The Wide-Field Infrared Transient Explorer (WINTER): a new near-infrared time-domain survey

Abstract

The Wide-Field Infrared Transient Explorer (WINTER) is a new near-infrared observatory for time-domain astronomy, the study of the evolving night sky. The field has exploded in the last two decades at optical wavelengths, but complementary infrared efforts have been limited by available detector technologies. In this thesis, I present the design, build, and early operations of the new WINTER instrument, which was installed on a dedicated 1-meter robotic telescope at Palomar Observatory in June of 2023.

WINTER’s science goals include robotic follow-up of kilonovae from binary neutron star (BNS) and neutron-star black-hole (NSBH) mergers, surveys to study galactic and extragalactic transients and variables, and building up a deep coadded image of the near-infrared sky. The project also helped develop the world’s largest Indium Gallium Arsenide (InGaAs) detectors for cost-effective near-infrared astronomical imaging without cryogenic cooling. The custom camera combines six InGaAs detectors with a novel tiled fly’s-eye optical design to cover a >1 degree-squared field of view with a 90\% fill factor. WINTER observes in the Y-, J-, and shortened-H-band filters (0.9-1.7 microns), with a filter tray selecting one filter at a time.

The project is a collaboration between MIT and Caltech, with Caltech leading the data reduction pipeline and observatory site management and MIT leading the instrument and facility hardware and operations. This thesis touches upon all aspects of the instrument, highlighting the major subsystems I directed, including detailed instrument design and modeling, project requirements flowdown, kilonova follow-up science simulations, testing of new detectors alongside the development of custom readout firmware and software, stray-light analysis, robotic scheduling software, and on-sky early operations and science.

Since its installation in 2023, WINTER has been operating robotically each night, with ongoing work to improve the instrument. This thesis presents a snapshot of WINTER's progress as of April 2024, concluding with an update on its current performance and future directions for the project.