Peter Weilbacher This recipe combines several separate amplifier images (flat-fields
with special FITS headers containing pico amplifier measurements)
into one master image file and computes the instrumental throughput per
IFU (and slice).
Processing trims the raw data and records the overscan statistics,
subtracts the bias (taking account of the overscan, if overscan is not
"none"), and optionally, the dark from each raw input image, converts
them from adu to count, scales them according to their exposure time,
and combines them using input parameters.
To compute the throughput the image is converted into a pixel table, the
flux is then integrated over the given filter band, and the ratio of the
expected flux (FITS header INS.AMPL2.CURR) to measured flux is taken, in
the same units. If a geometry table was given as input, the relative
area of the IFUs is taken into account when computing the flux per unit
area. The resulting ratio is the instrument efficiency (throughput) and
saved as QC parameters for the whole input image and per slice in the
output pixel table.