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Remote Sensing - a tool for environmental observation

Landsat mss landsat tm and landsat etm the american

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Landsat MSS, Landsat TM and Landsat ETM+ The American Landsat series of satellites were developed within the ‘Earth Resources Programme’ of NASA in the early seventies. The first Landsat satellite was launched on 22 July 1972. At that time it was called ERTS-1: Earth Resources Technology Satellite. Later on this name was changed into Landsat-1. This satellite was of great importance because it provided many, high quality beautiful images which gave remote sensing technology world-wide recognition. The Landsat satellites all carry or have carried aboard a multi-spectral scanning system MSS. The later versions had/have also a Thematic Mapper: TM. Landsat 1 and 2 carried in addition a return beam vidicon (RBV) television camera. Figure 2.2. shows the two satellites, they approximate the size of a small car. The Landsat satellites are in an orbit at an altitude of approximately 900 km (later lowered to 700 km) and the MSS and TM sensors provide images of 185 by 185 km. MSS provides images in 64 grey levels (6 bits), TM sends down images in 256 grey levels (8 bits). The TM was an improvement of the earlier MSS sensor, it has more spectral bands and an increased spatial resolution (table 2.1). The Landsat satellites have a sun-synchronous orbit with an inclination of 98.2 ° , they require approximately 100 minutes to circle the earth and they have a repeat time of 16 days i.e. they make an image of the same area every 16 days (figure 2.3). Table 2.2 gives an overview of sensors and their spatial resolution aboard the Landsat satellites. Note the differences in pixel size: MSS: ± 80 m, TM: 30 m, TM-thermal: 120 m.
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27 Band μm Application ──────────────────────────────── 1 0.45-0.52 Blue: Designed for water body penetration (coastal waters) 2 0.52-0.60 Green: designed to measure green reflectance peak of vegetation for crop and vegetation discrimination. 3 0.63-0.69 Red: designed to sense in chlorophyll absorption bands for species differentiation. 4 0.76-0.90 Near infrared: useful for determining vegetation types, vigour and biomass content and for delineating water bodies. 5 1.55-1.75 Short-wave infrared: Indicative of vegetation moisture content and soil moisture. Useful to discriminate clouds from snow. 6 10.4-12.5 Thermal infrared: Useful in vegetation stress analysis, soil moisture mapping and thermal mapping. 7 2.08-2.35 Short-wave infrared: Useful for discrimination of mineral and rock types. Also sensitive for vegetation moisture content. Landsat ETM+: Same configuration as Landsat TM except that the following band (8) was added: 8. 500 – 900 nm (Panchromatic) 15 by 15 meter Table 2.1 Thematic Mapper Spectral bands. Figure 2.2 The two Landsat satellites. The left one is the Landsat 1, 2 and 3. The right one is the Landsat 4, 5 and 6. (Curran, 1985).
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28 Figure 2.3 Sun-synchronous orbit of Landsat 4 and 5 (CCRS tutorial & Lillesand & Kiefer, 2000).
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29 The first 5 Landsat satellites were very successful. Unfortunately, the launching of Landsat-6 came to a bad end. Immediately after launch radio contact was lost and the satellite never reached its orbit (a loss of US $220 million). Landsat 6 was extended with the ETM: the
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