Preliminary Results from an Interferometric Post-Coronagraph Wave Front Sensor

In high contrast imaging system, semi-static, non-common path wave front errors not sensed by the active wave front sensor in an adaptive optics system will ´leak´ around the coronagraph and lead to focal plane speckles that will mask exo-planets. Sensing and controlling these speckles is an absolute necessity for direct detection of planets from the ground. The next generation of AO systems that will enable direct detection of planets from the ground will become operational in the next couple of years. One of them, the Gemini planet imager, or GPI, 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. The current status of the GPI calibration system will be detailed, along with initial wavefront measurement results. This system promises a rich combination of interferometry and large optical systems in support of cutting edge science research.