S. Esposito

First light AO system for LBT: toward on-sky operation

The paper is describing the present status of the LBT first light AO system. The system design started in January 2002 and is now approaching the final test in the Arcetri solar tower. Two key features of this single conjugate AO system are the use of an adaptive secondary mirror having 672 actuators and a pyramid wavefront sensor with a maximum sampling of 30x30 subapertures. The paper is reporting about the adaptive secondary mechanical electrical and optical integration, and the wavefront sensor unit integration and acceptance test. Finally some lab test of the AO system done using an adaptive secondary prototype with 45 actuators, the so called P45 are described. The aim of these test was to get an estimate of the system limiting magnitude and to demonstrate the feasibility of a new technique able to measure AO system interaction matrix in a shortest time and with higher SNR with respect to the classical interaction matrix measurement. We are planning to use such a technique to calibrate the AO system in Arcetri and later at the LBT telescope.

High SNR measurement of interaction matrix on-sky and in lab

The fundamental task of AO system calibration is the acquisition of the Interaction Matrix (IM). This task is usually performed in a laboratory or at the telescope using a reference fiber illuminating both deformable mirror and wavefront sensor. The problem of measuring the IM on a bright reference star has been attacked by some authors. The principal problem of this measurement is to achieve a high SNR when atmospheric turbulence is present. This is very difficult if sensor signals are simply time averaged to get rid of the turbulence effects. The paper presents a new technique to perform an on sky measurement of the IM with high SNR and reducing the overall measurement time by an order of magnitude. This technique can be very useful for AO systems using large size DMs like MMT, LBT and possibly VLT and OWL. In these cases fiber-based IM measurements require challenging optical set-up that in some cases, like for OWL, are unpractical to build. The technique is still relevant for classical small DM AO systems that could be calibrated on sky avoiding misregistration errors. Finally this technique is valuable for laboratory measurements when the IM of an AO system has to be measured with great accuracy against external disturbances like bench vibrations, local turbulence effects and so on. Again IM measurement SNR is increased and the overall measurement time can be significantly reduced. The paper will introduce and detail the technique physical principle and quantify with numerical simulations the SNR improvement achieved using this technique. Finally laboratory results obtained during the test of the LBT AO system prototype are given and compared to simulations.

SOUL: The Single conjugated adaptive Optics Upgrade for LBT

We present here SOUL: the Single conjugated adaptive Optics Upgrade for LBT. Soul will upgrade the wavefront sensors replacing the existing CCD detector with an EMCCD camera and the rest of the system in order to enable the closed loop operations at a faster cycle rate and with higher number of slopes. Thanks to reduced noise, higher number of pixel and framerate, we expect a gain (for a given SR) around 1.5–2 magnitudes at all wavelengths in the range 7.5 70% in I-band and 0.6asec seeing) and the sky coverage will be multiplied by a factor 5 at all galactic latitudes. Upgrading the SCAO systems at all the 4 focal stations, SOUL will provide these benefits in 2017 to the LBTI interferometer and in 2018 to the 2 LUCI NIR spectro-imagers. In the same year the SOUL correction will be exploited also by the new generation of LBT instruments: V-SHARK, SHARK-NIR and iLocater.

Optimal control techniques for the adaptive optics system of the LBT

In this paper we will discuss the application of different optimal control techniques for the adaptive optics system of the LBT telescope which comprises a pyramid wavefront sensor and an adaptive secondary mirror. We have studied the application of both the Kalman and the H∞ filter to estimate the temporal evolution of the phase perturbations due to the atmospheric turbulence and the telescope vibrations. We have evaluated the performance of these control techniques with numerical simulations in preparation of the laboratory tests that will be carried out in the Arcetri laboratories.

The Pyramid Phasing Sensor (PYPS)

PYPS is the pyramid wavefront sensor for the phasing and alignment of segmented mirrors developed in the framework of the Active Phase Experiment (APE). In this paper we will present the PYPS opto-mechanical design, and report the experimental results obtained in the Arcetri laboratories prior to its integration in the main APE bench. A piston-correction closed loop was performed under the presence of emulated turbulence (D/r0=33 @ 700nm and V/D=1.9Hz), achieving a final piston error of 10 nm rms in wavefront. Two filtering techniques were developed to average out faster the atmospheric disturbance reducing the required co-phasing time by two orders of magnitude. We will also present the first experimental results obtained with a synthetic interaction matrix attaining a final piston error of the same order of magnitude.

