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Space remote sensing sensors

LifeWatch Wallonia-Brussels mainly relies on airborne and spaceborne sensors. Images from different sensors are used to take advantage of strengths of each type of sensor: high resolution images (5 to 30 m) are acquired every two weeks but coarse resolution (300 to 1000 m) images are taken every one to two days.

Moderate-resolution Imaging Spectroradiometer (MODIS) is an instrument launched into Earth orbit by NASA on board of two satellites (the Terra satellite in 1999 and the Aqua in 2002 satellite). Terra MODIS and Aqua MODIS are viewing the entire Earth's surface every 1 to 2 days, acquiring data in 36 spectral bands. These data are improving our understanding of global dynamics and processes occurring on the land, in the oceans, and in the lower atmosphere. Two products derived from this instrument are used to describe fires (MCD64A1) and snow (MOD10A2).

SPOT VEGETATION is an instrument on board of SPOT 4 (1998-2013) and SPOT 5 (2002-2014). This instrument delivers measurements specifically tailored to monitor land surfaces' parameters with a frequency of about once a day on a global basis and a medium spatial resolution of one kilometre. The continuity of the VEGETATION program is ensured by the Belgian microsatellite Proba-V, launched May 7, 2013 and the Sentinel-3 satellite as part of the Copernicus (launch planned for 2015) initiative. SPOT VEGETATION images are used to describe vegetation phenology based on NDVI.

Five RapidEye satellites form a constellation producing 5 meter resolution multi-spectral imagery. Each sensor is capable of collecting image data in five distinct bands of the electromagnetic spectrum: Blue (440-510 nm), Green (520-590 nm), Red (630-690 nm), Red-Edge (690-730 nm) and Near-Infrared (760-880 nm). The Red-Edge band is very useful to monitor vegetation health and improve species separation. RapidEye Images are used in the development of the ecotopes database to improve the classification of the land cover.

Landsat program is a running program for acquisition of satellite imagery of Earth since 1972. Images from Landsat 7 (1999) and 8 (2013) are used. Images are delivered per each satellite every 16 days. Landsat 7 has eight spectral bands with spatial resolutions ranging from 15 to 60 meters whereas Landsat 8 eleven spectral bands with spatial resolutions ranging from 15 to 60 meters. In addition to the visible and infra-red bands for reflectance, they also provide thermal infra-red emitted by the Earth surface. Regular revisits (16 days) allow to use Landsat images to get temporal information about the land cover within the ecotopes database.

Sentinel 2 (planned in 2015) will provide multi-spectral (13 bands, including visible, near and medium infra-red as well as 2 red-edge bands) high-resolution optical observations ranging from 10 to 100 meters over global terrestrial surfaces every ten days. Optical features will allow the use of images for land services (e.g. imagery of vegetation, soil and water cover, inland waterways and coastal areas). A second satellite will be launched soon after the first. The combination of both will provide temporal information thanks to a revisiting period of 5 days, which will improve the classification and the segmentation of the ecotopes.

Sentinel 2 satellite (©ESA)