Small pitch tilting spine optical fiber positioners for massively parallel spectroscopy

Massively-multiplexed spectroscopic surveys rely on precise optical fiber-positioning technology to match the fiber positions in physical space to targets observed on-sky. Several different technologies have been used for such devices, including Tilting Spines, Twirling Posts, and Walking Bugs; each of these has its own advantages and drawbacks in terms of parallelization, pitch, exclusion radius, and other relevant operational factors. Current instruments using Tilting Spines operate with a pitch (that is, the separation between adjacent spines) of approximately 9 mm. Reducing the pitch to 5 mm allows for observations of many more targets in parallel, as well as (potentially) much denser target fields. Here we describe engineering efforts and progress towards reducing the pitch between adjacent Tilting Spines. We conclude with a brief discussion of the impact an instrument with very densely packed fiber positioners would have on massively-multiplexed astronomical observations.