Small-ELF is a 3.5-meter telescope currently in development that will serve as a technology demonstrator for the much larger telescope named ELF (Exo-Life Finder). The ELF is proposed to be built with a minimum effective diameter of 12- meters and is designed to be scalable to a much larger size. The primary objective of the proposed design approach is to radically improve the system’s capabilities for direct imaging of exoplanets while keeping costs well below the current flagship observatories. The basic optical design of Small-ELF consists of an annulus of 15 primary mirror sub-apertures, mounted on an alt-az configuration. As a technology demonstrator, the mechanical design of Small-ELF intends to deliver a versatile and reliable experimental platform to implement and verify several new techniques: the use of a tensegrity-based configuration for a light-weight supporting structure, the use of tensioned ropes to actively adjust the telescope geometry, methods of accommodating sub-apertures of significant weight variations, and methods of controlling and mitigating vibrations associated with light-weighted structures through active and passive damping systems. The design also adopts techniques for efficient precision manufacturing and cost control. The unique optical layout and application of tensegrity produce significant weight and subsequent cost reductions. This technology demonstrator tackles the cost and scalability problem faced by most existing telescopes and intends to open a new chapter in large telescope structural design methodology.

Ground-breaking science like the search for life in the atmospheres of exoplanets requires telescopes with extemely large diameters (>35m). Emergingtechnology can build competing and complementary to the large astronomical telescopes being built and designed to achieve some specific science cases such as the detection and study of life-bearing exoplanets in the nearest 100 star systems. In particular, Fizeau optics, non-subtractive shaping of thin mirrors, photonics and neural-network wavefront sensing, active/adaptive optics, integral robotics and tensegrity structures, are key.Our team is currently working on the design and construction of a 3.5m precursor telescope, using some of these disruptive technologies. The so-called Small ExoLife Finder (Small-ELF) costs about 5Me and can be finished within the next 5 years to detect nearby large exoplanets. This research and development was recently fundedby the European Union to create a new sustainable "Laboratory for Innovation in Optomechanics" at the IAC (Tenerife) led by Prof Jeff Kuhn. LIOM plans for a 50m ExoLife Finder to be built within 10 years for about 200Meur - more than an order of magnitude less than the Keck-era and ELT telescopes. LIOM aims at (1) developing ultra-thin light mirrors with novel engineered materials to reduce the cost and weight of future telescopes. Moreover, our team is developing (2) designing lighter structures with pre-tensioned cables to support mirrors and lighten structures, and (3) integrating photonic devices that allow more thermal and mechanical stability cost savings with high replicability.The talk will review our progress on all these fronts.

The small ExoLife Finder (sELF) telescope is a 3.4m diameter fixed pupil tracking Fizeau interferometer. Its design relies on several new technologies the ELF-PLANETS consortium has championed that will enable large narrow-field optical coronagraphic direct imaging. These distinguish it from other segmented aperture telescopes by its light weight, low cost, and its capability to create a coronagraphic point spread function with the telescope pupil, ahead of the secondary optics. This diffractive control emphasizes high dynamic range imaging in the presence of a bright central star in a narrow field-of-view. Its optomechanical design uses elements of tensegrity combined with thin (2mm thick by 0.5m diameter) off-axis parabola segments to decrease both the optical payload and mechanical structural mass. The sELF optomechanical design has been completed and contracts for construction in the Canary Islands will be tendered during the 1st quarter of 2023

We have taken advantage of the implementation of an adaptive optics system on the Themis solar telescope to implement innovative strategies based on an inverse problem formulation for the control loop. Such an approach encompassing the whole system implies the estimation of the pixel variances of the Shack-Hartmann wavefront sensor, a novel real-time method to extract the wavefront slopes as well as their associated noise covariance, and the computation of pseudo-open loop data. The optimal commands are computed by iteratively solving a regularized inverse problem with spatio-temporal constraints including Kolmogorov statistics. The latency of the dedicated real-time control software with conventional CPU is shorter than 300 μs from the acquisition of the raw 400 × 400 pixel wavefront sensor image to the sending of the commands.

