Stack Array Mirrors (SAM) technology offers high order correction, with up to several thousands of actuators, controllable at high frequency, up to several kHz. A new generation of piezo-electric actuators with high reliability has been developed during the last years. This technology is well-adapted for large deformable mirrors (DMs) with thousands of actuators for future needs for Extremely Large Telescopes. We present the design and the modelling of the two large DMs for NFIRAOS, the multi-conjugate adaptive optics system of the Thirty Meter Telescope (TMT): DM0 which shows 3125 actuators and DM11 which shows 4548 actuators. A DM prototype with 616 actuators has been manufactured to validate the manufacturing steps and the specifications of the future large DMs, including their behavior at both ambient and low temperature (-30°C). The prototype includes the new generation of piezo actuators with improved reliability thanks to an optimization of the fabrication processes. Experimental results of accelerated ageing tests and mechanical fatigue are presented. After complete assembly, the prototype is qualified in a specific cool chamber with interferometric measurements. The results are the following: operational stroke higher than 10 μm PV at both ambient and -30°C with uniformity better than 5%, overall non-linearity lower than 5%, resonance frequency of the actuators higher than 10 kHz. Based on the measurements done on the overall temperature range (+20°C to -30°C), the best flat is lower than the goal specification of 10 nm RMS mechanical. An enhanced protected silver coating done by magnetron sputtering allows a high level of reflectivity especially in the near infrared range and long-life durability.
We present recent developments on deformable mirrors (DM) for astronomy with ground-based telescopes. A new generation of actuators with high reliability and high performances has been developed for Stack Array Mirrors. These actuators are suitable for a large range of DMs, including future needs for Extremely Large Telescopes. Design and modelling of large DMs for Thirty Meter Telescope and European Extremely Large Telescope are presented. The Monomorph mirrors combines simplicity and efficiency to correct the wavefront deformation. Astronomical telescopes can benefit of the developments performed on this Monomorph technology for high power laser chains and for spaceborn instrumentation.
The TMT first light Adaptive Optics (AO) facility consists of the Narrow Field Infra-Red AO System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). NFIRAOS is a 60 × 60 laser guide star (LGS) multi-conjugate AO (MCAO) system, which provides uniform, diffraction-limited performance in the J, H, and K bands over 17-30 arc sec diameter fields with 50 per cent sky coverage at the galactic pole, as required to support the TMT science cases. NFIRAOS includes two deformable mirrors, six laser guide star wavefront sensors, and three low-order, infrared, natural guide star wavefront sensors within each client instrument. The first light LGSF system includes six sodium lasers required to generate the NFIRAOS laser guide stars. In this paper, we will provide an update on the progress in designing, modeling and validating the TMT first light AO systems and their components over the last two years. This will include pre-final design and prototyping activities for NFIRAOS, preliminary design and prototyping activities for the LGSF, design and prototyping for the deformable mirrors, fabrication and tests for the visible detectors, benchmarking and comparison of different algorithms and processing architecture for the Real Time Controller (RTC) and development and tests of prototype candidate lasers. Comprehensive and detailed AO modeling is continuing to support the design and development of the first light AO facility. Main modeling topics studied during the last two years include further studies in the area of wavefront error budget, sky coverage, high precision astrometry for the galactic center and other observations, high contrast imaging with NFIRAOS and its first light instruments, Point Spread Function (PSF) reconstruction for LGS MCAO, LGS photon return and sophisticated low order mode temporal filtering.
We present recent experimental results obtained with CILAS deformable mirrors (DMs) or demonstration prototypes in solar and night-time astronomy (with ground-based telescopes) as well as observation of the Earth (with space telescopes). These important results have been reached thanks to CILAS technology range composed of monomorph and piezostack deformable mirrors, drivers and optical coatings. For instance, the monomorph technology, due to a simple architecture can offer a very good reliability for space applications. It can be used for closed or open loop correction of the primary mirror deformation (thermal and polishing aberrations, absence of gravity). It can also allow a real-time correction of wavefront aberrations introduced by the atmosphere up to relatively high spatial and temporal frequencies for ground-based telescopes. The piezostack technology is useful for very high order correction at high frequency and under relatively low operational temperature (down to -30°C), which is required for future Extremely Large Telescopes (ELTs). This wide range of applications is exposed through recent examples of DMs performances in operation and results obtained with breadboards, allowing promising DMs for future needs.
