Next generation low resolution Wide Field Multi-Object Optical Spectrometer for W.M. Keck Observatory

Year: 2024

DOI: 10.1117/12.3020284

We present a concept design for a next generation low resolution, wide-field, optical imaging spectrometer intended to continue the legacy of LRIS as the premier workhorse optical spectrometer on the Keck I telescope, which we notionally call LRIS-2. The original LRIS continues to be used an average of more than 100 nights per year while maintaining a remarkably high publication rate, neither of which shows any signs of diminishing with time. Nevertheless, LRIS was commissioned ∼30 years ago, and its opto-mechanical design and aging mechanisms preclude further improvements in its stability and reliability. This paper presents the conceptual design of a state-of-the-art instrument combining the core capabilities and scientific versatility of LRIS with substantial improvements in throughput, image quality, stability, and on-sky efficiency. In this paper, we present a concept for a versatile imaging spectrometer with an on-axis field of view of 10′×5′ in two simultaneous wavelength channels that together cover 3100 – 10,300Å at R∼1500 in a single exposure, with a multiplex factor of 70. The optical design delivers total spectroscopic throughput close to 60%, a gain over the current LRIS of 30-100%. The design is able to benefit from significant engineering heritage from LRIS-B, KCWI, KCRM, and TMT-WFOS projects.