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Published September 14, 2011 | Published
Book Section - Chapter Open

Ten-fold spectral resolution boosting using TEDI at the Mt. Palomar NIR Triplespec spectrograph

Abstract

An optical technique called "interferometric spectral reconstruction" (ISR) is capable of increasing a spectrograph's resolution and stability by large factors, well beyond its classical limits. We have demonstrated a 6- to 11-fold increase in the Triplespec effective spectral resolution (R=2,700) to achieve R=16,000 at 4100 cm-^(1) to 30,000 at 9600 cm^(-1) by applying special Fourier processing to a series of exposures with different delays (optical path differences) taken with the TEDI interferometer and the near-infrared Triplespec spectrograph at the Mt. Palomar Observatory 200 inch telescope. The TEDI is an externally dispersed interferometer (EDI) used for Doppler radial velocity measurements on M-stars, and now also used for ISR. The resolution improvement is observed in both stellar and telluric features simultaneously over the entire spectrograph bandwidth (0.9-2.45 μm). By expanding the delay series, we anticipate achieving resolutions of R=45,000 or more. Since the delay is not continuously scanned, the technique is advantageous for measuring time-variable phenomena or in varying conditions (e.g. planetary fly-bys). The photon limited signal to noise ratio can be 100 times better than a classic Fourier Transform Spectrometer (FTS) due to the benefit of dispersion.

Additional Information

© 2011 SPIE. This material is based upon work supported by the National Science Foundation under Grant No. AST-0505366, AST-096064, NASA Grant NNX09AB38G, and by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Thanks to Ed Wishnow for molecular spectra calculations and valuable advice over the years. Thanks to Palomar Observatory and UC Berkeley Space Sciences staff including Mario Marckwordt, Michael Feuerstein, and Gregory Dalton. Thanks to Triplespec PI Terry Herter and Cornell staff Charles Henderson and Stephen Parshley. Travis Barman provided high-res model stellar spectrum used in TEDI performance simulations.

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