MODAPS PCR 21-012
| PCR Number | 21-012 |
|---|---|
| Date | 2021-03-09 |
| Initiator | Jim Ray |
| Abstract | PGE199 1.0.11 -- 1) Added sanity checks for geolocation data when determining lat/lon extent of data in a granule (routine NO_EPH_prescan() in navigate.c) and when interpolating the lat/lon data read from the AVHRR file itself (routine interpol_noaa_geom() in file calib_data.c). 2) Updated PGEVER to '1.0.11' in PGE199/GAPS/src/gaps_HDF.c and postprocessing programs. |
| Problem Statement | AVHRR GAC files with bad geolocation data result in missing orbits from products of PGE199 for that day. |
| Description of Change | A new version of PGE199 (V1.0.11) was delivered, which handles bad geolocation better. |
| Products Affected | AVHRR Version 5 LTDR products. |
| Software Affected | PGE199 1.0.11 |
| Processing String to Receive the Change | MetOp-B Reprocessing. MetOP-B Forward Processing. |
| Downstream Product Effects | Given the rarity of bad geolocation data in the GAC record, there is improvement of only a small number of outputs. The changes in v1.0.11 do not affect data without geolocation errors. |
| Data Granules to be Used for Science Testing | No science test was deemed necessary, given the rarity of the issue. But the changes were confirmed through unit tests conducted by the science team and MODAPS STIG. |
| Justification | This change will eliminate geolocation-based run-time errors in PGE199 processing. Note that these geolocation-based errors were found only in MetOP-B processing, because other satellites are using geolocation derived from ephemeris data, and only processing of the MetOP series uses geolocation internal to the AVHRR GAC file - which, in this case, had errors. |
| Effective Date for Implementation of Change | This PGE199 V1.0.11 will be used in the leading edge of MetOp-B V5 forward processing in AS 465. |
| Status | Major algorithm development completed. Sadashiva Devadiga approved on 3/12/2021. Gang Ye approved on 3/12/2021. |
