May speed up convergences by excluding samples that correspond to high SNR
pixels in the map SSN.ZERO_SNR
"
ssn.zero_snr_ffclean"
.
Note, the SNR values are only available once a map has been created, and so using this parameter
results in no SSN masking on the first iteration. Consequently the map at the end of the first iteration
may have noticable straight lines aligned with azimuth that pass through bright sources, since no SSN
masking was done. Normally, these lines would polute the AST model derived from the map, and
thus polute the residuals on the next iteration, resulting in the lines remaining in later maps. To avoid
this, parameter "
ast.skip"
can be set to a positive value. This causes the AST model to be skipped
(i.e. no AST signal is subtracted from the residuals) for the first "
ast.skip"
iterations. This
means that a good SSN mask can be formed from these initial iterations before any AST
model is calculated and used. [0.0]