Optical aspects of Near-Infrared Imager Spectrometer and Polarimeter instrument (NISP)

• Published in: arXiv.org 2020-12
• Main Authors: Rai, Archita, Ganesh, Shashikiran, Paul, Sukamal K, Kasarla, Prashanth K, Prajapati, Prachi V, Sarkar, Deekshya R, Singh, Alka, Patwal, Pitambar S, Adalja, Hitesh K L, Mathur, Satya N, Naik, Sachindra, Shah, Amish B, Baliyan, Kiran S
• Format: Article
• Language: English
• Subjects: Imaging; Infrared spectrometers; Linear polarization; Near infrared radiation; Polarimeters; Polarimetry; Prisms; Resolution; Spectroscopy; Spectrum analysis; Stokes parameters; Subsystems
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2012.08563

As a Near-IR instrument to PRL's upcoming 2.5 m telescope, NISP is designed indigeniously at PRL to serve as a multifaceted instrument. Optical, Mechanical and Electronics subsystems are being designed and developed in-house at PRL. It will consist of imaging, spectroscopy and imaging-polarimetry mode in the wavelength bands Y, J, H, Ks i.e. 0.8 - 2.5 micron. The detector is an 2K x 2K H2RG (MCT) array detector from Teledyne, which will give a large FOV of 10' x 10' in the imaging mode. Spectroscopic modes with resolving power of R ~ 3000, will be achieved using grisms. Spectroscopy will be available in single order and a cross-dispersed mode shall be planned for simultaneous spectra. The instrument enables multi-wavelength imaging-polarimetry using Wedged-Double Wollaston (WeDoWo) prisms to get single shot Stokes parameters (I, Q, U) for linear polarisation simultaneously, thus increasing the efficiency of polarisation measurements and reducing observation time.