The small ExoLife Finder (sELF) telescope is a 3.4m diameter fixed pupil tracking Fizeau interferometer. Its design relies on several new technologies the ELF-PLANETS consortium has championed that will enable large narrow-field optical coronagraphic direct imaging. These distinguish it from other segmented aperture telescopes by its light weight, low cost, and its capability to create a coronagraphic point spread function with the telescope pupil, ahead of the secondary optics. This diffractive control emphasizes high dynamic range imaging in the presence of a bright central star in a narrow field-of-view. Its optomechanical design uses elements of tensegrity combined with thin (2mm thick by 0.5m diameter) off-axis parabola segments to decrease both the optical payload and mechanical structural mass. The sELF optomechanical design has been completed and contracts for construction in the Canary Islands will be tendered during the 1st quarter of 2023

Technology now exists to enable large optical systems that are capable of resolving and measuring faint sources not accessible with current remote sensing instruments and detectors. The possibility of creating ground-based telescopes at the 50m-scale with sufficient wavefront control to both fully overcome the effects of the atmosphere, but with exquisite coronagraphic capability starting at the telescope entrance pupil, means we may solve some of the most fundamental cross-cutting scientific questions: like, "is there life outside of the solar system?". The IAC is part of a consortium with the University of Hawaii and Universities in Lyon to develop the technologies needed for the next generation telescopes aimed at direct imaging of exoplanets around bright stars: the "ExoLife Finder (ELF)" telescope. We have a detailed design for a 3.5-m diameter prototype, nicknamed Small-ELF, to be built and installed at Teide Observatory by 2025. I will present the technological and scientific challenges of such telescope.

SPHERE (Beuzit et al,. 2019) has now been in operation at the VLT for more than 5 years, demonstrating a high level of performance. SPHERE has produced outstanding results using a variety of operating modes, primarily in the field of direct imaging of exoplanetary systems, focusing on exoplanets as point sources and circumstellar disks as extended objects. The achievements obtained thus far with SPHERE (~200 refereed publications) in different areas (exoplanets, disks, solar system, stellar physics...) have motivated a large consortium to propose an even more ambitious set of science cases, and its corresponding technical implementation in the form of an upgrade. The SPHERE+ project capitalizes on the expertise and lessons learned from SPHERE to push high contrast imaging performance to its limits on the VLT 8m-telescope. The scientific program of SPHERE+ described in this document will open a new and compelling scientific window for the upcoming decade in strong synergy with ground-based facilities (VLT/I, ELT, ALMA, and SKA) and space missions (Gaia, JWST, PLATO and WFIRST). While SPHERE has sampled the outer parts of planetary systems beyond a few tens of AU, SPHERE+ will dig into the inner regions around stars to reveal and characterize by mean of spectroscopy the giant planet population down to the snow line. Building on SPHERE's scientific heritage and resounding success, SPHERE+ will be a dedicated survey instrument which will strengthen the leadership of ESO and the European community in the very competitive field of direct imaging of exoplanetary systems. With enhanced capabilities, it will enable an even broader diversity of science cases including the study of the solar system, the birth and death of stars and the exploration of the inner regions of active galactic nuclei.

The ExoLife Finder telescope concept combines elements of a fixed pupil telescope with an interferometer in order to achieve very large apertures, high angular resolution and high contrast. The Small ELF (SELF) project is a precursor instrument under construction in the Canary Islands. By combining 15x50cm off-axis parabolic primary segments with 15 off-axis elliptical secondaries in a circular ring SELF achieves the angular resolution of a 3.5m diameter telescope allowing in addition direct “dark hole” coronagraphy by applying specific phase displacements to the subapertures to create nulling in a small area of the field of view. Wavefront sensing and control is done using machine learning observations of simultaneous speckle images in combination with a Mach-Zehnder wavefront sensing for high order wavefront control. Extreme adaptive optics (XAO) systems have severe difficulties to cope with the diluted apertures, and to meet the high contrast requirements: high speed and high accuracy (~ 10 nm) at 5-10 cm spatial scale. An innovative high order adaptive optics system using a self-referenced Mach-Zehnder wavefront sensor has been proposed to counteract these limitations. In this paper, we report on our numerical simulations of the SELF XAO system and on the experimental results obtained for such configuration on our bench dedicated to high contrast. The XAO system delivers high strehl ratio (>95%) while operating in synergy with focal plane wavefront sensing to support cophasing and dark hole coronography in order to reach very high contrast performances.

The constantly increasing needs for astronomical imaging of ever fainter objects as well as for imaging the Earth from space require much higher angular resolution and dynamic range than current optical telescopes can deliver. Mirrors are the key elements of these systems; but they are technologically difficult to improve because they must maintain an exceedingly precise shape while resisting deformations (for example from gravity and/or variable wind loads) in the open environments in which they must operate. Our interdisciplinary novel technology will establish a new paradigm: we will shape thin, very smooth, “fire-polished,” lightweight glass to a predetermined curvature and generate dynamically controlled stiffness by using the addressable energy of electroactive polymers (EAPs) to resist environmental deformations – making what we call a “Live” Mirror.

