  The Wide-Field Infrared Transient Explorer (WINTER) is a new infrared
time-domain survey instrument which will be deployed on a dedicated 1 meter
robotic telescope at Palomar Observatory. WINTER will perform a seeing-limited
time domain survey of the infrared (IR) sky, with a particular emphasis on
identifying r-process material in binary neutron star (BNS) merger remnants
detected by LIGO. We describe the scientific goals and survey design of the
WINTER instrument. With a dedicated trigger and the ability to map the full
LIGO O4 positional error contour in the IR to a distance of 190 Mpc within four
hours, WINTER will be a powerful kilonova discovery engine and tool for
multi-messenger astrophysics investigations. In addition to follow-up
observations of merging binaries, WINTER will facilitate a wide range of
time-domain astronomical observations, all the while building up a deep coadded
image of the static infrared sky suitable for survey science.
  WINTER's custom camera features six commercial large-format Indium Gallium
Arsenide (InGaAs) sensors and a tiled optical system which covers a
$>$1-square-degree field of view with 90% fill factor. The instrument observes
in Y, J and a short-H (Hs) band tuned to the long-wave cutoff of the InGaAs
sensors, covering a wavelength range from 0.9 - 1.7 microns. We present the
design of the WINTER instrument and current progress towards final integration
at Palomar Observatory and commissioning planned for mid-2021.
