MODAPS PCR 17-002
| PCR Number | 17-002 |
|---|---|
| Date | 2017-05-01 |
| Initiator | Sudipta Sarkar |
| Abstract | PGE25 6.0.31 Update version of MOD_SS. PGE35 6.0.22 Update version of MOD_SS. |
| Problem Statement | Some of the 16-day composite VI retrievals in the operational processing contain contradicting state values for quality indicators in quality bits representing the "Pixel Reliability" and "MODLand Quality" |
| Description of Change | On rare occasions pixel level quality flags for the retrieved VI indicate good quality state in the "MODLand Quality" and at the same time as poor reliability or no retrieval in the "pixel reliability" bits. In case of PGE25 (250/500m resolution product) it was traced to error in check and propagation of the MODLand quality flag from the upstream and was fixed by evaluating the flag state within the VI process. In the 1km resolution product (PGE35), for some pixels though there was no retrieval "MODLand Quality" Flag and the "Pixel Reliability" flag seems to indicate valid retrievals. This was fixed by forcing the quality flag to the correct value by verification of the retrieved science parameters. PGE25 was updated to generate new *ornl_* subsets and PGE35 was updated to stop old fn_subset generation. |
| Products Affected | MOD13A1, MOD13A2, MOD13Q1, MYD13A1, MYD13A2, MYD13Q1 |
| Software Affected | PGE25 6.0.31, PGE35 6.0.22 |
| Processing String to Receive the Change | Terra and Aqua Forward Processing. |
| Downstream Product Effects | None. |
| Data Granules to be Used for Science Testing | Ran science test generating global product from a 16-day period of Aqua and Terra. |
| Justification | Retrievals with contradicting QA flags in the QA datasets can't be reliably used in applications. However, review of the operational product indicated only a very small fraction of global retrievals are affected by this software bug. The revised PGE will be only be used in the forward processing. A separate tool will be developed and used to fix the QA dataset in the affected files. No re-reprocessing is required. |
| Effective Date for Implementation of Change | Completed. |
| Status | Major algorithm development completed. Sadashiva Devadiga approved on 01/05/2017. Michael King approved 01/06/2017. Gang Ye implemented 01/09/2017. |
