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Palacký University
05-29-2015, 12:52, Age: 4 y.

Cameras and Telescope Mirrors for Next Generation Observatories

By: Martina Šaradínová

A segment of the mirror in a SST - small size telescope - made for the CTA project.

Their construction has not even begun, yet they already employ hundreds of experts from all around the world, including Olomouc. These are the observatories that will be built on both hemispheres by the international consortium CTA (Cherenkov Telescope Array). One of its members is the Joint Laboratory of Optics (JLO), run by Palacký University and the Physical Institute of the Academy of Sciences of the Czech Republic. Olomouc opticians develop unique all-sky cameras and special mirrors for telescopes. Thanks to the top-notch equipment in the Regional Centre of Advanced Technologies and Materials (RCPTM), Olomouc experts have participated not only in the selection of the location for the observatories, but also have been testing rival technologies.

The next-generation surface science facility is a follow-up on existing projects in Namibia, the USA, and the Canary Islands; its purpose is to observe cosmic gamma rays. It should enable the astrophysicists to investigate the high-energy universe more profoundly. Unlike existing observatories, it will cover the much larger energy spectrum of gamma photons, and thanks to better angular resolution, it will be able to measure the potential source of radiation more accurately. It is expected to contribute to better understanding of the mechanisms of acceleration of these high-energy particles.

Scientists as arbiters

The Olomouc team joined the project in 2012, also due to their previous experience in the project of the Pierre Auger observatory in Argentina. The all-sky cameras developed in collaboration with the Physical Institute of the Academy of Sciences and RCPTM monitored cloud cover in the night sky.

“Clear sky is crucial for observatories, so we have to find a place with the highest number of cloudless nights. Our measurements, subsequent analysis and data assessment were among the factors taken into consideration during the selection of the ideal location. We have developed new software that automatically assesses our measurements,” said Miroslav Hrabovský, the director of the research programme at JLO and RCPTM. According to him, the best conditions for an observatory in the northern hemisphere are in Namibia and then Chile. The northern hemisphere candidates include locations in Mexico, the Canary Islands, and the USA. The final decision as to where the telescopes will be located has not yet been made.

Scientists use astrometry during cloud monitoring. Consulting star catalogues, they look for concrete stars on the images, and if they cannot see them, they are either shrouded by clouds or blocked by ice or snow in front of the camera.

Next generation cameras

The cameras made in Olomouc will be used in the new observatory for the whole time of its existence.

“We have been developing a new camera now, one that should monitor the cloud cover as well as the direction of cloud movement. The data will be used to decide what sources will be used for observation. Our goal is to develop fully automatic systems, unprecedented in any observatory in the world,” said the scientist Dušan Mandát. The new generation of cameras is more sophisticated, with better optics, detector, and chip cooling.

“The analysis will become more complex, so we’re preparing new software that must be incorporated into the operating system of the observatory. Everything must be in mutual communication,” Mandát added. The systems must also be able to work at various temperatures, between plus 30 degrees to minus 25 degrees Celsius.

Mirrors like a football

Another contribution of Olomouc opticians to the international project involves the preparation and testing of telescope mirrors. Again, they can make good use of their abundant previous experience, having developed mirrors for fluorescence telescopes in the observatory in Argentina. In the planned CTA observatory, telescopes of several sizes will peer into the universe. The mirrors made in Haná will be used for the smallest ones. “However, the segments used in these telescopes are larger than those we have been producing,” said Mandát, demonstrating the relativity of the attribute “small”. The telescope can be simply described as a spherical cap comprised of hexagons – similar to a football. The smallest telescopes will be four metres in diameter, containing twenty hexagonal segments.

Thanks to new devices at RCPTM, local scientists are able to develop their own ultra-light mirrors as well as test all types that hope to qualify for the observatory. “We monitor a large number of parameters, such as optical properties, but also working life, abrasion, and resistance to rain, bird excrement, and changes in temperature. The telescopes will stand in the open and must resist adverse weather conditions. It would be extremely costly to roof them. “All kinds of samples arrive, and we test them. The data will show which mirrors should be used. Our ambition is, of course, to succeed with our own production,” Hrabovský confirmed.

Cameras and mirrors are developed exclusively for each project and according to specific requirements. “On the other hand, each of our special products has more general impact and can be used elsewhere,” Hrabovský stated.

Olomouc scientists should not worry about being not busy enough in the years to come. After solving the riddle of where the new CTA observatories will be located, their construction should not be delayed. Also, the observatories will commence their mission gradually, and this sort of facility will function for decades.

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Last update: 19. 09. 2012, Vladimír Kubák