CCD-based adaptive optics enable "world's fastest, most sensitive astronomical camera"

June 22, 2009--"The performance of this breakthrough camera is without an equivalent anywhere in the world," says Norbert Hubin of the European Southern Observatory (ESO; Garching, Germany). The camera, called Ocam, will be part of the second-generation very large telescope (VLT) instrument called SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research). "The camera will enable great leaps forward in many areas of the study of the Universe," he notes.

June 22, 2009--"The performance of this breakthrough camera is without an equivalent anywhere in the world," says Norbert Hubin head of the Adaptive Optics department at the European Southern Observatory (ESO; Garching, Germany). The camera, called Ocam, will be part of the second-generation very large telescope (VLT) instrument called SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research). "The camera will enable great leaps forward in many areas of the study of the Universe," Hubin notes.

Ground-based telescopes such as SPHERE suffer from the blurring effect induced by atmospheric turbulence. Adaptive optics, based on real-time corrections computed from images obtained by a special high-speed camera, overcome this drawback. The new generation instruments require these corrections to be done at more than one thousand times a second.

"The quality of the adaptive optics correction strongly depends on the speed of the camera and on its sensitivity," says Philippe Feautrier from the Laboratoire d'Astrophysique de Grenoble (LAOG; Grenoble, France), who coordinated the overall project. "But these are a priori contradictory requirements, as in general the faster a camera is, the less sensitive it is." This is why cameras normally used for very high frame-rate movies require extremely powerful illumination, which is of course not an option for astronomical cameras.

OCam and its CCD220 detector, developed by e2v technologies (Chelmsford, England), solve this dilemma, by being not only the fastest available, but also very sensitive, making a significant jump in performance for such cameras. Because of imperfect operation of any physical electronic devices, a CCD camera suffers from so-called readout noise. OCam reportedly has a readout noise ten times smaller than the detectors currently used on the VLT, making it much more sensitive and able to take pictures of the faintest of sources.

"Thanks to this technology, all the new generation instruments of ESO's Very Large Telescope will be able to produce the best possible images, with an unequalled sharpness," declares Jean-Luc Gach, from the Laboratoire d'Astrophysique de Marseille, France, who led the team that built the camera.

"Plans are now underway to develop the adaptive optics detectors required for ESO's planned 42-metre European Extremely Large Telescope, together with our research partners and the industry," says Hubin.

Using sensitive detectors developed in the UK, with a control system developed in France, with German and Spanish participation, OCam is truly an outcome of a European collaboration that will be widely used and commercially produced.

The three French laboratories involved are the Laboratoire d'Astrophysique de Marseille (LAM/INSU/CNRS, Université de Provence; Observatoire Astronomique de Marseille Provence), the Laboratoire d'Astrophysique de Grenoble (LAOG/INSU/CNRS, Université Joseph Fourier; Observatoire des Sciences de l'Univers de Grenoble), and the Observatoire de Haute Provence (OHP/INSU/CNRS; Observatoire Astronomique de Marseille Provence).

OCam and the CCD220 are the result of five years work, financed by the European commission, ESO and CNRS-INSU, within the OPTICON project of the 6th Research and Development Framework Programme of the European Union. The development of the CCD220 was supervised by ESO.

The corresponding OPTICON activity was led by the Laboratoire d'Astrophysique de Grenoble, France. The OCam camera was built by a team of French engineers from the Laboratoire d'Astrophysique de Marseille, the Laboratoire d'Astrophysique de Grenoble and the Observatoire de Haute Provence. In order to secure the continuation of this successful project a new OPTICON project started in June 2009 as part of the 7th Research and Development Framework Programme of the European Union with the same partners, with the aim of developing a detector and camera with even more powerful functionality for use with an artificial laser star. This development is necessary to ensure the image quality of the future 42-meter European Extremely Large Telescope.

ESO is an intergovernmental astronomy organization supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious program focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries.

For more information see the ESO website.

Posted by Barbara G. Goode, barbarag@pennwell.com, for Laser Focus World.

More in Optics