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Published September 26, 2013 | Published
Book Section - Chapter Open

Precision near-infrared radial velocity instrumentation II: noncircular core fiber scrambler

Abstract

We have built and commissioned a prototype agitated non-circular core ber scrambler for precision spectroscopic radial velocity measurements in the near-infrared H band. We have collected the rst on-sky performance and modal noise tests of these novel bers in the near-infrared at H and K bands using the CSHELL spectrograph at the NASA InfraRed Telescope Facility (IRTF). We discuss the design behind our novel reverse injection of a red laser for co-alignment of star-light with the ber tip via a corneWe have built and commissioned a prototype agitated non-circular core fiber scrambler for precision spectroscopic radial velocity measurements in the near-infrared H band. We have collected the first on-sky performance and modal noise tests of these novel fibers in the near-infrared at H and K bands using the CSHELL spectrograph at the NASA InfraRed Telescope Facility (IRTF). We discuss the design behind our novel reverse injection of a red laser for co-alignment of star-light with the fiber tip via a corner cube and visible camera. We summarize the practical details involved in the construction of the fiber scrambler, and the mechanical agitation of the fiber at the telescope. We present radial velocity measurements of a bright standard star taken with and without the fiber scrambler to quantify the relative improvement in the obtainable blaze function stability, the line spread function stability, and the resulting radial velocity precision. We assess the feasibility of applying this illumination stabilization technique to the next generation of near-infrared spectrographs such as iSHELL on IRTF and an upgraded NIRSPEC at Keck. Our results may also be applied in the visible for smaller core diameter fibers where Fiber modal noise is a significant factor, such as behind an adaptive optics system or on a small < 1 meter class telescope such as is being pursued by the MINERVA and LCOGT collaborations.r cube and visible camera. We summarize the practical details involved in the construction of the ber scrambler, and the mechanical agitation of the ber at the telescope. We present radial velocity measurements of a bright standard star taken with and without the ber scrambler to quantify the relative improvement in the obtainable blaze function stability, the line spread function stability, and the resulting radial velocity precision. We assess the feasibility of applying this illumination stabilization technique to the next generation of near-infrared spectrographs such as iSHELL on IRTF and an upgraded NIRSPEC at Keck. Our results may also be applied in the visible for smaller core diameter bers where ber modal noise is a signi cant factor, such as behind an adaptive optics system or on a small < 1 meter class telescope such as is being pursued by the MINERVA and LCOGT collaborations.

Additional Information

© 2013 Society of Photo-Optical Instrumentation Engineers (SPIE). Peter Plavchan would like acknowledge Wes Traub and Stephen Unwin for seed funding provided by the JPL Center for Exoplanet Science and NASA Exoplanet Science Institute, as well as JPL Research and Technology Development grant in FY13. G. Anglada-Escudé would like to acknowledge the Carnegie Postdoctoral Fellowship Program and the support provided by the NASA Astrobiology Institute grant NNA09DA81A. Part of the research at the Jet Propulsion Laboratory (JPL) and California Institute of Technology was performed under contracts with National Aeronautics and Space Administration. We would like to thank Steve Osterman (U. of Colorado) for their valuable discussions. We also thank John Rayner, Morgan Bonnet, George Koenig, Kars Bergknut and Alan Tokunaga from IfA/Hawaii for their support during the fiber scrambler design reviews, integration and commissioning.

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