An adaptive optics system with a single deformable mirror is being implemented on the THEMIS 90cm solar telescope. This system is designed to operate in the visible and is required to be as robust as possible in order to deliver the best possible correction in any atmospheric conditions, even if wavefronts are sensed on some low-contrast solar granulation. In extreme conditions, the images given by the subapertures of the Shack-Hartmann wavefront sensor get randomly blurred in space, in the set of subapertures, and the distribution of blurred images is rapidly changing in time, some of them possibly fading away. The algorithms we have developed for such harsh conditions rely on inverse problem approach. As an example, with the gradients of the wavefronts, the wavefront sensor also estimates their errors, including their covariance. This information allows the control loop to promptly optimize itself to the fast varying conditions, both in space (wavefront reconstruction) and in time. A major constraint is to fit the calculations in a low-cost multi-core CPU. An overview of the algorithms in charge of implementing this strategy is presented, focusing on wavefront sensing.

We describe a new development for a full 3D-printed-force actuator based on an advanced electroactive polymer (EAP) dedicated to large and live optical mirror applications, i.e., Live-Mirror Project (https://www.planets.life/live-mirror). The thin-film casting method was used to additively manufacture actuators, and we developed an integrating 3D printing technology to the EAP force-actuator production. Our 3D-printed actuator consists of the plasticized terpolymer layer (polyvinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene (PVDF-TrFE-CTFE) doped with diisononyl phthalate (DINP) plasticizer) sandwiched between two electrodes layers made of conductive terpolymer carbon black (CB) composite. The conductive CB layers were developed here to have a high electrical conductivity that can be used under significant voltage. We also made compatible blends with an actuator layer based on DINP polymer. Several fully 3D-printed EAP proof-of-concept actuator configurations were printed on a two-millimeters thick flat glass, i.e., an optical mirror surface. Its electromechanical performance was analyzed as a function of actuator volume, layer number, and electrical field intensity.

LiveMetaOptics presented the Exo-life finder (ELF) telescope combined with the hybrid dynamic structure of live and light active mirror named as “Live-mirror”. Recently we reported the idea of active optical surface correction using the advantage of an electromechanical stimulator to deform mirror surface in a significant correction scale. An effort to develop a conventional electroactive polymer (EAP) actuator through Live-mirror application has been taken the new approach, assembling EAP actuator via additive manufacturing or 3D printing technology. The approach of next-generation mirror leaned on 3D printing technological advancement is able to unlock the principles of a potentially new actuator manufacturing technique. Full 3D print of modified EAP was formulated with plasticized terpolymer for an active layer and terpolymer/CB composite for printed electrodes. Though rudimentary of electroactive polymer, the full-printed actuator could transfer its transversal stress or shear force to shape the mirror surface under low applied electric fields. We described here as well creating multilayer structures with capabilities well beyond those of the individual actuator components. Our various configurations of printed actuators could achieve glass surface deformation in a range of 50 nm to 2 µm considering the maximum glass deformation. As a result of material modification coupled with 3D printing technology, we can increase productivity while enabling a mass and cost reduction and an increase of the parts functionality in terms of the real application.

Herein, an advanced concept to enhance the actuation ability of electroactive polymers (EAPs) based on modified terpolymer P(VDF-TrFE-CFE) is proposed. Such a polymer matrix attracts a great deal of attention because of its outstanding electromechanical coupling property, particularly when doped with plasticizers, e.g., diisononyl phthalate (DINP). Herein, it is demonstrated that by optimizing the structure's multilayer design, the electromechanical coupling of the modified terpolymer is enhanced with its high dielectric permittivity, low Young's modulus, and exceptional dielectric strength. This leads to a large strain response as well as a high mechanical energy density at relatively low electric fields according to the electrostriction phenomena. The concept of stacked multilayers is demonstrated as a simple and effective technique to boost the actuation abilities. Experimental results in accordance with numerical models show actuator performance with a large electromechanical response. This technology shows feasibility for active optical surface shape control. The potential of multiple-stack actuators is tested in a small prototype. This demonstrated mirror optical shape control and correction with a few degrees of freedoms. The proposed Live Mirror technology is useful for ground- and space-based astronomy and communications telescopes.

The novelty of correcting optical mirrors surface in a few microns of the desired precisely-shaped are supported by electroactive polymer actuating/sensing devices. The P(VDF-TrFE-CFE) terpolymer with the 10 % DINP plasticizer has field as EAP which showed 10 times higher in longitudinal strain with respect to the neat one and the increase of total axial strain from 0.4 % - 3.0 % with the multilayer sample 1 to 8 layers respectively. The actuator stack was integrated to the mirror in order to prove the concept of adaptive mirror which is able to reach to goal of a few micron mirror deformation.