Direct detection and spectral characterization of extra-solar planets is one of the most exciting and challenging areas in
modern astronomy due to the very large contrast between the host star and the planet at very small angular separations.
SPHERE (Spectro-Polarimetric High-contrast Exoplanet Research in Europe) is a second-generation instrument for the
ESO VLT dedicated to this scientific objective. It combines an extreme adaptive optics system, various coronagraphic
devices and a suite of focal instruments providing imaging, integral field spectroscopy and polarimetry capabilities in the
visible and near-infrared spectral ranges.
The extreme Adaptive Optics (AO) system, SAXO, is the heart of the SPHERE system, providing to the scientific
instruments a flat wavefront corrected from all the atmospheric turbulence and internal defects. We present an updated
analysis of SAXO assembly, integration and performance. This integration has been defined in a two step process. While
first step is now over and second one is ongoing, we propose a global overview of integration results. The main
requirements and system characteristics are briefly recalled, then each sub system is presented and characterized. Finally
the full AO loop first performance is assessed. First results demonstrate that SAXO shall meet its challenging
In order to prepare for the construction phase of the two Deformable Mirrors (DMs), which will be used in the Thirty
Meter Telescope (TMT) first light Adaptive Optics (AO) system, Cilas has advanced the design of these two large size
piezo DMs and has manufactured and tested a scaled demonstration prototype. The work done allowed significant
reduction of the risks related to the demanding specifications of the TMT DMs; the main issues were: (i) Large pupil (up
to 370 mm) and high order (up to 74x74); (ii) Relatively low operational temperature (DMs working at -30°C); (iii) New
piezo material. It is important to develop such a prototype to take into account these three specifications all together
(dimension, low temperature and new piezo material). The new prototype is a 6x60 actuators and has the same characteristics as the future TMT DMs. In this paper, we give the conclusions of the work through the presentation of the following items: (i) Design and finite element analysis of the two DMs and prototype; (ii) Test results obtained with the prototype with validation of the finite element analysis and compliance with the TMT AO specifications; (iii) Special focus on thermal behavior, actuator reliability and shape at rest stability.
We provide an update on the development of the first light adaptive optics systems for the Thirty Meter Telescope
(TMT) over the past two years. The first light AO facility for TMT consists of the Narrow Field Infra-Red AO
System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). This order 60 × 60 laser guide star
(LGS) multi-conjugate AO (MCAO) architecture will provide uniform, diffraction-limited performance in the
J, H, and K bands over 17-30 arc sec diameter fields with 50 per cent sky coverage at the galactic pole, as
is required to support TMT science cases. Both NFIRAOS and the LGSF have successfully completed design
reviews during the last twelve months. We also report on recent progress in AO component prototyping, control
algorithm development, and system performance analysis.
In order to mitigate the risks of development of the M4 adaptive mirror for the E-ELT, CILAS has proposed to build a
demonstration prototype and breadboards dedicated to this project. The objectives of the demonstration prototype
concern the manufacturing issues such as mass assembly, integration, control and polishing but also the check the global
dynamical and thermal behaviour of the mirror. The local behaviour of the mirror (polishing quality, influence function,
print through...) is studied through a breadboard that can be considered as a piece of the final mirror. We propose in this
paper to present our breadboard strategy, to define and present our mock-up and to comment the main results and lessons
CILAS proposes a M4 adaptive mirror (M4AM) that corrects the atmospheric turbulence at high frequencies and residual
tip-tilt and defocus due to telescope vibrations by using piezostack actuators. The design presents a matrix of 7217
actuators (triangular geometry, spacing equal to 29 mm) leading to a fitting error reaching the goal. The mirror is held by
a positioning system which ensures all movements of the mirror at low frequency and selects the focus (Nasmyth A or B)
using a hexapod concept. This subsystem is fixed rigidly to the mounting system and permits mirror displacements. The
M4 control system (M4CS) ensures the connection between the telescope control/monitoring system and the M4 unit - positioning system (M4PS) and piezostack actuators of the M4AM in particular. This subsystem is composed of
electronic boards, mechanical support fixed to the mounting structure and the thermal hardware. With piezostack
actuators, most of the thermal load is minimized and dissipated in the electronic boards and not in the adaptive mirror.
