This attribute
indicates whether or not cards should be removed from the
FitsChan if an error occurs within
AST_READ. A succesful read on a FitsChan always results in the removal of the cards which were
involved in the description of the returned
Object. However, in the event of an error during the read
(for instance if the cards in the FitsChan have illegal values, or if some required cards are missing) no
cards will be removed from the FitsChan if the Clean attribute is zero (the default). If Clean is
non-zero then any cards which were used in the aborted attempt to read an object will be
removed.
This provides a means of " cleaning" a FitsChan of WCS related cards which works even in the event
of the cards not forming a legal WCS description.