I'm downloading the MODIS derived Albedo 16-Day L3 Global 500 m resolution product. I expected to have a dataset for dates every 16 days. Instead I have datasets every 8 days as can be seen in the image I uploaded.

The info on the product (link) does state:

Phased production strategy: Produced every 8 days with 16 days of acquisition (i.e., production period 2001001 includes acquisition between Days 001 and 016, production period 2001009 includes acquisition between Days 009 and 024)

So every 8 days a dataset is released which contains the previous 16 days of data? so each of these datasets have a data overlap of 8 days?

enter image description here

  • Sounds like its working as expected, but I'm confused about the title vs the description - it says there is a product released every 8 days with the last 16 days of data. Can you explain what the issue you have is? Also, can you add details to the question about how you're defining and measuring periodicity?
    – BradHards
    Dec 31, 2014 at 3:21
  • I modified my question a bit, I hope it clarifies what I'm inquiring about.
    – JEquihua
    Dec 31, 2014 at 4:10

2 Answers 2


Most surfaces reflect anisotropically, so their reflectance varies with the angle between illumination and viewer (ie, Sun and MODIS sensor). MODIS's wide swath means that it is able to view every location on the ground every day, albeit from different orbit tracks (which have a 16-day repeat interval). Observations recorded from these sets of 16 different look-angles, from the MODIS sensors on both the Terra and Aqua satellites, are used to approximate the variation of reflectance with relative illumination / viewing angles (described by the Bidirectional Reflectance Distribution Function, BRDF). So each dataset release provides albedo estimates based on the BRDF approximation built-up over the previous 16 days. These sets are overlapped by 8 days - so for example, if the first release is on the 17th January, derived from observations taken from 1st - 16th, then the next will be on the 25th January, using observations from 9th - 24th.


The link is telling you exactly that.

So the Mosaic_2000-03-13.hdf file has 16 days of data. Of those 16 days of data, half of that (the first 8 days) will also be found in Mosaic_2000-03-05.hdf, and the half (the second 8 days) will also be in Mosaic_2000-03-21.hdf.

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