Since 2021 the xshooter_mbias recipe is executed with the --pd_noise_compute=TRUE command line option that performs a 2D Fourier transform of each of the five raw BIAS frames and calculates the (not robust) standard deviation and (robust) MAD (median absolute deviation). Both parameters are ingested into the QC1 DB, and the maximum of the five std/stdMAD values (qc_PN_maxrat in the DB) is monitored here .

The purpose of the analysis is to discriminate statistical noise, and non-statistical noise. More information can be found at the plot tutorial page