Design and performance of a new generation, compact, low cost, very high Doppler precision and resolution optical spectrograph

Jian Ge; Bo Zhao; Scott Powell; Ji Wang; Adam Fletcher; Liang Chang; John Groot; Xiaoke Wan; Hali Jakeman; Derek Myers; Elliot Grafer; Jian Liu; Frank Varosi; Sidney Schofield; Alexandria Moore; Maria-Ines van Olphen; Jordan Katz; Rory Barnes

doi:10.1117/12.925795

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24 September 2012 Design and performance of a new generation, compact, low cost, very high Doppler precision and resolution optical spectrograph

Jian Ge, Bo Zhao, Scott Powell, Ji Wang, Adam Fletcher, Liang Chang, John Groot, Xiaoke Wan, Hali Jakeman, Derek Myers, Elliot Grafer, Jian Liu, Frank Varosi, Sidney Schofield, Alexandria Moore, Maria-Ines van Olphen, Jordan Katz, Rory Barnes

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Proceedings Volume 8446, Ground-based and Airborne Instrumentation for Astronomy IV; 84468R (2012) https://doi.org/10.1117/12.925795
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

Abstract

This paper is to report the design and performance of a very high Doppler precision cross-dispersed echelle spectrograph, EXtremely high Precision ExtrasolaR planet Tracker III (EXPERT-III), as part of a global Exoplanet Tracker (ET) network. The ET network is designed to hunt low mass planets, especially habitable rocky planets, around GKM dwarfs. It has an extremely high spectral resolution (EHR) mode of R=110,000 and a high resolution (HR) mode of R=56,000 and can simultaneously cover 0.38-0.9 μm with a 4kx4k back-illuminated Fairchild CCD detector with a single exposure. EXPERT-III is optimized for high throughput by using two-prisms cross-disperser and a large core diameter fiber (2 arcsec on sky, or 80 μm at f/4) to collect photons from the Kitt Peak National Observatory (KPNO) 2.1m telescope. The average overall detection efficiency is ~6% from above the atmosphere to the detector for the EHR Mode and about 11% for the HR mode. The extremely high spectral resolution in a compact design (the spectrograph dimension, 1.34x0.8x0.48 m) is realized by coupling the single input 80 μm telescope fiber into four 40 μm fibers and re-arranging the four small core diameter fibers into a linear fiber slit array (a one-to-four fiber image slicer). EXPERT-III is operated in a vacuum chamber with temperature controlled to ~2 milli-Kelvin rms for an extended period of time. The radial velocity (RV) drift is controlled to within 10 meters/second (m/s) over a month. EXPERT-III can reach a photon noise limited RV measurement precision of ~0.3 m/s for a V=8 mag GKM type dwarf with small rotation (vsini =2 km/s) in a 15 min exposure. EXPERT-III’s RV measurement uncertainties for bright stars are primarily limited by the Thorium-Argon (ThAr) calibration source (~0.5 m/s). EXPERT-III will serve as an excellent public accessible high resolution optical spectroscope facility at the KPNO 2.1m telescope.

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Jian Ge, Bo Zhao, Scott Powell, Ji Wang, Adam Fletcher, Liang Chang, John Groot, Xiaoke Wan, Hali Jakeman, Derek Myers, Elliot Grafer, Jian Liu, Frank Varosi, Sidney Schofield, Alexandria Moore, Maria-Ines van Olphen, Jordan Katz, and Rory Barnes "Design and performance of a new generation, compact, low cost, very high Doppler precision and resolution optical spectrograph", Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 84468R (24 September 2012); https://doi.org/10.1117/12.925795

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