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Level 1B
Instrument Performance History

TEB PC Bands 33, 35, 36 Saturation Problem
AQUA

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

DESCRIPTION:

The MODIS instrument on-board calibrator Blackbody (OBC BB) operates warm-up and cool-down cycle occasionally from 270K (about the on-orbit ambient) to 315K for the thermal emissive bands (TEB) on-orbit calibration and characterization. Aqua MODIS pre-launch calibration results indicate that three of the PC bands (B33, 35, and 36) saturate at temperatures below 310K.

IMPACT TO L1B DATA SET:

Preliminary Science Team examination of the data sees no impact on the L1B products due to this saturation characteristic.

ESTIMATED IMPACT TO L2 SCIENCE PRODUCTS:

Negligible.

CAUSE OF EFFECT:

Aqua MODIS pre-launch calibration results indicate that three of the PC bands (B33, 35, and 36) saturate at temperatures below 310K. Because TEB detectors are calibrated each scan using the BB, the original calibration algorithm used for Terra MODIS TEB can not provide the correct calibration coefficients (b1) for these three bands when they are saturated when viewing the OBC BB.

MITIGATION APPROACH/ADDED TESTING TO CHARACTERIZE EFFECT:

A new algorithm has been designed and implemented in the Aqua MODIS L1B code for data processing. The Aqua-specific algorithm that computes the correct calibration coefficients (b1) for these three bands when they are saturated while viewing the OBC BB has been implemented from the beginning of the mission. The algorithm uses fixed coefficients stored in a LUT if the BB temperatures exceed the bands' saturation temperatures, which are stored in another LUT. The saturation temperatures and pre-determined coefficients in the LUTs are monitored every warm-up and cool-down cycle, and updated when necessary.

ESTIMATED SCHEDULE TO COMPLETE:

Finished.

HISTORY OF CHARACTERISTIC:

Life of mission.

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