A SIC variable may be associated with nearly every header parameter.
Variables are normally not enabled; a whole group of variables may be
enabled,
by means of command VARIABLES. For instance:
VARIABLES ATMOS ON
will turn on all variables concerning atmospheric parameters. Use HELP
VARIABLES to consult the list of variables and groups of variables. To
examine the content of variables, the observation, and one of the
associated may be read in with command GET /RECORD.
The edition of the data headers is done is a more powerful way by command MODIFY HEADER. This command will perform a loop on the current index, loading each header in turn; for each it will execute a procedure MODIFY.CLIC, that you should provide (you may give it another name, and enter it as a second argument to command MODIFY). This procedure may contain SIC commands (such as EXAMINE, LET, SAY ...), or some CLIC commands like HEADER, DUMP ... Its execution must end with the special command GO, otherwise the loop will be aborted. The command GO WRITE will ensure that the modified header is rewritten to disk.
For instance, assume the flux for 3C84 was entered incorrectly as 100 Jy, during an observing session (you do not recall when exactly). The correct flux was 12 Jy. Your MODIFY.CLIC might look like:
IF FLUX.NE.12 THEN
LET FLUX = 12
SAY "Flux updated, scan " 'SCAN'
GO WRITE
ELSE
GO
ENDIF
You will have to execute the following commands:
FIND VARIABLE POSITION ON ! this is the group for FLUX VARIABLE GENERAL ON ! this is the group for SCAN MODIFY HEADER
Note that in the above example, the same result could be obtained more
simply
by:
SET FLUX 3C84 12.
STORE FLUX
Command MODIFY DATA works in the same way, but it will successively load all the data records of each observation, and execute (by default) the procedure DATA.CLIC. The range of this command may however be restricted with options /AFTER date time and /BEFORE date time, where `date' is a usual date chain (jj-mmm-yyyy), and `time' the time in hours (sexagesimal notation in understood).