UC Berkeley

The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the universe using the baryon acoustic oscillations technique. The spec- tra of 35 million galaxies and quasars over 14,000 square degrees will be measured during a 5-year survey. A new prime focus corrector for the Mayall telescope at Kitt Peak National Observatory will deliver light to 5,000 individually targeted fiber-fed robotic positioners. The fibers in turn feed ten broadband multi-object spectrographs. This thesis details origi- nal work done in support of the DESI experiment, both for the instrument and survey design and optimization. First, I describe a novel approach for connecting optical fibers using fusion splicing, a method that will be implemented on DESI. Then, I will describe the ProtoDESI experiment, an on-sky technology demonstration with the goal to reduce technical risks asso- ciated with aligning optical fibers with targets using robotic fiber positioners and maintaining the stability required to operate DESI. The ProtoDESI prime focus instrument, which was installed and commissioned on the 4-m Mayall telescope from 2016 August 14 to September 30, consisted of three fiber positioners, illuminated fiducials, and a guide camera. ProtoDESI was successful in acquiring targets with the robotically positioned fibers and demonstrated that the DESI guiding requirements can be met. Finally, I will describe a predictive sky background model for DESI, which is built on the spectra from the 5-year Baryon Oscilla- tion Spectroscopic Survey (BOSS). This dataset consists of ∼1 million unique sky spectra covering 360 - 1040 nm collected in a variety of observational conditions. We measure an inter-airglow line continuum value of ∼ 0.81×10−17erg/cm2/s/ ̊A/arcsec2 in dark time across the full wavelength range, with a variance of ∼ 0.175 × 10−17erg/cm2/s/ ̊A/arcsec2. The de- tailed model, which accounts for 50% of the variance, shows that the dark sky continuum consists of ∼ 30% zodiacal light and is significantly impacted by solar activity. The improved spectroscopic sky background model can be used in simulations and forecasting for DESI and other surveys.