The interdisciplinary approach presented here creates next-generation large mirrors using electroactive polymer (EAP) actuators without classical glass abrasive polishing ("live mirrors"). The outstanding electromechanical coupling properties of terpolymer are taken advantage of, particularly when doped with plasticizer, e.g., diisononyl phthalate (DINP). This doped terpolymer creates a large strain response as well as excellent mechanical energy density under relatively low electric fields. Classical EAPs (e.g., polyurethane, silicone) require extremely high input voltages to reach sufficient mechanical strain. Using the high-permittivity doped terpolymer and the concept of stacking multilayers, high displacements and large forces are generated. The actuation performance of multilayered terpolymer filled with DINP has been proven to shape mirror glass with a preliminary prototype of an 8-layer actuator stack. The experimental results demonstrate surface deformations under load conditions of several microns. This is large enough to usefully control large optical telescope mirrors. This technology may enable much larger high-quality optical mirror systems for ground- and space-based astronomy and communications telescopes.

Optical communication and remote sensing (on the ground and in space) including astronomy requesting high-dynamic range observations are the next frontiers in high-bandwidth communication and civil space surveillance technologies. Each requires very precise glass mirror technology, which has not kept pace with corresponding optical and infrared sensor advances. Consequently communication and remote sensing systems are currently limited by the cost and manufacturing restrictions of their high-quality optics. We are developing a new and interdisciplinary technology for creating extremely lightweight diffractionlimited meta-material-based optical systems with exceptional optical quality spectacularly lower cost and production time — Live-Mirror. Notably such new technology is crucial to the development of dedicated high angular resolution and high-contrast telescope concept – The ExoLife Finder (ELF) Telescope – to the exoplanets studies and related science such as detecting life and even civilizations on Earth-like planets.

Currently planned massively segmented telescopes like the European Extremely Large Telescope (EELT)1 or the Thirty Meter Telescope (TMT)2, use "Keck-era" optics. Their mirror subapertures create a dynamically rigid primary optical surface from 100's of 1m-scale few-cm thick mirrors. We suggest that a dedicated telescope for distinguishing reflected exoplanet light from its host star may not follow these design principles. To reduce moving mass and telescope-scattered light, a post-Keck era large telescope could use new technologies that replace this opto-mechanical stiffness with massively parallel active electro-optics and interferometric concepts. This opens the intriguing possibility of building a dedicated ground-based exoplanet telescope with an aperture of 20m at a cost-scale of $100M. This is a compelling reason for exploring what we call "synthetic aperture" or "hybrid optical telescopes." Even larger apertures that could be an order of magnitude less costly per square meter than comparable Keck-like optics are possible. Here we consider an optical system built from a relatively "floppy" optical structure and scalable interferometrically phased, moderate size (5m diameter), subapertures. This ExoLife Finder (ELF) telescope is sensitive to optical biomarker signals and has the power to map the surfaces of nearby M-dwarf exoplanets on subcontinental scales.

The exponential growth in exoplanets studies and related science such as detecting life and even civilizations on Earth-like planets requires high angular resolution and high-contrast observations. Such appealing sciences cases are a powerful reason for developing a dedicated high contrast telescope concept – The ExoLife Finder (ELF) Telescope. Here we describe the ELF overall optical concept, its preliminary Adaptive Optics concept and a novel and revolutionary technology to produce mirrors making use of force-sensor-actuator elements that are 3D-printed onto very thin slumped glass-sandwich elements of fire-polished glass – a very precise aspherical optical surface dedicated to high contrast measurements.

THEMIS is a 90 cm solar telescope which undergoes a rejuvenation of its scientific instruments. In particular, it is about to be equipped with an adaptive optics (AO) system with a bandwidth of at least 1 kHz and featuring a 97 actuator deformable mirror and 10x10 Shack-Hartmann wavefront sensor. Nowadays, the computational power required by such a system can be provided by current multi-core CPU. We have therefore implemented from scratch the real-time control system in pure software using Julia,(1) a new language for technical computations, and running on Linux OS. Our main motivation was to be able to exploit new advances in wavefront sensing and adaptive optics control. With a computational cost comparable to state-of-the-art but sub-optimal methods used in solar AO, our wavefront sensing algorithm estimates the local slopes and their covariances following a maximum likelihood registration method. THEMIS AO system has a modest size but can be used to assert the benefits of maximum a posteriori (MAP) wavefront sensing and control,(2, 3) of accounting of the covariances of the measure and of the temporal correlation of the turbulent wavefront.