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  • Discussion topic - easy ways to find data gaps in Earth-observing instrument data sets
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Most data sets from Earth observation instruments on satellites will have at least a few gaps that break up the continuity of the data.   These gaps can result from satellite or instrument "safeholds", when the satellite was not transmitting data or the instrument was inoperative.  Some data gaps result from maneuvers made by the satellite to maintain its orbit or conduct a calibration.  Data gaps can also be the result of different observational modes for certain instruments.  Data gaps can also occur in multi-satellite data sets when one instrument's data was replaced by another instrument.

This discussion was inspired by a question from a user asking about data gaps in the SeaWiFS ocean color data set.  In the next post (to be posted on September 14I will describe a very easy way to see where data gaps are in the SeaWiFS data set.  Then we will ask other data scientists and users for their techniques to find and keep track of gaps in the data sets they use.

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  1. Regarding the SeaWiFS data set, NASA's Ocean Biology DAAC (OB.DAAC) provides a visual method to browse all of the SeaWiFS Level 3 data files (daily, 8-day, monthly, etc.) in their Level 3 Browser,  You may select a SeaWiFS data product, and then select the Monthly time resolution, and view the thumbnail images to see the months later in the mission where data is missing, due to satellite safehold and communication issues.  This same method can be used for any of the other missions represented in their browser (MODIS-Aqua, OCTS, CZCS, Suomi-NPP VIIRS), and can even locate missing daily data, if information about a particular date is required.

  2. The implication being that what is deployed at OB.DAAC for SeaWiFS data can be easily deployed to other DAACs for other instrument data sets. At this point without further information that may be a bit of an oversell but additional investigation may be warranted.

  3. This means that the CVFFS has been published in OB.DAAC data, which can be easily implemented in DAACs of other data data sets. At this stage, without further information, this may be the type of additional supply but additional research can be justified.