MODAPS PCR 12-002
| PCR Number | 12-002 |
|---|---|
| Date | 2012-08-20 |
| Initiator | Brian Wenny |
| Abstract | PGE02 v6.1.14 was updated to implement multiple code updates that satisfy the requests of users and NASA requirements. |
| Problem Statement | 1. At the request of science team members, interpolation from nearby good detectors for inoperable detectors at the native resolution is no longer required. A specific fill value should be used in place of interpolation.2. Detectors 29 and 30 of Terra band 2 suffer from a cross-talk problem from another band, which affect only the first of the 4 sub-frames of data in each frame.3. The L1B code is currently written to treat as a fatal error the occurrence of any engineering data packet that indicates that PCLW (Photo Conductive Long Wave infrared) electronics side A and side B are on simultaneously. However the PC subsystem is one of only three on the MODIS instrument where it is in fact possible to have the side A and side B electronics on at the same time. This has never been done, and is unlikely to ever be done. However, corrupt data packets have been known to make it appear as if this was happening, usually for just a few scans.4. At the request of Science Team members, the calculation of the uncertainties was reviewed by MCST analysts. They concluded that the current calculations produce results that are not as accurate as they could be.5. The on-board calibrator may not be able to correctly track the gain change for a few RSB bands, and the RSB rvs derived from the Moon and SD calibrations may not be able to correctly reveal the rvs on-orbit change either.6. NASA requires that all NASA data files shall have Digital Object Identifier (DOI) metadata. |
| Description of Change | 1. The interpolation for inoperable detectors at the native resolution is no longer applied.2. Provide new LUTs containing sub-frame bit flags for every detector in 250m and 500m bands indicating whether they are noisy or dead. Change the L1B code to mark pixels affected by inoperable sub-frames with a special fill value. Provide Metadata in the L1B product identifying which sub-frames are noisy and inoperable.3. Change the algorithm so that a granule will not be dropped due to both sides of PCLW electronics being on at the same time, unless this is true for all scans in the granule. For those scans where both sides of PCLW electronics are on at the same time, no calibration will be performed, and the pixels will be filled by a special value 65524 for the L1B Scaled Integer (SI) output.4. New algorithms have been developed for estimating the uncertainties, requiring corresponding changes in the LUTs.5. Change to model the RSB rvs with a 4th order polynomial instead of quadratic one, as a function of frame number. The dimension size of RSB rvs LUT has to be changed to accommodate the 4th polynomial coefficients.6. Two metadata attributes named “identifier_product_doi” and “identifier_product_doi_authority” should be added to each L1B data product with their corresponding attribute values. |
| Products Affected | MYD021KM, MYD02HKM, MYD02QKM, MYD021QA1. The L1B product at native resolution from inoperable detectors.2. A special fill value has been introduced for the pixels in L1B granule affected by in-operable sub-frames.3. A special fill value has been introduced to mark pixels filled because both sides of the PCLW electronics are turned on.4. The Uncertainty Indices SDSs in the L1B product5. The L1B product for RSB bands.6. New core metadata and global attributes can be used to identify L1B data product. |
| Software Affected | PGE02 v6.1.14Process: MOD_PR02 |
| Processing String to Receive the Change | Terra Forward, Terra Reprocessing |
| Downstream Product Effects | 1. All downstream products will see fill values at native resolution rather than the interpolated data, for any inoperable detectors.2. All downstream products using the bands 1-7 will see fill values rather than bad data, for any inoperable sub-frame.3. All downstream products will have entire granules of data available (that would otherwise not have been) if corrupt data packets make it appear that both sides of PCLW electronics were on for a few scans.4. Any downstream product using the L1B Uncertainty Indices will see somewhat more accurate values.5. Any downstream product using L1B reflectance and radiance product in RSB bands will see less spurious variation due to scan angle.6. None. |
| Data Granules to be Used for Science Testing | TBD. |
| Justification | 1. Inoperable detectors cannot produce reliable calibration data, and should be dropped.2. Inoperable sub-frames cannot produce reliable calibration data, and should be dropped.3. While calibration data are not reliable for the scans with both sides of electronics on, this should not cause the entire granule to be dropped. This is especially true since most such events are spurious, due to corrupt data packets.4. At the request of the users, a thorough re-analysis of the uncertainty indices was done, new algorithms were developed, and preliminary results were reported at the MsWG meeting, where they met the approval of the science teams.5. The higher-order polynomial more accurately fits the available calibration data, and preliminary feedback from the science teams has been positive.6. The change enables the internet service with unique and persistent identifiers in each L1B data product. |
| Effective Date for Implementation of Change | TBD |
| Status | Steve Platnick approved for Atmospheres, Sadashiva Devadiga approved for Land, Bryan Franz approved for Oceans and Michael King approved on 11/12/2012. |
