Ocam is readied to photograph exoplanets

Posted by Emma Woollacott

Marseilles, France - The world's fastest and most sensitive astronomical camera is taking its first pictures.


Ocam was created through a collaborative effort between ESO and  the French Centre National de la Recherche Scientifique/Institut National des Sciences de l'Univers (CNRS/INSU. It can take 1,500 finely exposed images per second even when observing extremely faint objects, and has produced its first 240x240 pixel images.


“The performance of this breakthrough camera is without an equivalent anywhere in the world. The camera will enable great leaps forward in many areas of the study of the universe,” said Norbert Hubin, head of the Adaptive Optics department at ESO.


OCam will be part of the second-generation Very Large Telescope (VLT) instrument Sphere. To be installed in 2011, Sphere will take images of giant exoplanets orbiting nearby stars.


The Ocam camera


Adaptive optics techniques overcome the blurring effect of atmospheric turbulence, so that ground-based telescopes can produce images that are as sharp as those taken from space. Adaptive optics is based on real-time corrections many hundreds of times each second. The new generation instruments require these corrections to be done at an even higher rate, more than one thousand times a second, and this is where OCam comes in.


“The quality of the adaptive optics correction strongly depends on the speed of the camera and on its sensitivity,” said Philippe Feautrier, who coordinated the whole 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 - obviously not an option for astronomical cameras.


Because of imperfect operation of any physical electronic devices, a CCD camera suffers from so-called readout noise. OCam 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 Marseilles, 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,” said Hubin.


 

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