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Question:

Why is the cloud cover reported as "0.00" for night scenes?

Answer:

The C Function of Mask (CFMask) cloud cover algorithm is used for Landsat Collection 1 Level-1 Landsat 4-5 Thematic Mapper (TM), Landsat 7 Enhanced Thematic Mapper Plus (ETM+), and Landsat 8 Operational Land Imager (OLI)/Thermal Infrared Sensor (TIRS) data products to allow for consistent results.