Preliminary optical design of PANIC, a wide-field infrared camera for CAHA

TL;DR

This paper details the initial optical design of PANIC, a wide-field infrared camera for the Calar Alto telescope, emphasizing its optical configuration, material choices, and performance considerations for multiple infrared bands.

Contribution

It introduces a novel optical design for PANIC that optimizes throughput, minimizes aberrations, and integrates narrow band filters without a collimated stage.

Findings

Design achieves a 31.9 arcmin field of view.

Optical performance meets specified criteria with error correction.

Design demonstrates flexibility for use on a 3.5m telescope.

Abstract

In this paper, we present the preliminary optical design of PANIC (PAnoramic Near Infrared camera for Calar Alto), a wide-field infrared imager for the Calar Alto 2.2 m telescope. The camera optical design is a folded single optical train that images the sky onto the focal plane with a plate scale of 0.45 arcsec per 18 micron pixel. A mosaic of four Hawaii 2RG of 2k x 2k made by Teledyne is used as detector and will give a field of view of 31.9 arcmin x 31.9 arcmin. This cryogenic instrument has been optimized for the Y, J, H and K bands. Special care has been taken in the selection of the standard IR materials used for the optics in order to maximize the instrument throughput and to include the z band. The main challenges of this design are: to produce a well defined internal pupil which allows reducing the thermal background by a cryogenic pupil stop; the correction of off-axis aberrations due to the large field available; the correction of chromatic aberration because of the wide spectral coverage; and the capability of introduction of narrow band filters (~1%) in the system minimizing the degradation in the filter passband without a collimated stage in the camera. We show the optomechanical error budget and compensation strategy that allows our as built design to met the performances from an optical point of view. Finally, we demonstrate the flexibility of the design showing the performances of PANIC at the CAHA 3.5m telescope.