SOHO CDS-NIS IN-FLIGHT INTENSITY CALIBRATION USING A PLASMA DIAGNOSTIC METHOD

The internal intensity calibration of the Coronal Diagnostic Spectrome ter (CDS) - Normal Incidence Spectrometer (NIS) is studied using the A rcetri diagnostic method. A large number of spectral lines observed by the CDS-NIS 1 and NIS 2 windows in a solar active region is analysed in order to determine the intensity calibration curve for both channel s. The plasma diagnostic method developed in Arcetri allows the measur ement of the correction factors to the preliminary CDS-NIS internal in tensity calibration curves and the determination of the relative calib ration between NIS 1 and NIS 2, A further correction factor of approxi mately three is found to be necessary for a correct intercalibration o f the two wavelength windows. Also the NIS 2 second-order sensitivity is measured. The Arcetri diagnostic method proves to be a powerful too l for intensity calibration studies.