The WINTER Observatory: A One-Degree InGaAs Survey Camera to study the Transient Infrared Sky

TL;DR

The WINTER Observatory is a new one-degree infrared survey camera using InGaAs sensors, enabling rapid, wide-field near-infrared sky observations for transient detection and technology demonstration.

Contribution

It introduces a novel wide-field InGaAs-based infrared camera with a unique optical design for time-domain sky surveys and demonstrates its early scientific capabilities.

Findings

Surveyed the sky nightly to median depth of J_AB=18.5 mag

Successfully detected and characterized infrared transients

Validated the performance of InGaAs sensors for wide-field infrared astronomy

Abstract

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.