Optical design of the post focal relay of MAORY

The Multi Conjugate Adaptive Optics RelaY (MAORY) is foreseen to be installed at the straight through focus over the Nasmyth platform of the future Extremely Large Telescope (ELT). MAORY has to re-image the telescope focal plane with diffraction limited quality and low geometric distortion, over a field of view of 20 arcsec diameter, for a wavelength range between 0.8 μm and 2.4 μm. Good and uniform Strehl ratio, accomplished with high sky coverage, is required for the wide field science. Two exit ports will be fed by MAORY. The first one is for a wide field Camera that is supposed to be placed on a gravity invariant port with an unvignetted FoV of 53 arcsec x 53 arcsec where diffraction limited optical quality (< 54nm RMS of wavefront error at the wavelength of 1 μm) and very low field distortion (< 0.1% RMS) must be delivered. The requirements regarding the optical quality, distortion and optical interfaces, together with the desire of reducing the number of reflecting surfaces (and consequently the thermal background), optics wavefront error (WFE), overall size, weight and possibly cost, drove the design to have 2 Deformable Mirrors (DMs) with optical power. The Post Focal Relay (PFR) is also required to split the 589 nm wavelength light of the Laser Guide Stars (LGS), used for high order wavefront sensing, by means of a dichroic that lets the light of 6 LGSs, arranged on a circle of about 90 arcsec diameter, pass through and reflects science beam. Behind the dichroic an objective creates the LGS image plane for the WFSs channel. We present in this paper the optical design and the tolerance analysis of the PFR and the objective. The tolerance analysis concerning the manufacturing and the alignment precision is also shown.

MAORY: adaptive optics module for the E-ELT

MAORY is one of the four instruments for the E-ELT approved for construction. It is an adaptive optics module offering two compensation modes: multi-conjugate and single-conjugate adaptive optics. The project has recently entered its phase B. A system-level overview of the current status of the project is given in this paper.

The pyramid wavefront sensor for the high order testbench (HOT)

The High Order Testbench (HOT) is a joint experiment of ESO, Durham University and Arcetri Observatory to built and test in laboratory the performance of Shack-Hartmann and pyramid sensor in a high-order correction loop using a 32x32 actuators MEMS DM. This paper will describe the pyramid wavefront sensor unit developed in Arcetri and now installed in the HOT bench at ESO premises. In the first part of this paper we will describe the pyramid wavefront sensor opto-mechanics and its real-time computer realized with a commercial Linux-PC. In the second part we will show the sensor integration and alignment in the HOT bench and the experimental results obtained at ESO labs. Particular attention will be paid to the implementation of the modal control strategy, like modal basis definition, orthogonalization on the real pupil, and control of edge actuators. A stable closed loop controlling up to 667 modes has been achieved obtaining a Strehl ratio of 90 -- 93% in H band.

The numerical simulation tool for the MAORY multiconjugate adaptive optics system

The Multiconjugate Adaptive Optics RelaY (MAORY) is and Adaptive Optics module to be mounted on the ESO European-Extremely Large Telescope (E-ELT). It is an hybrid Natural and Laser Guide System that will perform the correction of the atmospheric turbulence volume above the telescope feeding the Multi-AO Imaging Camera for Deep Observations Near Infrared spectro-imager (MICADO). We developed an end-to-end Monte- Carlo adaptive optics simulation tool to investigate the performance of a the MAORY and the calibration, acquisition, operation strategies. MAORY will implement Multiconjugate Adaptive Optics combining Laser Guide Stars (LGS) and Natural Guide Stars (NGS) measurements. The simulation tool implement the various aspect of the MAORY in an end to end fashion. The code has been developed using IDL and use libraries in C++ and CUDA for efficiency improvements. Here we recall the code architecture, we describe the modeled instrument components and the control strategies implemented in the code.

LBT observations of the HR 8799 planetary system

We have performed H and KS band observations of the planetary system around HR 8799 using the new AO system at the Large Binocular Telescope and the PISCES Camera. The excellent instrument performance (Strehl ratios up to 80% in H band) enabled the detection of the innermost planet, HR 8799e ,a tH band for the first time. The H and KS magnitudes of HR 8799e are similar to those of planets c and d, with planet e being slightly brighter. Therefore, HR 8799e is likely slightly more massive than c and d .W e also explored possible orbital configurations and their orbital stability. We confirm that the orbits of planets b, c and e are consistent with being circular and coplanar; planet d should have either an orbital eccentricity of about 0.1 or be non-coplanar with respect to b and c. Planet e can not be in circular and coplanar orbit in a 4:2:1 mean motion resonances with c and d, while coplanar and circular orbits are allowed for a 5:2 resonance. The analysis of dynamical stability shows that the system is highly unstable or chaotic when planetary masses of about 5 MJ for b and 7 MJ for the other planets are adopted. Significant regions of dynamical stability for timescales of tens of Myr are found when adopting planetary masses of about 3.5, 5, 5, and 5 MJ for HR 8799b, c, d ,a nde respectively. These masses are below the current estimates based on the stellar age (30 Myr) and theoretical models of substellar objects.