Paper 13100-262
Design and manufacture of athermalized optomechanical mounts for GRANCAIN, the infrared imaging instrument for GTC's adaptive optics
Abstract
GRANCAIN (GRAN CAmara INfrarroja) is a first-light imaging instrument in the infrared J, H and K bands that will be integrated into the adaptive optics focus of the Gran Telescopio de Canarias. The purpose of the instrument is to capture SWIR diffraction-limited images for a field of view of 22x22 arcsec. The instrument boasts a telecentric optical design with a collimator-camera configuration featuring a 2:1 magnification ratio. Housed within a 160-liter aluminum cryostat, its optical path includes a cold stop, a filter wheel, and a 4Mpx Hawaii-2 PACE Teledyne detector, meticulously engineered for operation at 77K. The optics is held in place by black anodized 6061-T6 aluminum supports. These mounts serve the critical purpose of precisely positioning the optics along the Z optical axis. The opto-mechanical frames contain adjustment elements in five degrees of freedom (all except the clock) for optical alignment and to compensate the thermal differential contractions that occur during the cooling-down process. Additionally, the lens-housing cell combines different geometries and materials with different coefficients of thermal expansion to avoid stresses on the glass so as not vary its relative position. A symmetrical and athermalized opto-mechanical design, free of residual stresses, helps to minimize the deviations of the optical axis and thus facilitates the iterative process of optical alignment in cryogenic conditions. A strict manufacturing and metrological control process were necessary in order to achieve the objectives for optimum image quality. The article contains a detailed description of the design, fabrication techniques, metrology, integration, alignment, and testing of the athermalized opto-mechanical elements.
Presenter
Instituto de Astrofísica de Canarias (Spain)
Telecommunication Engineer in 1992 at the Technical University of Madrid, Spain, and Master on Astrophysics in 2002 at the University of La Laguna, Spain. Joined the Instituto de Astrofísica de Canarias (IAC) in 1993 as Electronics Engineer for the Solar Correlation Tracker. In 1998 started as Project Manager in the IAC Technology Division, responsible for several contracts with ESA related with the development and operation of the Optical Ground Station, a 1m telescope for laser communications with satellites, laser propagation study through atmospheric turbulence, and space debris observation. In 2003 became responsible of the participation of IAC in the ELT Design Study, a contract with the European Commission leaded by ESO, for technological developments in wavefront control, adaptive optics and site characterization. In 2006 became Head of the Projects Department of IAC, Since 2014 leading the Adaptive Optics program of GTC.