The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 sq deg will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers in turn feed ten broad-band spectrographs. We will describe the methods and results for the commissioning instrument metrology program. The primary goals of this program are to calculate the transformations and further develop the systems that will place fibers within 5μm RMS of the target positions. We will use the commissioning instrument metrology program to measure the absolute three axis Cartesian coordinates of the five CCDs and 22 illuminated fiducials on the commissioning instrument.
We describe the design of the Commissioning Instrument for the Dark Energy Spectroscopic Instrument (DESI). DESI will obtain spectra over a 3 degree field of view using the 4-meter Mayall Telescope at Kitt Peak, AZ. In order to achieve the required image quality over this field of view, a new optical corrector is being installed at the Mayall Telescope. The Commissioning Instrument is designed to characterize the image quality of the new optical system. The Commissioning Instrument has five commercial cameras; one at the center of the focal surface and four near the periphery of the field and at the cardinal directions. There are also 22 illuminated fiducials, distributed throughout the focal surface, that will be used to test the system that will map between the DESI fiber positioners and celestial coordinates. We describe how the commissioning instrument will perform commissioning tasks for the DESI project and thereby eliminate risks.
We describe work at Lawrence Berkeley National Laboratory (LBNL) to develop enhanced performance, fully
depleted, back-illuminated charge-coupled devices for astronomy and astrophysics. The CCDs are fabricated on
high-resistivity substrates and are typically 200–300 μm thick for improved near-infrared response. The primary
research and development areas include methods to reduce read noise, increase quantum efficiency and readout
speed, and the development of fabrication methods for the efficient production of CCDs for large focal planes.
In terms of noise reduction, we will describe technology developments with our industrial partner Teledyne
DALSA Semiconductor to develop a buried-contact technology for reduced floating-diffusion capacitance, as well
as efforts to develop ”skipper” CCDs with sub-electron noise utilizing non-destructive readout amplifiers allowing
for multiple sampling of the charge packets. Improvements in quantum efficiency in the near-infrared utilizing
ultra-high resistivity substrates that allow full depletion of 500 μm and thicker substrates will be described, as
well as studies to improve the blue and UV sensitivity by investigating the limits on the thickness of the back-side
ohmic contact layer used in the LBNL technology. Improvements in readout speed by increasing the number of
readout ports will be described, including work on high frame-rate CCDs for x-ray synchrotrons with as many as
192 amplifiers per CCD. Finally, we will describe improvements in fabrication methods, developed in the course
of producing over 100 science-grade 2k × 4k CCDs for the Dark Energy Survey Camera.