<title>Calibrations and flight performance of the extreme ultraviolet opacity rocket</title>

Abstract

ABSTRACT A sounding rocket observation of G191-B2B, a hot white dwarf star, was made on 27 September 1999 over a wavelengthrange of 220-340 A with the Extreme ultraviolet Opacity Rocket (EOR), an EUV spectrograph. EOR acquired over 200seconds of data above 200 km. Two broadband multilayer-coated diffraction gratings in Wadsworth mounts provide EORwith a peak effective area of 2.5 cm2 near 280 A and spectral resolution of XJEX=2500-3000. Preliminary examination of theflight spectrum suggests the presence of absorption features which are not apparent in lower resolution spectra.Keywords: ultraviolet, spectrograph, multilayer coatings, sounding rocket INTRODUCTION Hot, metal rich, DA white dwarf stars are an interesting class of objects whose extreme ultraviolet (EUV) emission cannot beunderstood thoroughly with observations made by current instrumentation. For example, observations of G191-B2B madewith The Extreme Ultraviolet Explorer (EUVE) lack the spectral resolution to enable positive absorption line identificationsof individual metal species where the metal species have the strongest effect on the emergent EUV spectrum. Subsequently,current models are unable to measure abundances of the EUV absorbers unambiguously2. To make positive identificationswill require new, higher resolution, EUV spectrographs.Instrument sensitivity is the greatest obstacle to performing EUV spectroscopy for two reasons: First, EUV sources are faint.