A CLEAN procedure can be used to erase the memory effects of the LW array if it has been illuminated previously with a highly contrasted image.
This procedure consists of a bright flash on the array, always
performed in the same configuration : 1.5 arcsec PFOV, LW7 Filter,
= 2 sec. It lasts 4 minutes in total: 30 sec for
heating the source of the ICD, 30 sec for 15 exposures, 3 minutes
for stabilization.
A CLEAN should be requested by the observer when setting a smaller PFOV after using the 12 arcsec PFOV lens, for which the FOV does not fill the area of the array.
Note that a CLEAN request does not produce any action if the SW channel is selected.