Environmental Engineering Reference
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Fig. 3.3 Variation in detector response for the Terra MODIS (days since launch) for the angle of
incidence ( AOI ) relative to the solar diffuser (SD—AOI
50.2 ) and when looking at the moon
¼
11.2 ), showing the mirror side 1 ( MS-1 ) example. Similar changes have occurred for the
Aqua MODIS
(AOI
¼
lifetime of the instruments up through 2011. An exception is the registration of the
cold focal plane bands relative to the warm focal plane bands for the Aqua MODIS
instrument by 0.2-0.35 km. That this aspect did not meet specifications was known
prior to launch, but approval to go back in and fix this problem was not approved
due to budgetary considerations. The offset has remained constant during the
operation of both instruments. In the vast majority of instances, this exception has
not created insurmountable problems in the research accomplished using the
MODIS data.
The calibration consistency of the MODIS instruments can also be validated
using carefully selected “ground-truth sites” that are uniform and stable in their
characteristics over time or for which there are good, independent data
corroborating the MODIS observations. One area that has been used is located on
the Antarctic Plateau and is called the Dome Concordia (“Dome C”) site at 75.102
south and 12.395 east (see Wenny and Xiong 2008 ). Other sites include one in the
Libyan Desert and selected deep convective clouds (see Doelling et al. 2011 ). An
example is shown in Fig. 3.5 for surface temperature (band 31—see Table 3.1 )
observed over the Dome C site. The mean difference between the Aqua and Terra
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