Cryogenics at the Extremely Large Telescope (ELT)

The European Southern Observatory (ESO) is building the Extremely Large Telescope (ELT), a 40-m class telescope to be installed on top of the 3046 m high mountain Cerro Armazones in the central part of Chile's Atacama Desert. Once being operational around 2025, the ELT will be the largest optical/near-infrared telescope in the world, gathering 13 times more light than the largest optical telescopes existing today. “The world's biggest eye on the sky” will vastly advance astrophysical knowledge by enabling detailed studies of planets around other stars, the first galaxies in the Universe, super-massive black holes, and the nature and distribution of dark matter and energy which dominate the Universe. Powerful facility instruments are under development that can deliver the science cases for the ELT. The first instrument roadmap is listing more than six scientific instruments, each of them in the 10 - 20 tons class. Three selected first-light instruments are currently in detailed design phase, a diffraction-limited near-infrared imager, a single-field near-infrared wide-band integral field spectrograph, and a mid-infrared imager and spectrometer. ... mehrWhile the telescope optics operates at ambient temperature, the instrument optics and in particular the detectors will be cooled to cryogenic temperatures down to 4 Kelvin. ESO is aiming to implement proven technology and commercial off-the-shelf components to build the cryogenic infrastructure for the ELT instruments. A combination of Liquid Nitrogen cooling and low-vibration cryo-coolers will be installed to provide the required temperature levels and cooling capacities. I will present a brief status of the ELT construction and the planned instruments, and will give an overview of the cryogenic concept.