Multilayer grating spectrometer for solar observations

A stigmatic spectrograph in the 17 - 23 nm region for observations of the solar disk and corona based on multilayer mirror and grating is described. Its main scientific use is global surveying of the disk with approximately equal 10 arcsec² resolution. Spectral resolution is used to monitor temperature- and density-sensitive spectral lines thus obtaining solar temperature and density maps in the 10⁵ - 10⁷ degrees Kelvin, 10¹³ - 10¹⁸ cm^-3 ranges, respectively. The use of off-axis paraboloidal telescope coupled with a toroidal grating results in spectral resolving powers of the order of 1000 and angular resolution of approximately equal 10 arcsec throughout an instantaneous field-of-view of 10 arcsec X 40 arcmin. Temporal resolution of the order of 0.1 second is expected which can be of use in observations of high brilliance events. The system is also equipped with a visible channel to correlate XUV events with ground observations.