Agriculture Reference
In-Depth Information
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(HRV) sensor. The HRV instruments have been in service on SPOT 1, 2,
and 3. Although the SPOT HRV repeat cycle of 26 days is longer and has
only 3 spectral bands as opposed to 7 on Landsat TM and ETM
, the spa-
tial resolution is an improvement, and the SPOT sensors can also acquire
stereoscopic pairs of images for a given location, which is useful in topo-
graphic mapping. SPOT 4 was launched in May 1998 with an additional
sensor named VEGETATION (VGT), designed specifically to monitor land
surface parameters on a global basis at 1 km spatial resolution. VGT mon-
itors vegetation dynamics on a daily basis and globally in four spectral
bands, from visible to shortwave infrared.
+
N
OAA-AVHRR
[59],
The advanced very high resolution radiometer (AVHRR) instrument on
board the NOAA series of satellites
(http://www.nesdis.noaa.gov/)
has pro-
vided daily data on the global environment for the last 20 years. Although
the NOAA series of satellites was designed for weather and climate obser-
vations, its broad bands in the visible through thermal-infrared portions
of the spectrum have been used effectively for large-scale monitoring of
vegetation dynamics, especially in arid and semiarid areas (Tucker et al.,
1983; Justice, 1986). Since 1981, the compilation of vegetation measure-
ments from NOAA-7, -9, -11, -14, and currently NOAA-16 has provided
a continuous stream of high temporal resolution data. Although the nom-
inal spatial resolution for NOAA data is 1 km, satellite storage limitations
enforced degrading of 1-km data to 4-km data to achieve global coverage
on a daily basis. Data at about 1 km resolution can only be gathered if
there is a local receiving station when the satellite passes overhead.
Line
——
1.6
——
Norm
PgEn
[59],
IRS
The Indian Space Research Organization (ISRO;
http://www.isro.org/
programmes.htm)
currently has several satellites under the Indian Remote
Sensing Satellite (IRS) system for natural resource monitoring and man-
agement. These data are distributed by ANTRIX Corporation Ltd., the
commercial arm of the ISRO, and also by Space Imaging Corporation
in the United States. The IRS-1C and IRS-1D satellites together provide
continuous global coverage with many advanced capabilities. The IRS-P5
and IRS-P6 offer a very high-resolution panchromatic camera for carto-
graphic applications as well as specific capabilities for agricultural appli-
cations.
M
ODIS
One of the most advanced remote sensing systems for land surface stud-
ies is NASA's Moderate Resolution Imaging Spectroradiometer (MODIS;
http://modis.gsfc.nasa.gov/)
sensor on board the Earth Observing System
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