The DROOPRES module is intended to correct residual droop (see Section 5.1.6 on DROOPOP). The residual droop is assumed to take the form of additive offsets in each of the four read-out channels. The DROOPRES module computes a trimmed average from the un-illuminated regions of the array for each read-out channel. This trimmed average is subtracted from all the pixels belonging to that read-out channel.
The un-illuminated regions of the array are specified by the umask. DROOPRES also ignores bad pixels specified by the pmask.
In the IRS pipelines, the trimmed average is computed for the central 80% of data values in the un-illuminated regions. The outputs of this module are the 2-dimensional files droop.fits and drunc.fits.