MODAPS PCR 22-017
| PCR Number | 22-017 |
|---|---|
| Date | 2022-12-15 |
| Initiator | Guoqing (Gary) Lin |
| Abstract | PGE01 6.1.8 The "orbit_tolerance" upper limit is changed from 3000.0 to 3000000000.0 in geolocation LUT and the "Validate Orbit Numbers" setting is changed from "TRUE" to "FALSE" in the pcf file in the Terra MODIS geolocation data product generation software. |
| Problem Statement | After Terra constellation exit maneuvers in October 2022, the orbit altitude was lowered about 5 km and the orbit period was shortened about 7 seconds. This orbit change triggered the "orbit_tolerance" upper limit set forth in the geolocation parameter look-up table (LUT) to be violated resulting in geolocation process to fail without generating the L1 geolocation data products after mission DOY 2022-335 (2022-12-01) 03:15:00 UTC. |
| Description of Change | Relax the "orbit_tolerance" upper limit relaxed from 3000.0 to 3000000000.0 in geolocation LUT and change the "Validate Orbit Numbers" setting from "TRUE" to "FALSE" in the pcf file in the Terra MODIS geolocation data product generation software |
| Products Affected | L1 Geolocation products (MxD03, MxD03CP) and all downstream. |
| Software Affected | PGE01 6.1.8 |
| Processing String to Receive the Change | Terra and Aqua Forward Processing. NRT |
| Downstream Product Effects | All C61 Terra and Aqua geolocation products in forward production, starting from December 16th, 2022. For Terra, the same PGE was used to start the stalled Terra processing from December 2, 2022 |
| Data Granules to be Used for Science Testing | A science test was run on data-day 2022 335. Results from Control Point PGE that uses geolocation and L1B data products show that geolocation errors have nominal patterns in the 24 hours of the day and in the scan angles. The errors are around 0 and within +/- 200 around nadir. |
| Justification | The changes enables the geolocation and downstream data products generation that were put on hold since 2022-12-01. |
| Effective Date for Implementation of Change | The revised PGE01 V6.1.8 will be put in the leading edge of C61 forward production on 12/15/2022 and will also be used to process the stalled Terra days from 12/02/2022 onwards. |
| Status | Major algorithm development completed. Sadashiva Devadiga approved on 12/18/2022. Sudipta Sarkar approved on 12/15/2022. |