The mounting structure (M4MS) is the mechanical interface with the telescope (and the ARU in particular) and ensures
the integrity and stability of M4 unit subsystems. M4 positioning system and mounting structure are subcontracted to
Increasing dimensions of ground based telescopes and adaptive optics needs for these instruments require wide
deformable mirrors with a high number of actuators to compensate the effects of the atmospheric turbulence on the wave
fronts. The new dimensions and characteristics of these deformable mirrors lead to the apparition of structural vibrations,
which may reduce the rejection band width of the adaptive optics control loop.
The aim of this paper is the study of the dynamic behavior of a
1-meter prototype of E-ELT's deformable mirror in order
to identify its eigenmodes and to propose some ways to control its vibrations. We first present the first eigenmodes of the
structure determined by both finite element analysis and experimental modal analysis. Then we present the frequency
response of the prototype to a tilt excitation to estimate the effects of its vibrations on the adaptive optics loop. Finally
we suggest a method to control the dynamics of the deformable mirror.
Adaptive optics (AO) is essential for many elements of the science case for the Thirty Meter Telescope (TMT). The
initial requirements for the observatory's facility AO system include diffraction-limited performance in the near IR, with
50 per cent sky coverage at the galactic pole. Point spread function uniformity and stability over a 30 arc sec field-ofview
are also required for precision photometry and astrometry. These capabilities will be achieved via an order 60×60
multi-conjugate AO system (NFIRAOS) with two deformable mirrors, six laser guide star wavefront sensors, and three
low-order, IR, natural guide star wavefront sensors within each client instrument. The associated laser guide star facility
(LGSF) will employ 150W of laser power at a wavelength of 589 nm to generate the six laser guide stars.
We provide an update on the progress in designing, modeling, and validating these systems and their components over
the last two years. This includes work on the layouts and detailed designs of NFIRAOS and the LGSF; fabrication and
test of a full-scale prototype tip/tilt stage (TTS); Conceptual Designs Studies for the real time controller (RTC) hardware
and algorithms; fabrication and test of the detectors for the
laser- and natural-guide star wavefront sensors; AO system
modeling and performance optimization; lab tests of wavefront sensing algorithms for use with elongated laser guide
stars; and high resolution LIDAR measurements of the mesospheric sodium layer. Further details may be found in
specific papers on each of these topics.
The Narrow Field Infrared Adaptive Optics System (NFIRAOS) is the first light Laser Guide Star (LGS)
Multi-Conjugate Adaptive Optics (MCAO) system for TMT. NFIRAOS needs to correct 2-axis tip/tilt jitter
disturbances, including both telescope vibration and atmospheric tip/tilt, to a residual of 2 milli-arcsecond (mas)
RMS with 50% sky coverage at the Galactic pole. NFIRAOS will utilize multiple infrared tip/tilt sensors, as
sky coverage benefits greatly from wavefront sensing in the near IR where guide star densities are greater and
the NFIRAOS AO system "sharpens" the guide star images. NFIRAOS will also utilize type II woofer-tweeter
control to correct tip/tilt jitter. High amplitude, low bandwidth errors are corrected by a tip/tilt platform
(woofer), whereas the low amplitude, high bandwidth disturbances are corrected by the deformable mirrors. A
prototype development effort for the relatively large, massive DM tip/tilt stage is now underway. Detailed Monte
Carlo simulations of the complete architecture indicate that the sky coverage and tip/tilt control requirement
for NFIRAOS can be met, with some margin available for stronger input disturbances or shortfalls in component
A 42 meters telescope does require adaptive optics to provide few milli arcseconds resolution images. In the current
design of the E-ELT, M4 provides adaptive correction while M5 is the field stabilization mirror. Both mirrors have an
essential role in the E-ELT telescope strategy since they do not only correct for atmospheric turbulence but have also to
cancel part of telescope wind shaking and static aberrations. Both mirrors specifications have been defined to avoid
requesting over constrained requirements in term of stroke, speed and guide stars magnitude. Technical specifications
and technological issues are discussed in this article. Critical aspects and roadmap to assess the feasibility of such
mirrors are outlined.
