If curves are available for the filters used, this holds the name of a MIDAS catalog file that points to individual table files, which in turn hold the transmission data.
The individual filter table files should give transmittance (column name TRANS) as a function of wavelength in nanometers (column name LAMBDA). Each filter's table file should contain a character descriptor named BAND that names the passband for which that filter is used.
If no filter curves are available, FILTCAT should contain only spaces.