Blackbody Calibration

DOC NOAA NESDIS


Blackbody Calibration



	Correction for GOES Imager Midnight Blackbody Calibration Error
	Description of Problem
	Calibration Correction
	Correction Algorithm
	Slide 5
	Scence Temperature Errors Predicted from Slope Errors vs Time
	Observed Scene Temperature Errors vs Time
	Observed vs Predicted Errors
	Slopes vs Time
	Uncorrected Slopes vs Time
	Corrected Slopes vs Times
	Parallel Test of Midnight Blackkbody Correction (MBCC)
	Slide 13
	Slide 14
	Conclusion

Description of Problem

At certain times of the year, the magnitudes of the computed calibration slopes for the GOES Imagers' infrared channels exhibit anomalous dips during the approximately six hours centered on satellite midnight.
The amplitudes of the dips is greatest for Imager channels at the shortest wavelengths.
For GOES-8, the anomalous dips occurred during the months between April and October. However, GOES-10 experiences this phenomenon all year round. GOES-12, which became operational April 1, 2003, has so far exhibited the effect all the time, but we do not know whether it will continue all year.
Assuming these slope dips are errors, they will cause erroneous decreases in measured scene temperatures. Such decreases appear to have been observed.
The cause of the slope dips is believed to be interference by radiation from solar-heated structural components that reaches the Imagers’ detectors during the blackbody look—see next slide.

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