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Proceedings Paper

Gemini planet imager observational calibration XIII: wavelength calibration improvements, stability, and nonlinearity
Author(s): Schuyler G. Wolff; Kimberly Ward-Duong; Joe Zalesky; Alex Z. Greenbaum; Marshall D. Perrin; James Graham
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Paper Abstract

We present improvements to the wavelength calibration for the lenslet-based Integral Field Spectrograph (IFS), that serves as the science instrument for the Gemini Planet Imager (GPI). The GPI IFS features a 2.7”×2.7” field of view and a 190 x 190 lenslet array (14.1 mas/lenslet) with spectral resolving power ranging from R ~ 35 to 78. A unique wavelength solution is determined for each lenslet characterized by a two-dimensional position, an n-dimensional polynomial describing the spectral dispersion, and the rotation of the spectrum with respect to the detector axis. We investigate the non-linearity of the spectral dispersion across all Y, J, H, and K bands through both on-sky arc lamp images and simulated IFS images using a model of the optical path. Additionally, the 10-hole non-redundant masking mode on GPI provides an alternative measure of wavelength dispersion within a datacube by cross-correlating reference PSFs with science images. This approach can be used to confirm deviations from linear dispersion in the reduced datacubes. We find that the inclusion of a quadratic term provides a factor of 10 improvement in wavelength solution accuracy over the linear solution and is necessary to achieve uncertainties of a few hundredths of a pixel in J band to a few thousands of a pixel in the K bands. This corresponds to a wavelength uncertainty of ~ 0.2 nm across all filters.

Paper Details

Date Published: 9 August 2016
PDF: 10 pages
Proc. SPIE 9908, Ground-based and Airborne Instrumentation for Astronomy VI, 990838 (9 August 2016); doi: 10.1117/12.2233644
Show Author Affiliations
Schuyler G. Wolff, Johns Hopkins Univ. (United States)
Kimberly Ward-Duong, Arizona State Univ. (United States)
Joe Zalesky, Univ. of California, Berkeley (United States)
Alex Z. Greenbaum, Johns Hopkins Univ. (United States)
Marshall D. Perrin, Space Telescope Science Institute (United States)
James Graham, Univ. of California, Berkeley (United States)

Published in SPIE Proceedings Vol. 9908:
Ground-based and Airborne Instrumentation for Astronomy VI
Christopher J. Evans; Luc Simard; Hideki Takami, Editor(s)

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