MODAPS PCR 17-009
| PCR Number | 17-009 |
|---|---|
| Date | 2017-04-03 |
| Initiator | Xiaoxiong (Jack) Xiong (MCST) |
| Abstract | PGE02 v6.2.0 (Terra) 1. The crosstalk correction algorithm described in #8 has been implemented in Terra MODIS PGE02 V6.2.0. 2. A penalty to the uncertainty is added to bands 27-30 based on the magnitude of the corrected signal. 3. The detector_quality_flag_value table has been rederived from the start of the mission to better reflect the QA status for detectors in bands 27-30. 4. The semi-reprocessed m1 and RVS LUT from 2012 onwards for Terra MODIS bands 1 and 2 has been integrated into this delivery. |
| Problem Statement | The contamination from electronic crosstalk in Terra MODIS longwave infrared PV bands (27-30) has been steadily increasing over the mission. Its impact on science products, especially the cloud mask product, is becoming significant in recent years. The crosstalk correction in L1B has been requested to support the Collection 6.1 reprocess. |
| Description of Change | 1. A moon-based algorithm developed by MCST is used to identify the signal contamination for each detector in bands 27-30 from the scheduled Moon observations. The contribution to the contamination from all involved detectors can be quantified to derive the time-dependent crosstalk correction coefficients. A linear correction algorithm is implemented in the L1B using the derived coefficients to calculate the signal contamination and make corrections to the on-board calibrator (OBC) data and Earth-view (EV) data. 2. The uncertainty algorithm has to be updated for bands 27-30 to account for the effect of the crosstalk correction. 3. The detector quality can be greatly improved for some detectors in bands 27-30 after applying the crosstalk correction. The QA status also needs to be updated accordingly. 4. The m1 and RVS for bands 1 and 2 are also reprocessed between 2012 and 2016 as per NASA Land Team’s request to improve the temporal stability. |
| Products Affected | Terra MODIS L1B product |
| Software Affected | PGE02 v6.2.0 (Terra) |
| Processing String to Receive the Change | Terra Forward Processing and Terra Reprocessing |
| Downstream Product Effects | All products use Terra MODIS bands 27 - 30, and bands 1 and 2. |
| Data Granules to be Used for Science Testing | Multiple science tests covering the mission and over different geolocations have been performed by the University of Wisconsin and NASA Atmosphere Team. The reprocessed m1/RVS for bands 1 and 2 have also been evaluated by the Land Team. |
| Justification | The feedback from the science testing is very positive. The current crosstalk correction algorithm is very effective in reducing the impact from the crosstalk contamination. The quality of the Terra MODIS cloud mask product can be significantly restored. The reprocessed m1 and RVS for Terra bands 1 and 2 greatly improve the stability of the trending. |
| Effective Date for Implementation of Change | Completed |
| Status | Major algorithm development completed. Xiaoxiong Xiong approved 04/12/2017. Steve Platnick approved 04/04/2017. Sadashiva Devadiga approved on 04/03/2017. Michael King approved 04/14/2017. Gang Ye implemented 04/17/2017. |
