CSPP SDR V2.0.1 Patch for CrIS and VIIRS in preparation for S-NPP Downlink changes
The JPSS project will start transmitting the Suomi-NPP CrIS Instrument Full Spectral Resolution (FSR) data scheduled to begin in mid-November. As a result of the increased bandwidth required to downlink the FSR data, VIIRS M-Band 7 and CrIS Field-Of-View (FOV) number 4 will no longer be included in the direct broadcast. A CSPP SDR V2.0.1 patch has been created to handle these changes, taking the following approach:
CrIS SDR
The CrIS version 2.0.1 SDR patch 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 patch 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.
ATMS SDR
The ATMS data downlink and CSPP ATMS SDR software is not affected by this change.
Please note: Once the switch to CrIS FSR occurs, older versions of CSPP SDR software (for example, Version 1.5) will fail to produce CrIS and VIIRS SDRs. Upgrading to a patched version of CSPP SDR 2.0 will be required.
In addition, there may be unanticipated consequences of the FSR downlink on the SDR software. We will be monitoring the direct broadcast data very closely and provide updates if they are required as quickly as possible.
The CSPP V2.0 SDR software and the V2.0.1 Patch are available for download from the CSPP website:
http://cimss.ssec.wisc.edu/cspp/
Please feel free to contact us with any questions or concerns you may have. Please use the 'Contact Us' form from our website to submit any questions or comments about CSPP.
Kathy