The name of an existing keyword in the FITS extension whose value is to be reported. A name may be compound to handle hierarchical keywords, and it has the form keyword1.keyword2.keyword3 etc. The maximum number of keywords per FITS card is 20. Each keyword must be no longer than 8 characters, and be a valid FITS keyword comprising only alphanumeric characters, hyphen, and underscore. Any lowercase letters are converted to uppercase and blanks are removed before comparison with the existing keywords.
KEYWORD may have an occurrence specified in brackets
 following the name. This
enables the values to be obtained for keywords that appear more than once. Note that it
is not normal to have multiple occurrences of a keyword in a FITS header, unless it is
blank, COMMENT or HISTORY. Any text between the brackets other than a positive integer
is interpreted as the first occurrence.
The suggested value is the current value.