Gemini planet imager observational calibration XIII: Wavelength calibration improvements, stability, and nonlinearity

Schuyler G. Wolff, Kimberly Ward-Duong, Joe Zalesky, Alex Z. Greenbaum, Marshall D. Perrin, James Graham

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations


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.

Original languageEnglish (US)
Title of host publicationGround-Based and Airborne Instrumentation for Astronomy VI
EditorsLuc Simard, Christopher J. Evans, Hideki Takami
ISBN (Electronic)9781510601956
StatePublished - 2016
Externally publishedYes
EventGround-Based and Airborne Instrumentation for Astronomy VI - Edinburgh, United Kingdom
Duration: Jun 26 2016Jun 30 2016

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


OtherGround-Based and Airborne Instrumentation for Astronomy VI
Country/TerritoryUnited Kingdom


  • GPI
  • Gemini Planet Imager
  • Integral Field Spectrograph
  • Wavelength Calibration

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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