The Far Ultraviolet Spectroscopic Explorer satellite observes light in the far-ultraviolet spectral region, 905 -1187 Å with high spectral resolution. The instrument consists of four coaligned prime-focus telescopes and Rowland spectrographs with microchannel plate detectors. Two of the telescope channels use Al:LiF coatings for optimum reflectivity from approximately 1000 to 1187 Å and the other two use SiC coatings for optimized throughput between 905 and 1105 Å. The gratings are holographically ruled to largely correct for astigmatism and to minimize scattered light. The microchannel plate detectors have KBr photocathodes and use photon counting to achieve good quantum efficiency with low background signal. The sensitivity is sufficient to examine reddened lines of sight within the Milky Way as well as active galactic nuclei and QSOs for absorption line studies of both Milky Way and extra-galactic gas clouds. This spectral region contains a number of key scientific diagnostics, including O VI, H I, D I and the strong electronic transitions of H 2 and HD.

The launch of the Far Ultraviolet Spectroscopic Explorer (FUSE) has been followed by an extensive period of calibration and characterization as part of the preparation for normal satellite operations. Major tasks carried out during this period include the initial coalignment, focusing, and characterization of the four instrument channels and a preliminary measurement of the resolution and throughput performance of the instrument. We describe the results from this test program and present preliminary estimates of the on-orbit performance of the FUSE satellite based on a combination of these data and prelaunch laboratory measurements.

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The Cosmic Origins Spectrograph (COS) was installed in the Hubble Space Telescope in May, 2009 as part of Servicing Mission 4 to provide high sensitivity, medium and low resolution spectroscopy at far-and nearultraviolet wavelengths (FUV, NUV). COS is the most sensitive FUV/NUV spectrograph flown to date, spanning the wavelength range from 900 Å to 3200 Å with peak effective area approaching 3000 cm 2 . This paper describes instrument design, the results of the Servicing Mission Orbital Verifi-

The Far Ultraviolet Spectroscopic Explorer (FUSE) ultraviolet spectra of eight giant and supergiant stars reveal that high-temperature (3 ; 10 5 K) atmospheres are common in luminous cool stars and extend across the colormagnitude diagram from Car ( F0 II) to the cool giant Tau ( K5 III). Emission present in these spectra includes chromospheric H Ly, Fe ii, C i, and transition region lines of C iii, O vi, Si iii, and Si iv. Emission lines of Fe xviii and Fe xix signaling temperatures of $10 7 K and coronal material are found in the most active stars, Cet and 31 Com. A short-term flux variation, perhaps a flare, was detected in Cet during our observation. Stellar surface fluxes of the emission of C iii and O vi are correlated and decrease rapidly toward the cooler stars, reminiscent of the decay of magnetically heated atmospheres. Profiles of the C iii k977 lines suggest that mass outflow is underway at T $ 80; 000 K and the winds are warm. Indications of outflow at higher temperatures (3 ; 10 5 K) are revealed by O vi asymmetries and the line widths themselves. High-temperature species are absent in the M supergiant Ori. Narrow fluorescent lines of Fe ii appear in the spectra of many giants and supergiants, apparently pumped by H Ly, and formed in extended atmospheres. Instrumental characteristics that affect cool star spectra are discussed.

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