Remote Sensing - a tool for environmental observation

Landsat 6 was extended with the etm the enhanced

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reached its orbit (a loss of US $220 million). Landsat 6 was extended with the ETM: the Enhanced Thematic Mapper. Apart from this ETM there was an eight band, a panchromatic channel (0.50 - 0.90 μm) with a spatial resolution of 15 m. It took another 6 years before Landsat 7 with aboard the ETM+ sensor was launched on 15 April 1999. Landsat 7 ETM+ is the successor of the very successful Thematic Mapper (TM) instruments on Landsat 4 and 5. Landsat 7 is equipped with six bands in the visible to shortwave infrared with a resolution of 30m, one band in the thermal infrared with a resolution of 60m and with a panchromatic band with a resolution of 15m. A permanent instrument malfunction occurred on May 31, 2003. The problem was caused by failure of the Scan Line Corrector (SLC), which compensates for the forward motion of the satellite. Since then only limited useful data is acquired in "SLC-off" mode (LANDSAT, 2003). SPOT: Système Probatoire d’Observation de la Terre The acronym of SPOT stands for ‘Earth Observation Test System’ and was the first earth observation satellite launched by an European country. It is developed and operated by the CNES: Centre National d’Études Spatials at Toulouse. SPOT has a near-polar, sun-synchronous, 832 k high orbit with a repeat time of 26 days. However, the direction of the sensors of SPOT can be changed up to 27 ° , enabling the SPOT-sensors to make oblique views of the earth (figure 2.4). This capability increases the repeat time considerable, up to several days. SPOT-1 was launched on 21 February 1986. SPOT-2 and SPOT-4 have already been launched with identical orbits and sensor systems. SPOT XS and SPOT PAN: Multi-spectral mode (XS): 1. 0.50 - 0.59 μm Altitude: 832 k 2. 0.61 - 0.68 μm Inclination: 98.7 ° 3. 0.79 - 0.89 μm Pixelsize: Panchromatic mode (PAN): Pan-mode: 10 m 0.51- 0.73 μm XS-mode: 20 m SPOT VEGETATION 1. 0.43 - 0.47 μm Blue Altitude: 832 k 2. 0.61 - 0.68 μm Red Inclination: 98.7 ° 3. 0.79 - 0.89 μm NIR Pixelsize: 1000 m at Nadir 4. 1.58 – 1.75 μm MIR
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30 The SPOT sensor is a pushbroom scanner, it does not have moving parts such as a rotating mirror. Instead it has an array of detectors and each scan line is sampled at one go. The spatial resolution is very large: the panchromatic mode has a pixel size of 10 m with a very high geometric accuracy. The VEGETATION sensor was added to SPOT 4. This instrument is mainly designed for monitoring vegetation dynamics at the continental scale but it is also useful for meteorological observation and oceanographic studies. VEGETATION has a swath of 2250 km wide and a spatial resolution of 1 km at nadir. A few spectral bands (blue and mid infrared) are added compared to the earlier, high-resolution SPOT-XS designs. Figure 2.4 An illustration of SPOT off-nadir viewing system (Curran, 1985). TERRA Platform On December 18, 1999, NASA launched Terra, its Earth Observing System (EOS) flagship satellite. It became operational in February 2000. In particular, the mission is designed to improve understanding of the movements of carbon and energy throughout Earth’s climate system (TERRA, 2005). Instruments aboard TERRA comprise ASTER for land surface
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