On-instrument wavefront sensor design for the TMT infrared imaging spectrograph (IRIS) update

TL;DR

This paper discusses the preliminary design and prototyping of the on-instrument wavefront sensor for the IRIS instrument on the TMT, focusing on its components, accuracy, and optical considerations.

Contribution

It presents the initial design and prototyping efforts for the OIWFS, including the probe arm accuracy and optical component review for the TMT IRIS instrument.

Findings

Prototype of the probe arm developed and tested.

Design considerations for field de-rotation implemented.

Optical glass options for atmospheric dispersion correction reviewed.

Abstract

The first light instrument on the Thirty Meter Telescope (TMT) project will be the InfraRed Imaging Spectrograph (IRIS). IRIS will be mounted on a bottom port of the facility AO instrument NFIRAOS. IRIS will report guiding information to the NFIRAOS through the On-Instrument Wavefront Sensor (OIWFS) that is part of IRIS. This will be in a self-contained compartment of IRIS and will provide three deployable wavefront sensor probe arms. This entire unit will be rotated to provide field de-rotation. Currently in our preliminary design stage our efforts have included: prototyping of the probe arm to determine the accuracy of this critical component, handling cart design and reviewing different types of glass for the atmospheric dispersion.