Characterization of the Atmospheric Dispersion Corrector of the Gemini   Planet Imager
  An Atmospheric Dispersion Corrector (ADC) uses a double-prism arrangement to nullify the vertical chromatic dispersion introduced by the atmosphere at non-zero zenith distances. The ADC installed in the Gemini Planet Imager (GPI) was first tested in August 2012 while the instrument was in the laboratory. GPI was installed at the Gemini South telescope in August 2013 and first light occurred later that year on November 11th. In this paper, we give an overview of the characterizations and performance of this ADC unit obtained in the laboratory and on sky, as well as the structure of its control software. 
Pascale Hibon, Sandrine Thomas, Jennifer Dunn, Jenny Atwood, Les   Saddlemyer, Naru Sadakuni, Stephen Goodsell, Bruce Macint...
astro-ph.IM astro-ph.EP