Mechanical aspects of Near-Infrared Imager Spectrometer and Polarimeter

TL;DR

This paper details the mechanical design and cryogenic system of the Near-Infrared Imager Spectrometer and Polarimeter (NISP) for a 2.5m telescope, focusing on its optical, mechanical, and thermal components.

Contribution

It provides a comprehensive description of the mechanical and cryogenic design aspects of NISP, a novel instrument for near-infrared astronomy.

Findings

Design of cryogenic support structures using GFRP

Implementation of two-layer thermal shielding

Use of magnet-reed switch for filter wheel positioning

Abstract

Near-infrared Imager Spectrometer and Polarimeter (NISP) is a camera, an intermediate resolution spectrograph and an imaging polarimeter being developed for upcoming 2.5m telescope of Physical Research Laboratory at Mount Abu, India. NISP is designed to work in the Near-IR (0.8-2.5 micron) using a H2RG detector. Collimator and camera lenses would transfer the image from the focal plane of the telescope to the detector plane. The entire optics, mechanical support structures, detector-SIDECAR assembly will be cooled to cryo-temperatures using an open cycle Liquid Nitrogen tank inside a vacuum Dewar. GFRP support structures would be used to isolate cryogenic system from the Dewar. Two layer thermal shielding would be used to reduce the radiative heat transfer. Molecular sieve (getter) would be used to enhance the vacuum level inside Dewar. Magnet-reedswitch combination are used for absolute positioning of filterwheels. Here we describe the mechanical aspects in detail.