First Light Adaptive Optics System for Large Binocular Telescope
The paper describes the design of the single conjugate Adaptive Optics system to be installed on the LBT telescope. This system will be located in the Acquisition, Guiding and Wavefront sensor unit (AGW) mounted at the front bent Gregorian focus of LBT. Two innovative key features of this system are the Adaptive Secondary Mirror and the Pyramid Wavefront Sensor. The secondary provides 672 actuators wavefront correction available at the various foci of LBT. Due to the adaptive secondary mirror there is no need to optically conjugate the pupil on the deformable mirror. This allows having a very short sensor optical path made up using small dimension refractive optics. The overall AO system has a transmission of 70 % and fits in a rectangle of about 400x320mm. The pyramid sensor allows having different pupil sampling using on-chip binning of the detector. Main pupil samplings for the LBT system are 30x30, 15x15 and 10x10. Reference star acquisition is obtained moving the wavefront sensor unit in a field of view of 3x2 arcmin. Computer simulations of the overall system performance show the good correction achievable in J, H, and K. In particular, in our configuration, the limiting magnitude of pyramid sensor results more than one magnitude fainter with respect to ShackHartmann sensor. This feature directly translates in an increased sky coverage that is, in K band, about doubled with respect to the same AO system using a Shack-Hartmann sensor.
LBT-AdOpt control software
The LBT-AdOpt subsystem is a complex machine which includes several software controlled parts. It is essentially divided into two parts: a real-time loop which implements the actual adaptive optics control loop, from the wavefront sensor to the deformable secondary mirror, and a supervisor which performs a number of coordination and diagnostics tasks. The coordination and diagnostics task are essential for the proper operation of the system both as an aid for the preparation of observations and because only a continuous monitoring of dynamic system parameters can guarantee optimal performances and system safety during the operation. In the paper we describe the overall software architecture of the LBT-AdOpt supervisor and we discuss the functionalities required for a proper operation.
Prediction of net pressure on pressure equalized cavities
Abstract A numerical model has been developed for prediction of net pressure on pressure equalized cavities. The results based on this model show good agreement with those obtained from mock-up tests. Parametric studies verify that reductions in cladding load are possible, with proper design of curtain walls.