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Time-dependent List of Non-Functional or Noisy Detector

Description

Prior to the Aqua MODIS launch, Band 6 exhibited several anomalous detectors. Band 6 performance degraded seriously after launch and presently a majority of the Band 6 detectors are non-functional. Averaging across dead detectors is not possible for regions on the Band where several adjacent detectors are non-functional. One band 5 and several band 6 detectors are non-functional throughout the mission. RSB detectors are declared "noisy" based on the detector-dependent SNR. TEB detectors are declared "noisy" if the detector’s NEdT exceeds the specification for 2 weeks. These conditions are tracked by the Detector Quality Flags (DQF) in the Quality Assurance (QA) LUT.

Impact to L1B Data Set

Non-functional and noisy detectors are flagged to alert users. The L1B code does not calibrate EV pixels for Non-functional detectors. Early in the development of the L1B algorithm, the decision was made to fill the pixels for inoperable detectors with interpolated values from adjacent good detectors. This practice continued through Collection 5. Downstream product users are often unaware that the image data contains interpolated values unless they check the QA product files. As a result, the interpolated values are often treated as actual retrieved values from the sensor. At the request of the science team, Collection 6 will not fill the pixels of inoperable detectors using interpolation. Instead an explicit fill value will be inserted for all inoperable detector scans. This will result in image stripes and be readily apparent to users that the detector is non-functioning.

Estimated Impact to L2 Science Products

The L1B product handles non-functional detectors in a manner to facilitate building images with L1B production data using simple raster scan software for the image generation. Science users should read and use the non-functional detector flags and decide for themselves the optimum manner to handle non-functional detector "gaps" for their products.

Cause of Effect

Band 5 has one delaminated detector and band 6 has several delaminated detectors. Thermal cycling tends to increase delamination.

Mitigation Approach/ Added Testing to Characterize Effect

Data for non-functional detectors have been replaced by nearest live detector averages. Non-functional detectors will be treated differently in Collection 6 processing (starting approximately summer 2009). At that time, non-functional detectors will be given fill values that indicate the status of those detectors.

Estimated Schedule to Complete

Ongoing. MCST continues the monitor the status of each MODIS detectors and corresponding changes in the QA LUT

History of Characteristic

Aqua Collection 6 (V6) processing began in January 2012.  For the remainder of 2012 and much of 2013, concurrent collection 5 and collection 6 processing is ongoing.  The current Aqua MODIS Collection 5 and collection 6 QA LUT update history, a time-dependent list of non-functional, noisy, and out-of-family detectors, is available by clicking on the eponymous links below.  Information for processing based on an earlier version of the L1B code (V4 = version 4) is also available below.