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Level 1B
Instrument Performance History

Incomplete calibration for Band 21

Description | L1B Impact | L2 Impact | Cause | Mitigation | Schedule | History

DESCRIPTION:

Band 21 calibration is imprecise at high temperatures.

IMPACT TO L1B DATA SET:

This effect causes increased uncertainty in the brightness temperature due to the indirect nature of the calibration. Detector to detector striping exists, but is within specifications.

ESTIMATED IMPACT TO L2 SCIENCE PRODUCTS:

Science research will be seriously impacted until the calibration can be extended.

CAUSE OF EFFECT:

The saturation brightness temperature for this fire detection band is specified at 500 K. Pre-launch test targets had a maximum brightness temperature of 340 K, which equals about 3.5% of full radiance scale. Band 21 is expected exhibit the non-linear characteristics seen in other MWIR bands, but the calibrated temperature range is not adequate for determining non-linear calibration characteristics for this band.

MITIGATION APPROACH/ADDED TESTING TO CHARACTERIZE EFFECT:

The linear gain coefficient for this band is computed nearly monthly using an elevated temperature cycle of the OBC-BB. LUTS are updated as needed.
Early studies indicated that the calibration might be tested with observations of the moon. Literature values suggest the moon has a brightness temperature of about 400 K at 4 µm. To date, the variability in the MWIR observations of lunar radiance is too great to allow for this calibration.

ESTIMATED SCHEDULE TO COMPLETE:

TBD. Gains are updated as needed.

HISTORY OF CHARACTERISTIC:

Description | L1B Impact | L2 Impact | Cause | Mitigation | Schedule | History

Please contact Jack Xiong with any technical questions concerning these pages.

Responsible Civil Servant: 
Dr. Jack Xiong <Xiaoxiong.Xiong.1@gsfc.nasa.gov>

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Last Update:  July 3, 2008