THE EXTREME-ULTRAVIOLET SPECTROGRAPH - A RADIAL GROOVE GRATING, SOUNDING ROCKET-BORNE, ASTRONOMICAL INSTRUMENT

The design, calibration, and sounding rocket flight performance of a n ovel spectrograph suitable for moderate-resolution EUV spectroscopy ar e presented. The sounding rocket-borne instrument uses a radial groove grating to maintain a high system efficiency while controlling the ab errations induced when doing spectroscopy in a converging beam. The in strument has a resolution of approximately 2 angstrom across the 200-3 30 angstrom bandpass with an average effective area of 2 cm2. The inst rument, called the Extreme Ultraviolet Spectrograph, acquired the firs t EUV spectra in this wavelength region of the hot white dwarf G191-B2 B and the late-type star Capella.