Liger at W.M. Keck Observatory: imager structural analysis, fabrication, and characterization plan

TL;DR

This paper details the design, structural analysis, fabrication plan, and characterization procedures for the Liger imager, an adaptive optics instrument for the Keck Observatory, adapted from TMT's IRIS design.

Contribution

It introduces a new optical assembly design for the Liger imager, including structural analysis and a comprehensive fabrication and testing plan.

Findings

Structural analysis confirms design robustness.

Fabrication and assembly procedures outlined.

Characterization plan ensures instrument performance.

Abstract

Liger is an adaptive optics (AO) fed imager and integral field spectrograph (IFS) designed to take advantage of the Keck All-sky Precision Adaptive-optics (KAPA) upgrade to the Keck I telescope. Liger adapts the design of the InfraRed Imaging Spectrograph (IRIS) for the Thirty Meter Telescope (TMT) to Keck by implementing a new imager and re-imaging optics. The performance of the imager is critical as it sequentially feeds the spectrograph and contains essential components such as the pupil wheel, filter wheel, and pupil viewing camera. We present the design and structural analysis of the Liger imager optical assembly including static, modal, and thermal simulations. We present the fabrication as well as the full assembly and characterization plan. The imager will be assembled bench-top in a clean room utilizing a coordinate-measuring machine (CMM) for warm alignment. To ensure optimal performance, the imager will be characterized in a test cryostat before integration with the full Liger instrument. This comprehensive approach to characterization ensures the precision and reliability of the imager, enhancing the observational capabilities of Liger and W.M. Keck Observatory.