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.