Hello,
I was wondering if there were options or a simple way to force the viirs_sdr script to utilize older LUT values for processing. I wanted to test different versions of the LUTs and see how calibration has changed overtime. I tried running VIIRS SDR processing in offline mode with older LUT values, but it didn't seem to utilize the older LUT values. Does the processing script only look for a certain date range? Would it be possible to override this or force it to use outdated LUTs?
Thanks,
Andrew
Offline usage of legacy LUTs
Re: Offline usage of legacy LUTs
Hello Andrew,
Can you tell me which LUTs you are interested in? This process is complicated by:
1). Often times the LUTs are not compatible between different versions of ADL. That is why we have new LUT download https sites for new CSPP versions. We are on LUT site number 6 now. In the CSPP Installation guides we provide information on the start date of support for the JPSS instruments for each release.
2). The ADL software will choose the LUTs that fit the data being processed the best. The LUT update intervals vary greatly. Some are updated monthly, and some are updated once a mission.
Kathy
Can you tell me which LUTs you are interested in? This process is complicated by:
1). Often times the LUTs are not compatible between different versions of ADL. That is why we have new LUT download https sites for new CSPP versions. We are on LUT site number 6 now. In the CSPP Installation guides we provide information on the start date of support for the JPSS instruments for each release.
2). The ADL software will choose the LUTs that fit the data being processed the best. The LUT update intervals vary greatly. Some are updated monthly, and some are updated once a mission.
Kathy
Re: Offline usage of legacy LUTs
Hi Kathy,
I'm primarily interested in the dynamic VIIRS LUTs for JPSS-02 , if I'm not mistaken this would be the DNB darks/flats (DN0), DNB Gain ratios, stray light corrections, and maybe a few other files. Is there a way to set which LUTs or range of dates for LUTs to use? I primarily use this to look at how LUTs have changed overtime, how new calibration impacts VIIRS imagery, and how greatly it impacts higher level products.
Thanks,
Andrew
I'm primarily interested in the dynamic VIIRS LUTs for JPSS-02 , if I'm not mistaken this would be the DNB darks/flats (DN0), DNB Gain ratios, stray light corrections, and maybe a few other files. Is there a way to set which LUTs or range of dates for LUTs to use? I primarily use this to look at how LUTs have changed overtime, how new calibration impacts VIIRS imagery, and how greatly it impacts higher level products.
Thanks,
Andrew
Re: Offline usage of legacy LUTs
Okay Andrew, I think I understand.
I am not sure that the CSPP software is the best one to use for your investigation. The main use case for this work is supporting the near-real-time direct broadcast community which means things like we provide only one "VIIRS-RSBAUTOCAL-HISTORY-AUX" LUT file for each VIIRS instrument per day. These files are used for Visible and DNB calibration, and are available for each orbit. But we do not get access to these files until well after real-time, so we only provide one per day. This does not make a huge difference in reflectances, but if you plan to do a calibration investigation, I suggest that you use the archived data available from NOAA.
If you want to pursue this, please keep in mind what I said above, and let me know. We can provide you with instructions directly using your email address.
Kathy
I am not sure that the CSPP software is the best one to use for your investigation. The main use case for this work is supporting the near-real-time direct broadcast community which means things like we provide only one "VIIRS-RSBAUTOCAL-HISTORY-AUX" LUT file for each VIIRS instrument per day. These files are used for Visible and DNB calibration, and are available for each orbit. But we do not get access to these files until well after real-time, so we only provide one per day. This does not make a huge difference in reflectances, but if you plan to do a calibration investigation, I suggest that you use the archived data available from NOAA.
If you want to pursue this, please keep in mind what I said above, and let me know. We can provide you with instructions directly using your email address.
Kathy
Re: Offline usage of legacy LUTs
Hi Kathy,
That would be great, I would love some instructions/advice for how to properly look into this, do you need my email directly or do you have access to it?
Thanks,
Andrew
That would be great, I would love some instructions/advice for how to properly look into this, do you need my email directly or do you have access to it?
Thanks,
Andrew
Re: Offline usage of legacy LUTs
We do have it Andrew, and will send you the instructions.
Cheers,
Kathy
Cheers,
Kathy
Re: Offline usage of legacy LUTs
Hello again Andrew,
Sorry that we have not gotten back to you before now. We considered the best way to advise you in using legacy LUTs with the VIIRS CSPP SDR software, and we found that there really is no easy way to do this. It is possible to provide a date to `sdr_luts.sh -t `, which will download LUTs with effectivity dates that are close to the date that you provide, but during the initial installation the software downloads the most recent files that are available to start with. There are also LUTs which determine whether to use the "VIIRS-RSBAUTOCAL-HISTORY-AUX" for VIIRS calibration or not, and this varies with instrument, and at least one has been updated within the last 6 months. Some of the effectivity dates are back dated, meaning even if they were issued recently, they are back dated so that earlier dates will use the files too, and the ADL software will choose those during SDR execution.
Since this was never a use case that we were funded to support, and because of the complexity that would be involved in determining how to do this, I am afraid we are not going to be able to provide you with a good solution.
I am sorry,
Kathy
Sorry that we have not gotten back to you before now. We considered the best way to advise you in using legacy LUTs with the VIIRS CSPP SDR software, and we found that there really is no easy way to do this. It is possible to provide a date to `sdr_luts.sh -t `, which will download LUTs with effectivity dates that are close to the date that you provide, but during the initial installation the software downloads the most recent files that are available to start with. There are also LUTs which determine whether to use the "VIIRS-RSBAUTOCAL-HISTORY-AUX" for VIIRS calibration or not, and this varies with instrument, and at least one has been updated within the last 6 months. Some of the effectivity dates are back dated, meaning even if they were issued recently, they are back dated so that earlier dates will use the files too, and the ADL software will choose those during SDR execution.
Since this was never a use case that we were funded to support, and because of the complexity that would be involved in determining how to do this, I am afraid we are not going to be able to provide you with a good solution.
I am sorry,
Kathy