Indirect processing uses an estimate of static pointing errors (i.e. geometric calibration).
Direct processing uses ground control points within the flight line of interest.
The file name structure is as follows:AirMSPI_ER2_GRP_ELLIPSOID_yyyymmdd_hhmmssZ_tttt_aaa[A,N,F]_Fff_Vvvv.hdf
hhmmss: Hour-minute-second in UTC of the central observation
tttt: Target name
aaa: Mean viewing angle (reported to the nearest tenth of a degree x 10)
Fff: File format version
Vvvv: Version number
For more information, see the Data Product Specifications (DPS)