Recent developments with Cornell’s ZEUS-2 spectrometer at APEX

We present recent developments on Cornell’s 2nd generation z (redshift) and Early Universe Spectrometer (ZEUS-2). ZEUS-2 is a long-slit echelle-grating spectrometer, originally implemented to deliver R∼1000 spectroscopy in the 350-, and 450-micron telluric windows using NIST Transition-Edge Sensed (TES) bolometer arrays. We have expanded its capabilities to also cover the 200-micron window, and present first-light data for the new array from our 2019 observing campaign on the Atacama Pathfinder EXperiment (APEX) telescope. We also discuss the various enhancements we have implemented to improve observing efficiency and noise performance, including identifying and mitigating vibrations in hardware and improving the stability and robustness of the control software for the detector temperature. Furthermore, we have implemented several software routines to interface with the telescope control systems. These improvements, demonstrated during our recent observing campaign in Nov-Dec 2021, resulted in enhanced reliability and ease of operation, as well as increased sensitivity. A data-driven software pipeline, leveraging data from all 300 detectors on the array to remove common-mode noise, was implemented, and noise performance was further improved by robustly detecting unstable detectors and disabling them during observations.