Suomi National Polar-orbiting Partnership (NPP) Sensor Data Record (SDR) Version 2.0.1 Patch for SDR Version 2.0
20 October 2014The Joint Polar Satellite System (JPSS) project had decided to begin direct broadcast of CrIS Full Spectral Resolution (FSR) data tentatively scheduled for November, 2014. As a result of the increased downlink data rate, VIIRS M-Band 7 and CrIS Field-of-View (FOV) number 4 will no longer be included in the direct broadcast. The CSPP SDR V2.0.1 software patch for CSPP SDR V2.0 is prepared to handle these changes, using the following approach: CrIS SDR
The CrIS version 2.0.1 SDR software includes a truncation algorithm to handle the FSR data that will be included in the Suomi-NPP downlink. When the switch to FSR data occurs, the software will ingest the full resolution data and truncate it, thus creating output files of the same size and format as the current SDRs. The only exception to this is that there will be no observations for FOV 4, which will contain fill values. The truncation will continue until the full spectrum CrIS SDR software is available and has been validated.VIIRS SDR
When S-NPP begins downlink of CrIS FSR data, the extra required bandwidth will come at the expense of the downlink of M-Band 7 (.865 micron). If the CSPP v2.0.1 software detects that the SVM07*.h5 data set contains all fill values, and the SVI02*.h5 data contains valid reflectances, the SVM07 radiance and reflectance values will be reconstructed using those I-Band 2 (SVI02) .865 micron observations. The reconstructed file will contain data values that are close but not identical to what the downlinked values would be. The algorithm used by CSPP SDR 2.0.1 for duplication is very simple; it adds together the appropriate higher spatial resolution SVI02 data pixels and then divides by 4 to create the SVM07 replacement pixel. If any of the 4 SVI02 data values that go into producing one SVM07 pixels is missing, the value is stored in the SVM07 file as missing. Since the M-Band 7 is a dual gain channel, differences in the reconstructed array may be most noticeable in dark (small radiance/reflectance) scenes. Downstream products which include the use of M-Band 7 reflectances will be affected by this as well, including the VIIRS cloud mask product.The CSPP ATMS SDR software is not affected by this change.
Please note: Once the exclusion of VIIRS M-Band 7 and the inclusion of CrIS FSR in the S-NPP direct broadcast begins, CSPP SDR software will fail to produce SDRs without implementing this Patch.