The DESI Experiment Part II: Instrument Design
  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.
