The Aqua MODIS Level 1A data set contains the same data as the corresponding L0
files, but organized by scan rather than by raw data packets. An entire scan
is stored in the L1A file covering the start of the that scan, even if some of
the L0 packets that made up that scan were from the following 5-minute time
interval. Quality indicators are added to the data to indicate missing or bad
pixels and instrument modes.
Data set information: http://mcst.gsfc.nasa.gov/