WINTER

The WINTER 1 meter telescope is a dedicated Planewave PW1000 CDK telescope, with custom modifications to optimize for infrared throughput on the corrector optics. It operates exclusively in a robotic, queue-scheduled observing mode with an API for realtime handling and observing of target-of-opportunity observations. Observing shedules are produced automatically each day, based on a configurable architecture for optimizing multiple surveys. While the telescope has extremely fast slew rates, typical observing overheads are dominated by dome moves.

a : WINTER camera before installation with covers removed to reveal tiled optics and densely packed focal planes.
b : Image of the bonded field lens array, the first optical element in the camera which slices the image into the 6 individual channels.
c, e : WINTER camera installed on the 1-m telescope with its rotary liquid cooling and cable management system.
d : Photograph of one of the WINTER packaged FPAs installed on its kinematically-mounted thermal block.
f : Drone's-eye view of WINTER telescope in its dome at the foot of the Palomar 200" telescope.

The current camera on the WINTER telescope is the WINTER (Wide-field Infrared Transient Explorer) infrared camera. This camera was commissioned in June 2023. It features six 1920 x 1080 pixel indium gallium arsenide (InGaAs) shortwave infrared sensors, sensitive from 900 - 1700 nm. A custom image slicer reimages a 1 x 1 degree field of view onto these six detectors, with each sensor having its own set of reimaging lenses. This configuration produces individual images for each sensor, and the primary output data product is a six-layer multiextension FITS file. Individual sensors achieve somewhat different depths/FWHM due to variations in detector performance and optical alignment between channels. The WINTER sensors are based on a CMOS readout architecture allowing significant increases in readout speed compared to CCDs. As WINTER transitions from commissioning to early survey operations, observers should expect higher rates of interrupts, engineering-related downtime, and changes to achieved performance than legacy facility instruments.

Left : Raw WINTER mosaic image showing the 2x3 layout to fill the full 1.14 square degree FoV. Large areas of hot pixels are from ROIC defects causing blooming glow spots.
Center : Sample zoomed in ROI from Port C showing the raw (top) and a processed image after dark/flat-correction and sky subtraction revealing many more stars.
Right : Sample transient detection of a 16 magnitude supernova using the WINTER data reduction pipeline, showing the WINTER image (top, using sensor Port C), a UKIRT J-band reference (center), and the difference image (bottom).

Specs

Telescope	WINTER 1-m / 39-inch Planewave CDK
Field of View	1.14 square degree (1.02 sq. deg with outages)
Detectors	6 Boards (Star A/B/C, Port A/B/C): Teledyne FLIR AP1020 Rev B0 1920 x 1080 pixels
Pixel Size	15 micron
Pixel Scale	1.11"/pixel
Delivered Image Quality	2.3-3.6" FWHM (Range of Medians; Varies by Board)
Exposure Time (Fiducial)	120s x 8 dithers
Readout Time (Typ.)	<1 sec
Median Overhead for Slew and Settle Time	5s (Adjacent), 70s (Large Slews)
Median Single Visit Depth (J-band)	18.5 (Port A), 18.5 (Port B), 19.3 (Port C), 18.6 (Star A), 17.6 (Star B), 18.5 (Star C)
Filters	MKO Y, J, Hs (shortened MKO H-band with 1.7 micron cutoff)