Biology Reference
In-Depth Information
3.3.1 Satellites, Sensors, Measurements, and Data Products
There are two types of remote sensing instruments: passive and active sen-
sors. Passive sensors measure the radiance reflected by or emitted from the
Earth's surface at different wavelength bands, depending on the nature of the
geophysical parameters to be measured. Active sensors, on the other hand,
measure ground reflected radiation originally emitted from the sensors.
Radar and LIDAR are two common types of active sensors. In the following
sections, we describe a few of the passive sensors currently being flown that
can measure some of the climatic and environmental factors pertaining to
the diseases described earlier in this chapter.
3.3.1.1 Landsat
The Landsat series (USGS 2009a) began in 1972 with the first Landsat 1 mis-
sion, followed by several others: Landsat 2, Landsat 3, Landsat 4, Landsat
5, and the most recent Landsat 7, which was launched in April 1999. Both
Landsat 5 and Landsat 7 are still collecting data. Landsat 5 was launched
in 1994 and carries the multispectral scanner (MSS) with four spectral
bands ranging from visible to near infrared with a ground resolution of
57 m × 79 m. Landsat 5 also carries a Thematic Mapper (TM), which con-
sists of an array of seven spectral bands from the visible to mid-infrared
(30 m) and a thermal band (120 m). Landsat 7 carries an Enhanced Thematic
Mapper Plus (ETM+) with eight spectral bands, including the visible to the
mid-infrared with a spatial resolution of 30 m, a thermal band with 60 m
spatial resolution, and a panchromatic band with a spatial resolution of
15 m. Landsat missions provide several land products, including radiomet-
rically and geometrically corrected, and terrain-corrected data. Through
ground cover classification techniques, Landsat data can be used for iden-
tifying potential larval habitats of large dimension and certain contextual
determinants.
3.3.1.2 Advanced Very High Resolution Radiometer (AVHRR)
The Advanced Very High Resolution Radiometer (AVHRR) (Applied
Physics Laboratory 2009) is carried onboard the National Oceanic and
Atmospheric Administration (NOAA) Polar Orbiting Satellites (POES).
It collects global daily information about the land, ocean, and the atmo-
sphere. The first AVHRR sensor was launched in October 1978 onboard the
TIROS-N satellite, and the two sensors onboard the most recent NOAA-12
and NOAA-14 missions are still collecting data. A typical AVHRR sensor
has five bands ranging from visible and mid-infrared to thermal bands.
Among AVHRR data products are vegetation indices and logs of sea sur-
face temperature.
