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MCST Calibration Information
MODIS On-Board Calibration Sources
MODIS has a full complement of On-Board Calibrators (OBCs) that generate various stimuli to provide radiometric, spectral and spatial calibration of the MODIS instrument. We identify the four OBCs as the
Blackbody (BB),
Solar
Diffuser (SD),
Solar
Diffuser Stability Monitor (SDSM), 
and
the
Spectroradiometric
Calibration Assembly (SRCA)
.
The BB is the prime calibration source for the thermal bands located from 3.5 µm to 14.4 µm, while the SD provides a diffuse, solar-illuminated calibration source or the visible, near infrared, and shortwave infrared bands (0.4 µm < = lambda < 2.2 µm). The SDSM tracks changes in the reflectance of the SD via reference to the sun so that potential instrument changes are not incorrectly attributed to changes in this calibration source.
The SRCA is a very complex, multifunction calibration instrument that provides in-flight spectral, radiometric and spatial calibration.
MODIS External Calibration Sources
Two additional calibration techniques that MODIS uses are views of the moon and deep space. The advantage of "looking" at the moon is that it enables MODIS to view an object that is roughly the same brightness as the Earth. Like the on-board Solar Diffuser, the moon is illuminated by the sun; however, unlike the Solar Diffuser or the Earth, the moon is not expected to change over the lifetime of the MODIS mission. "Looking" at the moon provides a second method for tracking degradation of the Solar Diffuser.
"Looking" at deep space provides a photon input signal of zero, which will be used as an additional point of reference for calibration. (Stars are too dim to be "seen" by MODIS.)
Calibration Information Types
Current Status
During the May 6, 2003 (data day 126/2003) Terra Solar Diffuser calibration with the Solar Diffuser screen unexpectedly did not open during this calibration although the drive motor moved through the entire range of the screen from closed to open to closed.
Aqua calibrations are proceeding normally.
Responsible Civil Servant:
Dr. Jack Xiong <Xiaoxiong.Xiong.1@gsfc.nasa.gov>
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Last Update: Tuesday, May 6, 2008 10:32 AM