IBIS-TRE-01: Conceptual design of the IBIS 2.0 polarimetric unit

This document describes the polarimetric and optical design of the IBIS 2.0 polarimetric unit. Designed for the German Vacuum Tower Telescope, it will allow to acquire high resolution spectro-polarimetric data of the solar photosphere and chromosphere

The crystal ball, the spider and other stories: a journey around the test tower of the M4 adaptive mirror

M4 is the adaptive mirror of ELT, currently at its FDR. It is composed by 6 thin shell mirror segments, controlled by 5136 voice coil actuators. Before its installation at the telescope, it will be optically calibrated on a test facility (OTT) in Italy. The calibration includes the computation of the flattening command and the segments co-phasing, i.e. the correction of the differential piston amongst them. Given the large complexity of the deformable mirror and the very tight requests on the measurement accuracy, we set-up a risk-mitigation activity based on the laboratory demonstration of some key elements within the test tower. In this paper we present the results of the experimentation. We measured at nanometer level the interferometric cavity; we investigated how the interferometer reacts in presence of spider arms dividing the test mirror into separated islands; we integrated and tested a multi wavelength sensor to measure the inter-segment absolute differential piston; we aligned and tested for stability the pupil relaying optical system to be installed on the OTT. Such activity is performed in the AO laboratory at INAF-Arcetri in Italy, in preparation of the M4 optical calibration on the OTT, scheduled to start in 2020. The M4 project is led by the Italian consortium AdOptica under an ESO contract

A possible concept for the day-time calibration and co-phasing of the adaptive M4 mirror at the E-ELT telescope

The M4 unit is the deformable mirror providing the E-ELT with adaptive correction of the atmospheric turbulence. The mirror is segmented into 6 petals which are actively shaped by more than 5000 voice-coil actuators. They are controlled in close loop with internal metrology through co-located capacitive position sensors. INAF is involved in the optical calibration and verification of the M4 unit and designed the laboratory optical testbed In this paper, we present a possible auxiliary setup for the mirror calibration once installed at the telescope. The concept implements an on-demand, day-time, optical re-calibration of the mirror, to ensure the years-long term, high accuracy, high precision stability of the internal metrology, beyond the already remarkable intrinsic electronic stability of the M4 unit. The setup exploits the two focii of the quasi-elliptical M3 to create an optical cavity, with the interferometer placed at a Nasmyth focal station of the ELT and a retroreflector (or fiber source) at the M3 short focus to measure the M4 in double (or single) pass. The full monitoring of the M4 optical area allows to: calibrate the actuator influence functions to compute the segments piston tip/tilt commands with high precision; retrieve the flattening command to correct from the low and high order features generated by thermo-mechanical and electrical drifts; compute the phasing command to correct for the segments differential alignment and piston within the requested WF accuracy. The system offers a fast and effective optical maintenance facility for the M4U, without requiring an additional test tower and the mount/dismount down-time of the unit. In this work, we summarize the optical layout and the flattening and segments co-phasing strategy

Best practice for AO NIR observations with PISCES at LBT

The Adaptive Optics Scientific Working Group of the Large Binocular Telescope produced this document. It was distributed accompanying the LBT call for the Science Verification and Science Demonstration time in 2011 and 2012. It is also available following this link: https://wiki.lbto.org/AdaptiveOptics/AOGuidelinesThis document describes the best practices for imaging with PISCES+FLAO@LBT, emphasizing the main differences with common Near InfraRed (NIR) imaging. This document is based on the experience made on the first run of the PISCES+FLAO @ LBT commissioning that did not cover all the possible aspects

8s, a numerical simulator of the challenging optical calibration of the E-ELT adaptive mirror M4

8s stands for Optical Test TOwer Simulator (with 8 read as in italian 'otto'): it is a simulation tool for the optical calibration of the E-ELT deformable mirror M4 on its test facility. It has been developed to identify possible criticalities in the procedure, evaluate the solutions and estimate the sensitivity to environmental noise. The simulation system is composed by the finite elements model of the tower, the analytic influence functions of the actuators, the ray tracing propagation of the laser beam through the optical surfaces. The tool delivers simulated phasemaps of M4, associated with the current system status: actuator commands, optics alignment and position, beam vignetting, bench temperature and vibrations. It is possible to simulate a single step of the optical test of M4 by changing the system parameters according to a calibration procedure and collect the associated phasemap for performance evaluation. In this paper we will describe the simulation package and outline the proposed calibration procedure of M4

Toward large diffraction limited space telescopes with the Latt lightweight active primary

The design of large segmented mirrors, actively controlled both in shape and in differential piston, is one of the challenges space optics is facing, driven by the needs of the astronomical community

Astro MBSE: overview on requirement management approaches for astronomical instrumentation

Systems Engineering requires the involvement of different engineering disciplines: Software, Electronics, Mechanics (often nowadays together as Mechatronics), Optics etc. Astronomical Instrumentation is no exception to this. A critical point is the handling of the requirements, their tracing, flow down and the interaction with stakeholders (flow up) and subsystems (flow down) in order to have traceable and methodical evolution and management. In the Italian Astronomical Community, we are developing methodologies and tools to share the expertise in this field among the different projects. In this paper we will focus on the requirement management approach among different projects (ground and space based, …). The target and synthesis of tis work will be a support framework for the Requirement management of the Italian Astronomical Community (INAF) projects

Astro MBSE: model based system engineering synthesized for the Italian astronomical community

Systems Engineering requires the involvement of different engineering disciplines: Software, Electronics, Mechanics (often nowadays together as Mechatronics), Optics etc. Systems Engineering of Astronomical Instrumentation is no exception to this. A critical point is the handling of the different point of view introduced by these disciplines often related to different tools and cultures. Model Based Systems Engineering (MBSE) approach can help the Systems Engineer to always have a complete view of the full system. Moreover, in an ideal situation, all of the information resides in the model thus allowing different views of the System without having to resort to different sources of information, often outdated. In the real world, however, this does not happen because the different actors (Optical Designers, Mechanical Engineers, Astronomers etc.) should adopt the same language and this is clearly, at least nowadays and for the immediate future, close to impossible. In the Italian Astronomical Community, we are developing methodologies and tools to share the expertise in this field among the different projects. In this paper we present the status of this activity that aims to deliver to the community proper tools and template to enable a uniformed use of MBSE (friendly name Astro MBSE) among different projects (ground and space based, …). We will analyze here different software and different approaches. The target and synthesis of this work will be a support framework for the MBSE based system Engineering activity to the Italian Astronomical Community (INAF)

Preparing the E-ELT M4 optical test

The design of the interferometric test of the adaptive M4 Unit of E-ELT, a deformable six petals 2.4 m mirror, will be described. The actual baseline follows a macro-stitching approach, where each segment is separately flattened and co-phased to the other petals. The optical test setup for the single shell consists in a Newtonian system, with a 1.5 m parabolic mirror as main collimator. A 0.6 m reference flat mirror is foreseen to verify the alignment of the interferometric cavity. A Demonstration Prototype of the final M4 Unit, a 222 actuators, two shells deformable mirror, has been produced by Microgate and A.D.S. International. Results of the optical measurement campaign performed in INAF on the prototype mirror are reported