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LAnce NRT VJ109 file drop out

Posted: Wed Mar 05, 2025 6:44 pm America/New_York
by vllgsbr2
The lance nrt skips many VJ109 NRT files. There can be several 6 minute granules not posted, but for the VJ103MOD NRT files all 6 minute intervals have a full sized file. Some files are really small in size for VJ109_NRT ~ 5.34MB instead of the usual 230MB to 320MB (attached image). Is there a reason? I want the 19Z to 22Z files for my study ___domain over the western US. I believe its all daytime granules and from what I've downloaded some files are all Ocean and some mixed or just land which is what I expected. Below are the link I'm using. Is there a better data source for these files?

VJ109_NRT
https://nrt3.modaps.eosdis.nasa.gov/archive/allData/5200/VJ109_NRT/2025/060/
VJ103MOD_NRT
https://nrt3.modaps.eosdis.nasa.gov/archive/allData/5201/VJ103MOD_NRT/2025/060/

Re: LAnce NRT VJ109 file drop out

Posted: Thu Mar 06, 2025 12:06 pm America/New_York
by LAADS_UserServices_M
Data granules are Day mode, Night mode, and Both (day and night) mode. For Level 2 Land Surface Reflectance (LSR) products (i.e., VJ109) we do not process Night mode granules and that’s why there are fewer VJ109 files than the VJ103MOD (geolocation) files for a given data day.
Similarly, if the granule corresponds to a “Both” mode granule, then the LSR will only contain the data that is for the Day mode scans within that granule and will cause the output to be smaller. The 2006 and the 2054 granules on your screenshot are Both mode granules.
Granules that are not Night mode that intersect the period you are interested in are 19:12 through 21:48.

Re: LAnce NRT VJ109 file drop out

Posted: Thu Mar 06, 2025 12:16 pm America/New_York
by vllgsbr2
thanks for the clarification! I did not know this.