An Interferometric Wave Front Sensor for Measuring Post-Coronagraph Errors on Large Optical Telescopes

The Gemini Planet Imager (GPI) [B.Macintosh et al.], now in the early stages of development, is a ground-based extreme adaptive optics system with an advanced coronagraphic system and integral-field spectrometer. At commissioning in early 2011, it will be deployed on one of the twin eight meter Gemini Telescopes. This powerful instrument, which works at a science wavelength in the near-infrared, will enable the direct detection and characterization of self-luminous Jupiter-class planets from the ground. Semi-static and non-common path wave front errors that are not sensed by the active wave front sensor in the adaptive optics system will lead to a focal plane speckle pattern that will mask exo-planets. The GPI Instrument will incorporate an interferometric wave front sensor, designed and developed at JPL, which will measure these errors. This talk will emphasis this novel sensor and describes how it is used to measure the non-common path amplitude and phase errors in the system that would otherwise limit the achievable contrast. We will describe the system error budget as well as simulations that model the system performance. Finally, we will also discuss the status of our laboratory testbed that is designed to test the fundamental principles of post-coronagraph wave front sensing. This system promises a rich combination of interferometry and large optical systems in support of cutting edge science research.