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Level 1B
Instrument Performance History

Thermal leak (Bands 5, 6, 7 and 26)

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

DESCRIPTION:

Energy near 5.3 µm contributes to the SWIR bands (Bands 5, 6, 7 and 26)

IMPACT TO L1B DATA SET:

Affects the calibration accuracy due to the scene dependence of the thermal leak.

ESTIMATED IMPACT TO L2 SCIENCE PRODUCTS:

Affects the calibration accuracy due to the scene dependence of the thermal leak.

CAUSE OF EFFECT:

The spectral out-of-band blocking filters were not designed to cover the complete long-wavelength sensitivity for the SW/MWIR focal plane. The consequence for MODIS Terra is that the SWIR bands are sensitive to thermal signals extending out to near 5.3 µm. Calibration had been performed with the Solar Diffuser using a constant scene brightness.

MITIGATION APPROACH/ADDED TESTING TO CHARACTERIZE EFFECT:

The correction for this effect is based on the use of measurements for MODIS in Band 28, because the spectral weighting function of that band is closest in most geophysical conditions to the contributions from energy near 5.3 µm. The use of Band 28 as a proxy for 5.3 µm energy breaks down in the presence of very low atmospheric precipitable water (where the Band 28 signal receives energy directly from the surface). When this condition occurs over a hot surface (desert) the present algorithm provides too large a correction. When this condition occurs over a cold surface (arctic fields) the correction remains good.

ESTIMATED SCHEDULE TO COMPLETE:

Completed. The correction was turned "on" again with the September 2001 LUT delivery version 3.0.0.6. This LUT will be applied to the new side A daa acquired from July 2, 2001 and beyond.

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