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

operated in the A-train orbit with similar local equatorial crossing time. To fully take
advantages of multi-sensor system, these two sensors, MODIS and CALIPSO, are
combined together for Asian dust detection.
5.1 CALIPSO Instrument and Measurements
CALIOP is a lidar (LIght Detection And Ranging) sensor, namely a laser radar,
providing information on the vertical distribution of aerosols and cloud as well as their
optical and physical properties (Winker et al., 2003). Current remote sensing capabilities
can be enhanced by the CALIPSO by providing global, vertically-resolved measurements
of aerosol distribution. Cloud and aerosol layers can be discriminated easily using the
magnitude and spectral variation of the lidar backscatter (Liu et al., 2004).
5.1.1 CALIPSO instrument
The CALIPSO mission was launched on April 28, 2006. It is flying at the same orbit
as Aqua spacecraft with 1 minute and 15 seconds behind. The CALIPSO payload consists
of three instruments: a two-wavelength, polarization-sensitive lidar (CALIOP), the Image
Infrared Radiometer (IIR) and the Wide Field Camera (WFC) (Winker et al., 2003). The
CALIPO is a two-wavelength polarization-sensitive lidar. It is designed to acquire the
vertical profiles of aerosols with backscatter signal at 532 nm and 1064 nm in both
daytime and nighttime, as well as profiles of linear depolarization at 532 nm. The IIR
with three channels in the infrared window region is optimized for retrievals of cirrus
particle size. The WFC has one visible channel that provides meteorological context and
a means to accurately register CALIPSO observations to those from MODIS on the Aqua
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