Geography Reference
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(ETM) sensor and failed on launch, and LANDSAT-7, with its Enhanced The-
matic Mapper Plus (ETM+) sensor. LANDSAT-7 also had a 378 gigabit Solid
State Recorder (SSR) that could store 42 min (about 100 scenes) of sensor data
and 29 h of housekeeping telemetry concurrently (L-7 Science Data User's
Handbook). No MSS-sensors were included on either satellite (Fig.
4.2
).
4.1.2 TERRA-ASTER
In 1999, after the cooperation between NASA and the Japan's Ministry of
Economy Trade and Industry (METI), the Advanced Space-borne Thermal
Emission and reflection Radiometer (ASTER) was launched into the space. It was
held on board the NASA-TERRA satellite. The ASTER-sensor represents the next
generation in remote sensing, following the older LANDSAT-TM. It acquires high
spatial resolution data in 14 spectral bands, ranging from visible to thermal
infrared portions. This sensor contains three separate instrument subsystems that
operate in different spectral portions and have their own telescope(s). The sub-
systems are: (1) the Visible and Near Infra-Red (VNIR): operates within three
spectral bands at visible and NIR wavelengths of 0.52-0.86 lm, with a spatial
resolution of 15 m. It is especially useful for topographic interpretation because of
its along-track stereo coverage with 15 m spatial resolution. Also, it is useful in
assessing vegetation and iron-oxide minerals in surface soils and rocks; (2) the
Short-Wave Infra-Red (SWIR): operates within six spectral bands in the NIR
region of 1.600-2.430 lm, through a single-nadir pointing telescope that offers a
spatial resolution of 30 m. These six bands were selected mainly for the purpose of
surface soil and mineral mapping; and (3) the Thermal Infra-Red (TIR): operates
within five bands inside the thermal infrared region of 8.125-11.65 lm, using a
single, fixed-position, and nadir looking telescope with a spatial resolution of
90 m. This subsystem allows for a more accurate determination of the variable
spectral emissivity of the land surface, and hence a more accurate determination of
the land surface temperature. The spatial coverage of the ASTER-sensor is at
60 9 60 km (Fujisada
1995
; Yamaguchi et al.
1998
).
The relatively high spatial (Fig.
4.1
) and spectral (Fig.
4.3
) resolution of the
ASTER-data in comparison to LANDSAT-data can increase the ability of sepa-
ration between the various ground surface features and decrease the problems of
mixed pixels (Yamaguchi et al.
1998
). Therefore, ASTER-data are more suitable
for LULC-classification (Bagan et al.
2008
).
The ASTER-sensor, because it is the only high spatial resolution sensor, is the
''zoom lens'' for the other carried sensors onboard the TERRA-satellite. TERRA is
in a sun-synchronous orbit, 30 min behind LANDSAT-ETM+, and it crosses the
equator at about 10:30 am local solar time. ASTER can obtain data over the whole
globe with an average obligation cycle of 8 % for each track. This offers a gaining
of about 650 scenes per day (subject to on-board storage limitations), that are
processed to the two products types (Level-1A; of these, about 150 are processed
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