EUV and soft x-ray telescope-spectrometer for imaging spectroscopy on the Solar Orbiter mission: configurations with multilayer-coated optics

Two configurations with multilayer-coated optics for an EUV and soft X-ray telescope-spectrometer for imaging spectroscopy on the Solar Orbiter mission are presented. The telescope is designed with conventional grazing-incidence optics, in order to reduce the thermal load on optics looking directly at the solar disk. The spectrometer mounts a normal-incidence multilayer-coated grating, being protected by the entrance slit. Two configurations are presented: a grazing-incidence telescope that feeds a normal-incidence grating spectrometer and two grazing-incidence telescopes with cylindrical mirrors in the Kirkpatrick-Baez configuration and a normal-incidence spectrometer with a cylindrical grating. In the former case, the off-axis resolution of the telescope is degraded by the grating aberrations. In the latter case, the spectral and spatial focusing properties are fully uncoupled: the off-axis resolution is independent from the grating performance. The performance in the 18-22 nm spectral region are compared with those of a grazing-incidence telescope-spectrometer.