MODAPS PCR 16-008

PCR Number 16-008
Date 2016-04-05
Initiator Bill Ridgway
Abstract PGE03 v5.3.15 -- Added thresholds.dat.terra.v13nrt and destripe_config_terra.dat.v5nrt for nrt. Matched with the logic used by C6 for chosing destripe_config file.

PGE03 v6.0.47 -- Use destripe_config_terra.dat.v5nrt in NRT.

PGE06 v51.0.18 -- Added destripe_config_terra.dat.v5nrt for nrt. Matched with the logic used by C6 for chosing destripe_config file.

PGE06 v6.0.91 -- Use destripe_config_terra.dat.v5nrt in NRT.

Problem Statement Recovery from the Feb 19, 2016 safe-hold resulted in degraded radiances in Terra Bands 27 & 29 (both bad and noisy detectors). Cloud mask, atmospheric profiles and some downstream products were seriously impacted by bad radiances in these thermal bands.
Description of Change Updated PGE03 threshold tests for these bands. Two cloud detection tests (8.6-11 micron BTD and 6.7 micron BT) in the Terra MODIS cloud mask algorithm have been effectively eliminated by modifying the test thresholds. The new thresholds are set in such a way as to prevent the corresponding tests from reporting any cloud, whether or not clouds actually exist in the scene, i.e., 1-km MODIS pixel. The 6.7 micron BT thresholds are set to non-physically low values, while the 8.6-11 micron BTD thresholds are made unreasonably high. This change restores cloud mask quality to near pre-safe-hold levels.

Updated the de-striper that previously used Band 27 Detector 9 as a reference. This detector is no longer in family and is vulnerable to producing negative radiances (reason not yet clear). The de-striper has replaced detector 9 with detector 4 as the reference. This changes minimizes striping in the profile product.

Products Affected PGE03 products MOD35_L2 and MOD07_L2 and downstream products
Software Affected PGE03 v5.3.15, PGE03 v6.0.47, PGE06 v51.0.18, PGE06 v6.0.91
Processing String to Receive the Change Terra Forward, Terra Reprocessing
Downstream Product Effects None
Data Granules to be Used for Science Testing Science Testing Required: Single day science tests were run for Terra 2016 Day 061. See AS 1393/1399.
Justification Avoids unacceptable level of false positives in cloud detection, particularly over ocean. Avoids striping and bad average values in profile products.
Effective Date for Implementation of Change ASAP Terra forward processing starting at 2016 day 059 or thereafter.
Status Major algorithm development completed. Steve Platnick approved 04/06/2016; Sadashiva Devadiga approved 04/06/2016. Gang Ye approved on 04/07/2016.