The Keck Wide Field Imager and Deployable Secondary Mirror

The Keck Wide Field Imager (KWFI) is a 1-degree field of view imager optimized to take advantage of the UV performance of the W.M. Keck Observatory located atop Mauna Kea in Hawaii. The project is an international collaboration between Swinburne University, ANU, AAO-Macquarie, Caltech, UC Observatories, and W.M. Keck Observatory. KWFI fills the 8m-class capability gap for deep, blue wide-field imaging and rapid-response follow-up necessary for many science cases, including cosmic reionization, transient astronomy at all wavelengths and messengers, and space mission main science aims. The instrument has a high-throughput, UV-sensitive design with an all-fused silica 4-lens element corrector system that operates from 300-1000 nm and achieves 0.4” 80% encircled energy diameter rms over the FOV within each photometric band. In 2022, we reported on the conceptual design of the imager that includes fast (~10 s) filter exchange of its 600 mm narrowband and broadband filters, fast (seconds) image processing and source identification, and CCD and CMOS detectors. More recently, the team has advanced the development of a Deployable Secondary Mirror (DM2), which will work with KWFI. The DM2 is a 1.4-meter lightweight, remotely deployable hexagonal secondary mirror to allow fast switching between KWFI and any Cassegrain or Nasmyth Instruments to enable rapid spectroscopic follow up of identified sources. We report here on the DM2 conceptual design, progress on the imager design, testing of the prototype filter exchange mechanism, and the interface of KWFI and the DM2 with the 30-year-old Keck Telescope.