telephone: +49 30 67055-636
    Linder Höhe
    51147  Köln

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