High resolution infrared spectroscopy has been a major challenging task to accomplish in astronomy due to the enormous size and cost of IR spectrographs built with traditional gratings. A silicon immersion grating, due to its over three times high dispersion over a traditional reflective grating, offers a compact and low cost design of new generation IR high resolution spectrographs. Here we report the on-sky performance of the first silicon immersion grating spectrometer, called Florida IR Silicon immersion grating spectromeTer (FIRST), commissioned at the 2-meter Automatic Spectroscopic Telescope (AST) of Fairborn Observatory in Arizona in October 2013. The measured spectral resolution is R=50,000 with a 50 mm diameter spectrograph pupil and a blaze angle of 54.7 degree. The 1.4-1.8 m wavelength region (the Red channel) is completely covered in a single exposure with a 2kx2k H2RG IR array while the 0.8-1.35 μm region is nearly completely covered by the cross-dispersed echelle mode (the Blue channel) at R=50,000 in a single exposure. The instrument is operated in a high vacuum (about 1 micro torr) and cryogenic temperatures (the bench at 189K and the detector at 87K) and with a precise temperature control. It is primarily used for high precision Doppler measurements (~3 m/s) of low mass M dwarf stars for the identification and characterization of extrasolar planets. A plan for a high cadence and high precision survey of habitable super-Earths around ~150 nearby M dwarfs and a major upgrade with integral field unit low resolution spectroscopy are also introduced.

Date Published: 8 July 2014
PDF: 12 pages
Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 91471A (8 July 2014); doi: 10.1117/12.2057023

Published in SPIE Proceedings Vol. 9147:
Ground-based and Airborne Instrumentation for Astronomy V
Suzanne K. Ramsay; Ian S. McLean; Hideki Takami, Editor(s)