The Wide-Field Infrared Transient Explorer (WINTER) is a new time-domain instrument which will perform a seeing-limited survey of the near-infrared sky. I will present the design and science goals of the WINTER instrument, which will be deployed on a dedicated 1-meter robotic telescope at Palomar Observatory. Among the many near-infrared targets of interest, WINTER is principally designed for follow-up of kilonovae from binary neutron star and neutron star-black hole mergers detected in gravitational waves. WINTER will be sensitive to kilonovae with 90% localization areas smaller than 150 (450) square degrees out to a distance of 350 (200) Mpc. In addition to kilonova follow-up, WINTER will conduct a wide range of time-domain surveys to a depth of J=21 magnitudes, building up a deep co-added image of the near-infrared sky and studying near-infrared transients including supernovae, tidal disruption events, and transiting exoplanets around low mass stars. WINTER���s custom camera combines six commercial large-format Indium Gallium Arsenide (InGaAs) sensors, observing in Y, J, and a short-H (Hs) band filters (0.9-1.7 microns), and employs a novel tiled optical design to cover a >1 degree squared field of view with 90% fill factor. I will include updates on the final integration of the WINTER instrument and commissioning at Palomar Observatory.

{"references": ["Lourie, N. P. et al. (2020) The wide-field infrared transient explorer (WINTER), in [Proc. SPIE ],114479K", "Frostig, D. et al. (2021). An Infrared Search for Kilonovae with the WINTER Telescope. I. Binary Neutron Star Mergers arXiv:2110.01622", "Frostig, D. et al. (2020) Design requirements for the wide-field infrared transient explorer (WINTER), in [Proc. SPIE ],11447(113) (2020)", "Hinrichsen, E. et al. (2020) Opto-mechanical mounting design of the wide-field infrared transient explorer (WINTER) \"fly's eye\" camera lenses, in [Proc. SPIE ],11447(115)", "Malonis, A. et al. (2020) Detector architecture of the wide-field infrared transient explorer (WINTER) InGaAs camera in [Proc. SPIE ],11454(105)"]}

WINTER's construction is made possible by the National Science Foundation under MRI grant number AST-1828470. We also acknowledge significant support for WINTER from the California Institute of Technology, the Caltech Optical Observatories, the Bruno Rossi Fund of the MIT Kavli Institute for Astrophysics and Space Research, and the MIT Department of Physics and School of Science.