Between 20 June 1984 and 1 April 1988 (Goddard), or between some time in 1984 and 14 September 1988 (VILSPA), data were processed with the wrong dispersion constants. This means that the wavelengths may need correction. The dispersion constant correction program (DCCOR) will check your data to see whether or not the correction is needed, and set a flag in your H vector accordingly. If the correction is needed, it will correct your wavelengths. This correction applies to SWP and LWR data of both dispersions.
The parameter DELTAW is the correction factor to be subtracted from your wavelengths.