VIIRS ellipsoid and terrain-corrected geolocation files

[wbresky]

I have been using the VIIRS ellipsoid geolocation files available at NOAA/NESDIS/STAR to remap I- and M-band imagery from S-NPP and NOAA-20 satellites into the ABI and AHI fixed grid projections with polar2grid for a couple of years. I use the resulting remapped images as part of a process to compute stereo winds and heights over the ABI and AHI domains. The stereo heights are referenced to the ellipsoid and that is why I use the ellipsoid geolocation files. Operations has recently announced that they will no longer be generating the ellipsoid geolocation files for the S-NPP I bands or the NOAA-20/21 imagery. They will only be distributing the terrain-corrected geolocation files. Given this, I had 2 questions for the forum:

1. Were you aware of this change to stop distributing the ellipsoid geolocation files?
2. Are there any plans to update polar2grid to convert the terrain-corrected geolocation data to the ellipsoid?

[kathys]

Hello,

I will try and answer you questions.

> 1. Were you aware of this change to stop distributing the ellipsoid geolocation files?
Yes we are aware of this change. We requested from NOAA information about whether the ADL software will continue to support the creation of the ellipsoid geolocation files. The answer was yes, it will continue to support this. This means the CSPP SDR software will continue to allow the creation of these files.

> 2. Are there any plans to update polar2grid to convert the terrain-corrected geolocation data to the ellipsoid?
There are no plans for polar2grid to support the conversion of terrain-corrected geolocation data to the ellipsoid geolocation data.

Kathy

[wbresky]

Apologies for my ignorance, but what exactly is the ADL software? Is that run locally? Are you saying the ellipsoid files can be created locally by running the ADL software? Thanks.

[jbraun]

Hello,

The NOAA Algorithm Development Library (ADL) allows the operational processing algorithms for the JPSS series of satellites (SNPP, NOAA-20, NOAA-21) to run without modification in a Linux environment. Our CSPP SDR software is based on this ADL software, so you can use (or continue to use) the CSPP SDR software to create the ellipsoid geolocation files from Raw Data Records (RDRs). The SDR software requires the use of the "-g" flag in order to keep these ‘VIIRS-IMG-GEO’ and ‘VIIRS-MOD-GEO’ files.

If you have any questions about the CSPP SDR software, please feel free to reach out to us on the CSPP SDR forum or email us at cspp_issues@ssec.wisc.edu.

Thanks,
Jess

[kathys]

Just for clarity, the primary use case for CSPP software is to support the direct broadcast community. The CSPP SDR software that we release is based upon the underlying ADL software; it is prepared as a stand alone package from the large integrated ADL that is run in NOAA operations. So even if NOAA decides not to distribute the VIIRS Ellipsoid files, the CSPP SDR software will still be capable of producing them.

I hope this helps,

Kathy