The DESI Experiment Part II: Instrument Design

Author(s): Collaboration, DESI; Aghamousa, A; Aguilar, J; Ahlen, S; Alam, S; Allen, LE; Prieto, CA; Annis, J; Bailey, S; Balland, C; Ballester, O; Baltay, C; Beaufore, L; Bebek, C; Beers, TC; Bell, EF; Bernal, JL; Besuner, R; Beutler, F; Blake, C; Bleuler, H; Blomqvist, M; Blum, R; Bolton, AS; Briceno, C; Brooks, D; Brownstein, JR; Buckley-Geer, E; Burden, A; Burtin, E; Busca, NG; Cahn, RN; Cai, Y-C; Cardiel-Sas, L; Carlberg, RG; Carton, P-H; Casas, R; Castander, FJ; Cervantes-Cota, JL; Claybaugh, TM; Close, M; Coker, CT; Cole, S; Comparat, J; Cooper, AP; Cousinou, M-C; Crocce, M; Cuby, J-G; Cunningham, DP; Davis, TM; Dawson, KS; Macorra, ADL; Vicente, JD; Delubac, T; Derwent, M; Dey, A; Dhungana, G; Ding, Z; Doel, P; Duan, YT; Ealet, A; Edelstein, J; Eftekharzadeh, S; Eisenstein, DJ; Elliott, A; Escoffier, S; Evatt, M; Fagrelius, P; Fan, X; Fanning, K; Farahi, A; Farihi, J; Favole, G; Feng, Y; Fernandez, E; Findlay, JR; Finkbeiner, DP; Fitzpatrick, MJ; Flaugher, B; Flender, S; Font-Ribera, A; Forero-Romero, JE; Fosalba, P; Frenk, CS; Fumagalli, M | Abstract: DESI (Dark Energy Spectropic Instrument) is a Stage IV ground-based dark energy experiment that will study baryon acoustic oscillations and the growth of structure through redshift-space distortions with a wide-area galaxy and quasar redshift survey. The DESI instrument is a robotically-actuated, fiber-fed spectrograph capable of taking up to 5,000 simultaneous spectra over a wavelength range from 360 nm to 980 nm. The fibers feed ten three-arm spectrographs with resolution $R= \lambda/\Delta\lambda$ between 2000 and 5500, depending on wavelength. The DESI instrument will be used to conduct a five-year survey designed to cover 14,000 deg$^2$. This powerful instrument will be installed at prime focus on the 4-m Mayall telescope in Kitt Peak, Arizona, along with a new optical corrector, which will provide a three-degree diameter field of view. The DESI collaboration will also deliver a spectroscopic pipeline and data management system to reduce and archive all data for eventual public use.