MODIST geo files?

alaroy · by **alaroy** » Wed Sep 02, 2020 2:34 pm America/New_York

Are geo files for MODIST available for download from oceandata? If so where should I be looking?

Or does one need to make their own from the two hourly attitude and ephemeris files?

Thank you!

-Andrew L.

by **OB ODPS - jgwilding** » Wed Sep 02, 2020 3:23 pm America/New_York

Hi Andrew.

Yes, you need to create the GEO files for MODIS using the ATT/EPH data. If you're using SeaDAS to process the data, i believe the scripts do that for you.

john

alaroy · by **alaroy** » Wed Sep 02, 2020 4:37 pm America/New_York

John,

Thank you for the quick reply!

Just out of curiosity, why does MODISA get 5 minute attitude and ephemeris files while MODIST gets 2 hour ones?

-Andrew L.

by **OB ODPS - jgwilding** » Wed Sep 02, 2020 5:07 pm America/New_York

I believe it comes down to they are on different spacecraft platforms. The Aqua data stream includes the near-real-time (NRT) ATT/EPH data that can be used to process data. Then later the refined ATT/EPH data are delivered, and any future refined L2 processing we do uses the refined ATT/EPH. Terra also has ATT/EPH data embedded in the data stream, and up to several years ago, those could be used to process the data NRT. The geo-location software no longer supports using that data. I don't know the details of why. It might be that the accuracy of the onboard data had become bad enough to use without some post processing.

john