The Wide-field Infrared Transient Explorer (WINTER) is a near-infrared time-domain survey instrument operating on a dedicated 1-meter robotic telescope at Palomar Observatory. The project takes advantage of recent technology advances in time-domain astronomy, robotic telescopes, large-format sensors, and rapid data reduction and alert software for timely follow up of events. Since June of 2023, WINTER robotically surveys the sky each night to a median depth of J_AB = 18.5 mag, balancing a variety of science programs including searching for kilonovae from gravitational-wave alerts, blind surveys to study galactic and extragalactic transients and variables, and building up reference images of the near-infrared sky. The project also serves as a technology demonstration for new large-format Indium Gallium Arsenide (InGaAs) sensors for wide-field science in the near infrared without cryogenically cooled optics or detectors. WINTER's custom camera combines six InGaAs sensors with a novel tiled fly's-eye optical design to cover a >1 deg^2 field of view with 1 arcsecond pixels in the Y-, J-, and shortened-H-band filters (0.9 - 1.7 micron). This paper presents the design, performance, and early on-sky science of the WINTER observatory.
@article{arxiv.2512.16753,
title = {The WINTER Observatory: A One-Degree InGaAs Survey Camera to study the Transient Infrared Sky},
author = {Danielle Frostig and Nathan Lourie and Viraj Karambelkar and Mansi M. Kasliwal and Andrew Malonis and Robert A. Simcoe and Robert Stein and John W. Baker and Kevin Burdge and Rick Burruss and Curt Corcoran and Kishalay De and Gabor Furesz and Nicolae Ganciu and Kari Haworth and Carolyn M. Heffner and Erik Hinrichsen and Jill Juneau and Geoffrey Mo and Josiah Purdum and Sam Rose and Cruz Soto and Jeffry Zolkower},
journal= {arXiv preprint arXiv:2512.16753},
year = {2026}
}