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We describe a space-borne solar observatory, the Ultra High Resolution XUV Spectroheliograph (UHRXS), which has been selected by NASA for flight among the initial scientific instruments to be placed on the space station Freedom. The principal UHRXS instruments are nine XUV multilayer Ritchey-Chrétien telescopes covering the spectral range from ~70 to ~350 Å; each telescope is able to isolate line multiplets, within a narrow wavelength interval, excited over a narrow temperature range, providing full disk images of diagnostic quality covering structures in the solar atmosphere ranging in temperature from T ~ 50,000 K (He II, ? ~ 304 Å) to 20,000,000 K (Fe XXIV, ? ~ 192 Å). The XUV images will be recorded on high resolution 70 mm format film, allowing resolutions as high as 0.1 arcsec to be achieved for a 1.0° field. The XUV images will be supplemented by (i) full disk high resolution (~0.1 arcsec) far ultraviolet images in H I Ly ? (? - 1216 Å) and C IV (? ~ 1548/1550 Å), (ii) full disk soft x-ray images in four bands in the interval ?? ~ 6 to 70 Å, and (iii) electronically recorded high resolution (?/?? > 10,000) spectrohelio-grams in 2 XUV, 1 EUV (~450 to 1100 Å) and 2 FUV (~1100 to 1600 Å) bands. The electronically recorded images will use the multi-anode multichannel array detector. We propose to utilize the resulting data sets to address fundamental problems related to the following solar phenomena: (i)the fine structure of the solar chromosphere/corona interface, (ii) the structure, energetics, and evolution of high temperature coronal loops,
(iii) the large scale structure and dynamics of the corona, including the solar wind interface, the magnetic field, and coronal mass ejections, and
(iv) solar flares, especially the preflare state, the impulsive release of energy, and the evolution of postflare loops.
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