Gemini [GPI] Gemini Planet Imager

The Gemini Planet Imager (GPI) will provide near InfraRed adaptive optics-corrected coronagraphic high contrast imaging to enable searches and characterization of extra-solar planets. NRC-HIA is part of a team comprised of several U.S. and Canadian groups who are currently in the build phase. Delivery of GPI to Gemini is currently scheduled for the early summer of 2011.

Project Lead: Les Saddlemyer

Exploitation of precision Doppler measurements has permitted astronomers to indirectly infer the existence of planets around stars in our galactic neighbourhood. Based on measuring the wobble in a star's velocity as the planet completes its orbit, this technique is unsuitable for planets at large separations from the star, with long orbital periods. As well, the indirect measurement provides no information on the composition of the planet.

Direct detection, or imaging, of planets would be a complementary technique well suited for the detection of planets at wider orbits. With the capability of imaging planets, we open up the ability to take spectra, and hence determine much more about the composition of the planet and its atmosphere.

Planets shine both by reflected light from the parent star and directly due to internal heat. From the distance we are from even nearby stars, planets appear very close to, and many millions of times fainter than their parent star. Somewhat akin to seeing a candle a couple of centimetres from a spotlight, a sophisticated instrument is required to separate the two.

Under the initial guidance of the Center for Adaptive Optics (CfAO), the GPI project is a collaboration to produce a powerful new instrument for the Gemini Telescope(s) with the following Institutes, led by Lawrence Livermore National Labs:

• LLNL: Lawrence Livermore National Labs (project lead)
• NRC-HIA: NRC Herzberg Institute of Astrophysics
• JPL: Jet Propulsion Laboratory
• UdeM: Université de Montréal
• INO: Institut National d'Optique
• UCLA's Infrared Instrumentation Laboratory
• UCSC: University of California , Santa Cruz
• UC Berkeley
• AMNH: American Museum of Natural History
• UCO/Lick: University of California Observatories

Technical overview

In order to overcome the large contrast between the star and planet there are a number of sub-systems that must work in concert. These include, in order, the following main components:

• A high-order adaptive optics (AO) system to correct the blurring effects of the atmosphere. This will reduce the apparent size of the star, which in a normal ground-based telescope would envelope the planet's light.
• A coronagraph to remove approximately 99% of the star light, while still allowing the majority of the planet's light to pass on through the system.
• A powerful "science instrument" system that can collect the relatively little light from the planet, distinguish it from the remaining scattered star light and not add instrumental noise or effects.
• Sophisticated post-processing software that can extract the planet's signature from the background.
• A real-time calibration system that monitors, and provides feedback to correct, any pseudo-static aberrations in the system. These slow, time varying aberrations would otherwise severely limt the ability to distinguish the faint planets from the background light.

Intrumentation

Initial deployment should take place in 2011 on the Gemini South telescope (Cerro Pachon, Chilean Andes), combining a 2000-actuator MEMS-based AO system, an apodized-pupil Lycot coronagraph, a precision infrared interferometer for real-time wavefront calibration at the nanometer level, and an infrared integral field spectrograph for detection and characterization of the target planets. GPI will be able to achieve Strehl ratios >0.9 at 1.65 microns and to observe a broad sample of science targets with I band magnitudes less than 8. In addition to planet detection, GPI will also be capable of polarimetric imaging of circumstellar dust disks, studies of evolved stars, and high-Strehl imaging spectroscopy of bright targets. In coming years, GPI may be used at the twin facility: Gemini North (Mauna Kea, Hawaii).

Current status

GPI is in the build phase at all sub-institutes. Integration will occur at the UCO/Lick Observatory shops located in the University of California, Santa Cruz.

A "Highlights" article discussing this project was published on the NRC web site in September 2006.

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Related Information

Institutes:

• NRC Herzberg Institute of Astrophysics