This descriptor specifies the state of filter temperature control. It contains the value 'REGULATED' if filter temperature is regulated; 'MEASURED' if filter temperature is measured; and 'DOME' if filters are unregulated, and approximately at dome temperature.
If FILTSTAT= 'REGULATED', there may be a Real*4 descriptor named FILTTEMP in the instrumental ``.tbl'' file, giving the temperature of the set-point in kelvins. If FILTSTAT= 'MEASURED', there should be a data column named FILTTEMP in the data files (see next section) that contains the measured filter temperature.
Table: All possible Descriptors for the instrumental ``.tbl'' file