Impact of Laser Guide Star facilities on neighbouring telescopes: The case of GTC, TMT, VLT and ELT lasers and the Cherenkov Telescope Array

Abstract

Powerful Laser Guide Star (LGS) systems are standard for the next-generation of extremely large telescopes. However, modern earth-based astronomy has gone through a process of concentration on few sites with exceptional sky quality, resulting in those becoming more and more crowded. The future LGS systems encounter hence an environment of surrounding astronomical installations, some of which observing with large fields-of-view. We derive formulae to calculate the impact of LGS light on the camera of a neighbouring telescope and the probabilities for a laser crossing the camera field-of-view to occur, and apply these to the specific case of the next very-high-energy gamma-ray observatory "Cherenkov Telescope Array" (CTA). Its southern part shall be constructed in a valley of the Cerro Armazones, Chile, close to the "Very Large Telescope" (VLT) and the "European Extremely Large Telescope" (ELT), while its northern part will be located at the "Observatorio del Roque de los Muchachos", on the Canary Island of La Palma, which also hosts the "Gran Telescopio de Canarias" (GTC) and serves as an optional site for the "Thirty Meter Telescope" (TMT), both employing LGS systems. Although finding the artificial star in the field-of-view of a CTA telescope will not disturb observations considerably, the laser beam crossing the field-of-view of a CTA telescope may be critical. We find no conflict expected for the ELT lasers, however, 1% (3%) of extra-galactic and 1% (5%) of galactic observations with the CTA may be affected by the GTC (TMT) LGS lasers, unless an enhanced version of a laser tracking control system gets implemented.

accepted for publication in MNRAS

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Cited by in corpus (5)

• Characterizing the aerosol atmosphere above the Observatorio del Roque de los Muchachos by analyzing seven years of data taken with an GaAsP HPD-readout, absolutely calibrated elastic LIDAR
• Laser Guide Star uplink beam: scattering and Raman emission measurements with the 10.4m Gran Telescopio CANARIAS
• A 1.8 m class pathfinder Raman LIDAR for the Northern Site of the Cherenkov Telescope Array Observatory -- Technical Design
• Photon return on-sky test for by-product Rayleigh plume of sodium laser guide star
• A 1.8 m class pathfinder Raman LIDAR for the Northern Site of the Cherenkov Telescope Array Observatory -- Performance