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| | | | | | | | | Landsat image of Hubbard Glacier in southeastern Alaska | |
Landsat
The Landsat series has produced seven satellites so far. The first three were equipped with multispectral scanners (MSS) with a spatial resolution of 79 metres and a spectral resolution of 4 channels in the visible and near infrared ranges.
Landsat 4 and 5 are also equipped with a Thematic Mapper (TM) in addition to a Multispectral Scanner instrument. The Thematic Mapper has seven channels, including one thermal infrared band. The spatial resolution of all but the thermal band is 30 metres - this means that each pixel represents an area of the Earth's surface 30 metres by 30 metres. The thermal band has a spatial resolution of 120 metres.
Landsat 7 carries an Enhanced Thematic Mapper (ETM+). This instrument is similar to the TM except that the thermal band has a spatial resolution of 60 metres, and there is an 8th band which is panchromatic. This panchromatic band has a spatial resolution of 15 metres and can be used to enhance the spatial resolution of the multispectral bands. On 31 May 2003, the Scan Line Corrector (SLC) in the ETM+ instrument failed. The resulting effect is that approximately a quarter of the data in each ETM+ scene since the time of the SLC failure is missing, and the images appear stripy.
| | False colour composite image of area near Silkeborg in Jutland, Denmark | |
The TM/ETM sensors are equipped with three channels in the visible spectrum (blue, green and red), three channels in the near and mid infrared spectrum where the atmosphere is most translucent, and one channel in the thermal infrared.
Landsat's high spectral resolution has made these sensors very suitable for area classification, and has allowed them to make an important contribution to the development of this field.
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