Increasing dimensions of ground based telescopes while implementing Adaptive Optics systems to cancel both structural
deformations and atmospheric effects require very large diameters deformable mirrors (DM) and a high number of
actuators with large strokes. This has led for the future E-ELT to a 2.5 m diameter DM getting about 8000 actuators.
This paper presents a local and a global model of the DM in order to both study its influence function and its dynamical
behavior. In the first part, influence function of the mirror is calculated. Results obtained by an analytical way are
compared to those obtained numerically. In the second part, modal analysis of the mirror is presented. Results are limited
to the first modes. Modal analysis is also only made for the base plate to derive the specific influence of DM's
components on the global dynamic behavior. In the last part, optimization methods are used to help designing a 1 m
prototype of the DM.
We present the CILAS "Piezo Array" technology for Deformable Mirrors (DMs). Its main technical advantages are high
order, large stroke, large bandwidth, high optical quality and very low dependence to temperature and environment. This
technology can lead, on one hand, to very high order (several thousands), small inter-actuator spacing (1 mm range)
DMs and, on the other hand, to large aperture DMs (2.5 m range). Both are needed for next generation of instrumentation
and Extremely Large Telescopes (ELTs). A second family of DMs used for astronomy is the "Bimorph" technology.
This piezo technology also allowed to obtain very good results on the most famous telescopes in the world.
Atmospheric turbulence compensation via adaptive optics (AO) will be essential for achieving most objectives of the
TMT science case. The performance requirements for the initial implementation of the observatory's facility AO system
include diffraction-limited performance in the near IR with 50 per cent sky coverage at the galactic pole. This capability
will be achieved via an order 60x60 multi-conjugate AO system (NFIRAOS) with two deformable mirrors optically
conjugate to ranges of 0 and 12 km, six high-order wavefront sensors observing laser guide stars in the mesospheric
sodium layer, and up to three low-order, IR, natural guide star wavefront sensors located within each client instrument.
The associated laser guide star facility (LGSF) will consist of 3 50W class, solid state, sum frequency lasers,
conventional beam transport optics, and a launch telescope located behind the TMT secondary mirror.
In this paper, we report on the progress made in designing, modeling, and validating these systems and their components
over the last two years. This includes work on the overall layout and detailed opto-mechanical designs of NFIRAOS and
the LGSF; reliable wavefront sensing methods for use with elongated and time-varying sodium laser guide stars;
developing and validating a robust tip/tilt control architecture and its components; computationally efficient algorithms
for very high order wavefront control; detailed AO system modeling and performance optimization incorporating all of
these effects; and a range of supporting lab/field tests and component prototyping activities at TMT partners. Further
details may be found in the additional papers on each of the above topics.
We present a novel architecture of deformable mirror dedicated to lasers. The new monomorph mirror presents the advantage of avoiding high spatial frequency on the residual wavefront enabling propagation of the laser beam without any energy modulation. The obtained residual wavefront is 3.4 nm rms wavefront.
In this paper, we provide an overview of the adaptive optics (AO) program for the Thirty Meter Telescope (TMT) project, including an update on requirements; the philosophical approach to developing an overall AO system architecture; the recently completed conceptual designs for facility and instrument AO systems; anticipated first light capabilities and upgrade options; and the hardware, software, and controls interfaces with the remainder of the observatory. Supporting work in AO component development, lab and field tests, and simulation and analysis is also discussed. Further detail on all of these subjects may be found in additional papers in this conference.