The last frame correction step is only applied to MIRI data and flags the final group in each integration as bad (the “DO_NOT_USE” bit is set in the GROUPDQ flag array), but only if the total number of groups in each integration is greater than 2. This results in the data contained in the last group being excluded from subsequent steps, such as jump detection and ramp fitting. No flags are added if NGROUPS <= 2, because doing so would leave too few good groups to work with in later steps.
Only the GROUPDQ array is modified. The SCI, ERR, and PIXELDQ arrays are unchanged.