Design and Performance of the Upgraded Mid-InfraRed Spectrometer and Imager (MIRSI) on the NASA Infrared Telescope Facility

TL;DR

The paper details the redesign and upgraded performance of MIRSI, a mid-infrared spectrometer and imager at NASA's IRTF, featuring a new cooling system, electronics, and optical enhancements for improved observational efficiency.

Contribution

It introduces a new cryogen-free cooling system and upgraded electronics and optics, enhancing MIRSI's operational readiness and observational capabilities at the IRTF.

Findings

Successful implementation of a closed-cycle cooler for MIRSI.

Enhanced detector readout electronics and optical camera system.

Improved instrument stability and observational efficiency.

Abstract

We describe the new design and current performance of the Mid-InfraRed Spectrometer and Imager (MIRSI) on the NASA Infrared Telescope Facility (IRTF). The system has been converted from a liquid nitrogen/liquid helium cryogen system to one that uses a closed-cycle cooler, which allows it to be kept on the telescope at operating temperature and available for observing on short notice, requiring less effort by the telescope operators and day crew to maintain operating temperature. Several other enhancements have been completed, including new detector readout electronics, an IRTF-style standard instrument user interface, new stepper motor driver electronics, and an optical camera that views the same field as the mid-IR instrument using a cold dichroic mirror, allowing for guiding and/or simultaneous optical imaging. The instrument performance is presented, both with an engineering-grade array used from 2021-2023, and a science-grade array installed in the fall of 2023. Some sample astronomical results are also shown. The upgraded MIRSI is a facility instrument at the IRTF available to all users.