High-performance optics for astronomy
Reosc department has acquired expertise unique the world over in the design and manufacture of high-performance optics for astronomy: large monolithic mirrors, segmented mirrors for giant telescopes, lightweight mirrors, ultra-thin mirrors and field correctors.
Large monolithic mirrorsReosc is directly involved in astronomy advancements with the production of larger and more powerful collecting instruments.
Generally, ranging from one meter up to four meters in aperture, researchers have built and reached a new threshold, thanks to Reosc, with the four giant 8-meter telescopes of the Very Large Telescope (VLT) installed in Chile and the 2 American telescopes, Gemini, set up in Hawaii and Chile.
At the same time, due to Reosc’s capacity to produce more and more complex aspheric surfaces, the relative aperture of collecting mirrors has been reinforced, evolving from F/3 to F/2 then F/1.7 in the case of the Very Large Telescope (VLT). At present,Reosc is perfectly capable of developing F/1 apertures and lower.
In addition, the substrate thickness was put on a “diet”, allowing the telescopes to gain in mass via the active optics. Reosc has successfully integrated the requirement for substantial substrate flexibility into its know-how, in particular leading to a thickness of just 17.5 cm in the Very Large Telescope (VLT) mirrors. As a result, Reosc has produced a wide range of large-size optical equipment contributing to major developments in the field of astronomy, including the THEMIS solar telescope and Nishi Harima telescope mirrors, optics for the European Southern Observatory (ESO) telescope and the 8-m mirror for the Very Large Telescope (VLT).
Segmented mirrors for giant telescopesReosc masters the skills and expertise required for producing segmented mirrors adapted to giant telescopes.
For telescope apertures over 10 meters wide, the primary mirror requires the use of “segmented” technology – a technology mastered by Reosc in which each hexagonal segment must have exactly the same aspheric profile and curvature radius as the segments next to it, be polished with the utmost precision all the way to the edge and limit shape irregularities to only a few nanometers. Mirrors as gigantic and accurate as these will soon enable the observation of exoplanets around the stars closest to the solar system.
Lightweight mirrorsLightweight technology is crucial for secondary mirrors that are needed for stabilizing the stellar image perturbed by atmospheric turbulence. Precision polishing, high stiffness and low mass are essential. Sagem also holds a top rank in this field with the lightweight primary mirror for the Stratospheric Observatory For Ir Astronomy (SOFIA), the largest lightweight mirror in the world produced by machining honeycomb pockets in the glass-ceramic preform.
Ultra-thin mirrorsReosc has developed technology allowing the production of ultra-thin mirrors, 2-mm in thickness for a diameter ranging from 1 to 3 meters, adapted to very lightweight, low-mass active optics and adaptive optics in astronomy. Various demonstrators have been developed, in particular the meniscus for the Very Large Telescope M2 (VLT M2) adaptive mirrors and the M4’s glass shell prototype for the European Extremely Large Telescope (E-ELT).
Field correctorsReosc has produced several field correctors. This type of instrument offsets residual aberrations in telescopes and makes it possible to obtain high-quality images of a field several degrees in diameter. These correctors are formed by an array of large, often aspheric lenses assembled and aligned with precision in a support structure placed near the focal plane.