AST 9420645 ABSTRACT This project will design, build, and install a versatile and efficient Medium Resolution Spectrograph (MRS) for the 9-m Hobby-Eberly telescope (HET). This instrument will cover the entire visible spectrum from 350 to 1100 nm (with a clear upgrade path for use at 1800 nm), have a resolution range from 3000 < lambda/ delta-lambda < 18000, and reside in an environmentally controlled spectrograph room. Optical fibers will couple the spectrograph to the telescope; operating modes for the instrument will include single object, synthetic long slit, and multiple object spectroscopy. Because of the need for both spectral coverage and resolution, the MRS will be a dual beam system (split at 590 nm), with a grating cross-dispersed echelle, and a white-pupil that controls vignetting losses while keeping the sizes of costly optical elements small. This configuration is both economical and highly efficient. The MRS will be designed to take maximum advantage of the high efficiency optics and queue scheduled nature of the HET. Among its many programs, the MRS will 1) explore the broad line regions of active galactic nuclei and quasars through dense time sample spectroscopy, 2) examine the evolution of large scale structure in the universe through measurements of quasar absorption lines, 3) detect and characterize the properties of dark matter via kinematical measurements in elliptical galaxies, and 4) measure the age and dynamical evolution of the Milky Way through kinematical study of white dwarfs,.
