Clarification on MCD19A2 Orbit_time_stamp and Its Association with MODIS Swath Observation Times

[zxc_manchester]

Hi, I am working with the MODIS MAIAC MCD19A2 Collection 6.1 product and need to associate the orbit-level AOD/QA information in each MCD19A2 tile with the corresponding Terra/Aqua MODIS swath observations (e.g., MOD03/MYD03 and MOD021KM/MYD021KM). I have been using the Orbit_time_stamp information in MCD19A2 to identify the corresponding swaths, initially assuming that the reported Terra/Aqua orbit times should approximately match the acquisition times of the swaths that actually cover the same MODIS tile. However, I have found several cases where this does not appear to be true. For example, "MCD19A2.A2010035.h16v07.061.2022329072837.hdf", the Aqua orbit times parsed from the product are 20100351530A and 20100351535A, whereas the Aqua swaths that actually spatially cover this tile (h16v07) occur around 13:55 UTC.
I observed a similar mismatch for tile h21v08 (MCD19A2.A2010034.h21v08.061.2022329093311.hdf) on the same day, the Aqua orbit times parsed from the product are 20100351030A and 20100351210A, while the indeed the Aqua orbit times parsed from the product are 20100351035A and 20100351210A.

Other MCD19A2 files also show that the orbit times obtained from MCD19A2 do not always correspond to all swaths that spatially cover the tile. This creates a problem when trying to use the orbit-specific MCD19A2 AOD/QA masks together with MODIS viewing geometry and L1B reflectance data, because matching the datasets based only on the reported MCD19A2 orbit time can miss the actual corresponding swath. Could you please clarify the exact definition of Orbit_time_stamp in MCD19A2? In particular, does it represent the actual Terra/Aqua overpass time for the pixels contained in that tile, or does it have a different meaning or orbit association? Is there an officially recommended method for determining which MOD03/MYD03 and MOD021KM/MYD021KM swath granules correspond to each orbit layer in an MCD19A2 tile? Any clarification on how the orbit-specific layers in MCD19A2 should be linked to the original MODIS swath observations would be greatly appreciated.