Design and development of a digital micromirror device (DMD) based multi-object spectrograph (MOS) for the Indian spectroscopic and imaging space telescope (INSIST)

Abstract

The coming decade in astronomy focuses on large widefield imaging and spectroscopic surveys. No widefield imaging facility extends to the UV region, which represents an important window into a wide variety of astrophysical problems. Also, spectroscopy would be essential to understand the physical and chemical properties of several stars, star forming regions and galaxies. INSIST (the INdian Spectroscopic and Imaging Space Telescope) is a proposed future space UV mission to be able to observe in the UV (150nm-300nm), u (300nm-400nm) and g (400nm550nm) bands. Multi Object Spectrograph (MOS) is one of the key instruments proposed for INSIST to work in the UV band and efficiently obtain spectroscopic data for a large number of objects at a much shorter timescale. MOS is designed with a programmable reflective slit through a Digital Micromirror Device (DMD), which is an innovative opto-electro-mechanical component consisting of a 2-dimensional array of tiny mirrorlets that can be flipped to two orientations by command. DMD is to be used in a telescope in the UV region for MOS application for the first time in space. Hence, it is necessary to understand and study the functionality of DMD and its suitability to space telescopes. As part of this project, a spectrograph was designed with the DMD and set up on an optical bench in the laboratory. The performance and various parameters of the DMD were tested and the results are reported. Models were made for fabrication of an assembly to be tested at the J. C. Bhattacharya Telescope (JCBT) at Vainu Bappu Observatory in optical region.