Survey of airborne particle density and the aging of mirror coatings in the open air at the VLT Observatory

Paul Giordano; Marc S. Sarazin

doi:10.1117/12.176156

1 June 1994 Survey of airborne particle density and the aging of mirror coatings in the open air at the VLT Observatory

Paul Giordano, Marc S. Sarazin

Proceedings Volume 2199, Advanced Technology Optical Telescopes V; (1994) https://doi.org/10.1117/12.176156
Event: 1994 Symposium on Astronomical Telescopes and Instrumentation for the 21st Century, 1994, Kailua, Kona, HI, United States

Abstract

A long term survey of airborne particles was initiated in 1992 at the VLT Observatory of Cerro Paranal to establish the cleanliness of the telescope area before the start of construction work. The results presented in this paper shows large variations with time of the density of inhalable particles (< 10 micrometers ), and a very low density of the larger aerosols when compared to clean room industrial standards. In parallel with the aerosol survey, an analysis of the damage caused to mirror coatings was conducted by periodically exposing sets of mirrors outdoors at 10 m above ground level for periods of two weeks. A follow-up of the evolution: with time and meteorological conditions of the reflectivity, diffusion and scattering coefficients gives insights on mirror maintenance requirements in modern telescopes using natural air flushing to right local seeing. From the study of damages caused during wind storms, some new constraints on operational limits are discussed, in particular with regards to the protection of an unbaffled secondary mirror.

Citation Download Citation

Paul Giordano and Marc S. Sarazin "Survey of airborne particle density and the aging of mirror coatings in the open air at the VLT Observatory", Proc. SPIE 2199, Advanced Technology Optical Telescopes V, (1 June 1994); https://doi.org/10.1117/12.176156

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