Correcting Turbulence-induced Errors in Fiber Positioning for the Dark Energy Spectroscopic Instrument

TL;DR

This paper presents a method to significantly reduce turbulence-induced errors in fiber positioning for the DESI survey, improving accuracy and survey speed by leveraging stationary positioners and turbulence correlation.

Contribution

The authors introduce a novel correction technique that minimizes turbulence effects on fiber position measurements, enhancing accuracy and efficiency in fiber-fed spectroscopic surveys.

Findings

Positioning errors reduced from 7.3 to 3.5 microns

Survey speed increased by 1.6%

Effective turbulence correction method demonstrated

Abstract

Highly-multiplexed, robotic, fiber-fed spectroscopic surveys are observing tens of millions of stars and galaxies. For many systems, accurate positioning relies on imaging the fibers in the focal plane and feeding that information back to the robotic positioners to correct their positions. Inhomogeneities and turbulence in the air between the focal plane and the imaging camera can affect the measured positions of fibers, limiting the accuracy with which fibers can be placed on targets. For the Dark Energy Spectroscopic Instrument, we dramatically reduced the effect of turbulence on measurements of positioner locations in the focal plane by taking advantage of stationary positioners and the correlation function of the turbulence. We were able to reduce positioning errors from 7.3 microns to 3.5 microns, speeding the survey by 1.6% under typical conditions.