The FOT is a sequence of tape files, each one separated by a tape mark, and terminated by a double tape mark.
Physically each file is in "fixed blocked" format, i.e. all tape blocks are of the same
length (in a file; this length may differ from one file to another) with the exception
of the last block which may be shorter. All block lengths are multiple of a common logical record length.
The filing process is essentially the unblocking and the reconstruction of disk files with the original record lengths.
The instrument order is typically by increasing energy (LECS MECS HPGSPC PDS) or number (WFC1 WC2). NFI and WFC data are never mixed on the same FOT.