OPTICAL PERFORMANCES OF THE ULTRAVIOLET CORONAGRAPH SPECTROMETER OF THE SOLAR HELIOSPHERIC OBSERVATORY

The optical performances of the spectrometer assembly for the Ultravio let Coronagraph Spectrometer of the Solar and Heliospheric Observatory mission have been tested. The flight unit of the spectrometer assembl y, consisting of the structure equipped with the entrance slits assemb ly, the grating drive mechanisms mounting two toroidal gratings, and t he photon-counting detectors, has been integrated and aligned; also th e flight unit of the White Light Channel has been integrated and align ed in the spectrometer assembly. Tests with both visible and UV radiat ion have been performed. Aberration and stray-light measurements have shown that the instrument performs satisfactorily, almost in complianc e with the scientific requirements; also some measurements of the pola rimeter modulation curve and the relative error have shown performance s within the specified requirements. (C) 1997 Optical Society of Ameri ca