Monitoring Drought Using Coarse-Resolution Polar-Orbiting Satellite Data - Monitoring and Predicting Agricultural Drought: A Global Study - page 58

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Figure 5.1 The electromagnetic spectrum [from Lillesand and Keifer, 2000].

pa ssive microwave. Chapters 7 and 8 describe applications of passive and
ac tive microwave remote sensing to drought monitoring, respectively.

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Some Remote Sensing Systems for Monitoring Drought

La ndsat

Early use of satellite data was pioneered by the Landsat series originally
known as the Earth Resource Technology Satellite (ERTS; http://landsat7.
usgs.gov/index.php). Landsat was the first satellite specifically designed for
broad-scale observation of the earth's land surface. A series of Landsat
satellites (Landsats 1-5 and 7; 6 failed at launch) have provided visible
and near-infrared data since 1972, with additional bands in the shortwave
infrared and thermal regions for Landsat 4, 5, and 7. The Landsat satellites
orbit the earth in sun-synchronous mode with a repeat cycle over any given
location of 16 days. The earlier Landsat satellites provided imagery with a
multispectral scanning instrument (MSS) at a resolution or pixel size of 80
m. Landsats 4 and 5 carried an additional sensor known as the thematic
mapper (TM) that provided image data at a 30-m resolution over the
visible, near-, and shortwave-infrared wavelengths with a 120-m thermal
band. Currently, Landsat 7 carries an enhanced thematic mapper (ETM

[58],

)
sensor that provides improved radiometric calibration, a panchromatic
band at 15 m, visible through shortwave infrared bands at 30 m, and a
thermal band at 60 m spatial resolution.

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SPOT

The Systeme Probatoire pour l'Observation de la Terre (SPOT) satellite
sensor series ( http://www.spotimage.fr/home/), developed by Center Na-
tional d'Etudes Spatiales (CNES) in France, was first launched in 1986 and
provides data at a spatial resolution of 10 m (panchromatic mode) and 20
m (multispectral mode) using what is known as the high-resolution visible