i Detection of Smoke and Dust Aerosols Using Multi-sensor Satellite ...

3.1 MODIS Instrument
MODIS, one of key sensors of the National Aeronautics and Space Administration
(NASA) Earth Observing System (EOS), was launched onboard the Terra spacecraft on
December 18, 1999 and the Aqua spacecraft on May 4, 2002 (Barnes et al., 2002;
Salomonson et al., 2002). Both Terra and Aqua MODIS are operated in a
sun-synchronous orbit at the altitude of 705 km. Terra descends southwards with the local
equatorial crossing time 10:30 a.m. and Aqua ascends northwards with the local
equatorial crossing time 1:30 p.m. respectively. The MODIS has been widely used for the
study of land, ocean, atmosphere, and solid earth etc. (Justice et al., 1998; Esaias et al.,
1998; King et al., 2003; Parkinson, 2003).
3.1.1 MODIS spectral band
The MODIS makes the Earth observations with 36 bands, covering the wavelength
range from 0.4 to 14.2 μm. The 20 RSBs and 16 TEBs are arranged in four FPAs: VIS,
NIR, Short- and Middle- Wavelength Infrared (SMIR), and Long- Wavelength Infrared
(LWIR), shown in Fig. 3.1 (Che et al., 2005). Three different spatial resolutions are
designed according to the band specifications and science applications: 250 m (band 1-2),
500 m (band 3-7), and 1 km (band 8-36). The number of detectors of each band is 40, 20,
and 10 respectively corresponding to its spatial resolution (Barnes et al., 2002;
Salomonson et al., 2002). The specifications of all spectral bands are listed in Table 3.1.
Among these bands, band 1 (red), band 4 (green), and band 3 (blue) are usually used for
constructing RGB true color image. The MODIS is a cross-track scanning radiometer
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