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Channel to channel non-uniform response functions within a band

Description

This effect appears in the MWIR thermal bands (Bands 20 - 25). It is seen as along track striping within a scene. [VERIFY: It appears less prominently in the LWIR PV bands (27 – 30)]

Illustration of effect

Band 21 MODIS scene shows striping without crosstalk correction

Band 21 MODIS scene shows striping without crosstalk correction

Band 21 MODIS scene shows less striping with crosstalk correction applied

Band 21 MODIS scene shows less striping with crosstalk correction applied

Impact to L1B Data Set

Non-uniform channel to channel response of 0.5% to 1.0% in radiance has been reported.

Estimated Impact to L2 Science Products

The effect could introduce errors or uncertainties of up of 2 degrees Celsius in a 4-µm based Sea-Surface Temperature product.

Cause of Effect

The effect is due to the use of a linear calibration for these bands in the initial version of the algorithm, when the actual functioning of the detectors is non-linear (quadratic). Slight variations in the non-linear behavior of one detector to another will lead to an apparent striping in the radiance product for temperatures different than the temperature of the OBC-BB.

This situation is the result of the pre-launch electronics change for electronic cross-talk.

Mitigation Approach/Added Testing to Characterize Effect

On-orbit observations of an OBC-BB over the temperature range 274 K to 315 K enabled a determination of these non-linear terms, and these values were installed with the LUT update known as the St. Patrick’s Day update, beginning on 17 March 2000.

Estimated Schedule to Complete

Completed.

History of Characteristic

Epoch NumberTime SpanVersion Number at start of epochGeneral CharacteristicsImprovementsDocumentation
1Feb. 24, 2000 - March 16, 2000 2000055.1550 - 2000076.21222.3.2.0Imprecise calibration due to use of pre-launch gains.  
2March 16, 2000 - present 2000076.2122 - present2.3.2.3 Updated gains from on-orbit study fixes the problem.MCST library document M0973