DESI Commissioning Instrument Metrology

TL;DR

The paper details the metrology methods used to precisely calibrate the DESI commissioning instrument, ensuring fiber positioning accuracy within 5 micrometers for optimal spectroscopic measurements in a large-scale cosmological survey.

Contribution

It introduces a novel metrology approach for the DESI instrument, achieving high-precision fiber placement calibration crucial for accurate cosmological observations.

Findings

Achieved fiber positioning accuracy within 5 micrometers RMS.

Developed calibration procedures for CCD and fiducial coordinate measurements.

Enhanced the precision of the instrument's fiber placement system.

Abstract

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 5um 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.