THE WAVELENGTH CALIBRATION AND RESOLUTION OF THE SWS

The laboratory wavelength calibration of the SWS has been successfully transferred to the in orbit situation. The achieved accuracies for th e grating sections are lambda/delta lambda similar to 10000. Any remai ning errors in the wavelength scale are dominated by uncertainties of the relative position of the target in the 14'' - 20'' wide slits. The grating spectral profile is very well represented by a Gaussian shape . The width of the grating spectral profile can be accurately predicte d by a theoretical model. The wavelength calibration of the FP's is ac curate to within 1/3 Of a resolution element, corresponding to lambda/ delta lambda similar to 10(5). The wavelength stability of the grating s and FP is excellent, no measurable changes were found during the fir st 6 months of the ISO mission.