Provides a better estimate of the common-mode (" COM" ) signal, by excluding samples that fall within fixed regions on the sky specified by an external mask
If com.zero_mask is set to one of " REF" , " MASK2" or " MASK3" then an NDF will be obtained using the specified ADAM parameter (REF, MASK2 or MASK3) and used as a user-defined mask. Setting com.zero_mask to an integer value larger than zero has the same effect as setting it to " REF" . Setting it to an integer less than or equal to zero results in no external mask being used with the COM model. Note, using " REF" ensures that the mask and the output image of MAKEMAP are on the same pixel grid - using " MASK2" or " MASK3" does not provide this guarantee (it is then the users responsibility to ensure that the supplied masks are aligned with the output image in pixel coordinates). The pixels in the map that are to be included in the common-mode estimation should be set to the bad value in the mask. All other pixels will be excluded from the COM estimation. [0]