RISTRETTO is the evolution of the original idea of coupling the VLT instruments SPHERE and ESPRESSO,1 aiming at High Dispersion Coronagraphy. RISTRETTO is a visitor instrument that should enable the characterization of the atmospheres of nearby exoplanets in reflected light, by using the technique of high-contrast, high-resolution spectroscopy. Its goal is to observe Prox Cen b and other planets placed at about 35mas from their star, i.e. 2λ/D at λ=750nm. The instrument is composed of an extreme adaptive optics, a coronagraphic Integral Field Unit, and a diffraction-limited spectrograph (R=140.000, λ =620-840 nm).
We present the status of our studies regarding the coronagraphic IFU and the XAO system. The first in particular is based on a modified version of the PIAA apodizer, allowing nulling on the first diffraction ring. Our proposed design has the potential to reach ≥ 50% coupling and ≤ 10−4 contrast at 2λ/D in median seeing conditions.
The SPEED test-bed (Segmented Pupil Experiment for Exoplanet Detection) is a high contrast imaging platform whose prime objective is to study coronagraphy and wavefront shaping for large segmented on-axis telescopes. Active control and temporal stability of residual wavefront errors is one pillar to consider for improving detection yields and getting access to object classes with masses ideally down to exoEarths. The SPEED test-bed being more complex than a simple laboratory test bench but less demanding than an on-sky instrument at a telescope, imposes a specific and adapted system and software control development. The paper reports the design of the SPEED system control hardware and software infrastructure that enables the bench to operate efficiently and safely. Because having experts in software engineering processes for laboratory development is rather difficult to afford, the paper will touch on several design items, highlighting aspects which, in our opinion, may be of particular interest for designers and implementers of laboratory control software.
The SPEED test-bed is completed and operational at Lagrange Laboratory in Nice. The bench optical design allows a wide range of applications in high-contrast imaging: cophasing optics, coronagraphy, and wavefront shaping for large segmented on-axis telescopes. SPEED offers an ad hoc and representative lab environment for studying the effect of pupil fragmentation in a high-correction contrast regime to assess quasi-static speckle control and stability. The SPEED prime goal is to demonstrate high contrast at short angular separations with an unfriendly telescope aperture. After years of developments, from early design to first lights, we thoroughly present the SPEED facility by discussing the principal elements that have driven the design. The main characteristics and exploitation modes of this unique facility are presented.
The segmented pupil experiment for exoplanet detection (SPEED) facility aims to improve knowledge and insight into various areas required for gearing up high-contrast imaging instruments adapted to the unprecedented high angular resolution and complexity of the forthcoming extremely large telescopes (ELTs). SPEED combines an ELT simulator, cophasing optics, wavefront control and shaping with a multi-deformable mirror (DM) system, and optimized small inner-working angle (IWA) coronagraphy. The fundamental objective of the SPEED setup is to demonstrate deep contrast into a dark hole optimized for small field of view and very small IWA, adapted to the hunt of exoplanets in the habitable zone around late-type stars. SPEED is designed to implement an optimized small IWA coronagraph: the phase-induced amplitude apodization complex mask coronagraph (PIAACMC). The PIAACMC consists in a multi-zone phase-shifting focal plane mask (FPM) and two apodization mirrors (PIAA-M1 and PIAA-M2), with strong manufacturing specifications. Recently, a first-generation prototype of a PIAACMC optimized for the SPEED facility has been designed and manufactured. The manufacturing components exhibit high optical quality that meets specifications. In this paper, we present how these components have been characterized by a metrological instrument, an interferential microscope, and then we show what is yielded from this characterization for the FPM and the mirrors. Eventually, we discuss the results and the perspectives of the implementation of the PIAACMC components on the SPEED setup.
The SPEED project aims at developing and testing key recipes for high-contrast imaging at small angular separations with unfriendly telescope apertures. SPEED combines optimized segmented aperture coronagraphy, dual-deformable mirrors wavefront control and shaping architecture for creating a dark hole in the scientific image by deformable mirror (DM) actuation. The challenge is to overcome the various fundamental limitations for quasi-static speckle calibration at very small angular separations. We report on the progress made in elaborating an accurate simulated model of our instrument in preparation for the wavefront control and wavefront shaping strategy with a multi-DM setup.
SPEED – the segmented pupil experiment for exoplanet detection – currently in final integration phase, is designed to test strategies and technologies for high-contrast instrumentation with segmented telescopes by offering an ideal cocoon to progress in these domains with complex telescope apertures. SPEED combines precision segment phasing architectures, optimised small inner-working angle (IWA) coronagraphy, and wavefront shaping to create a small IWA and small field of view (FoV) dark hole in the science detector. Over the years SPEED has made significant hardware and software progress to start the exploitation of the bench. We have completed several key hardware including the common-path wavefront sensor for cophasing optics based on the self-coherent camera (SCC) concept. In this paper, we report on the wavefront sensing strategy designed for SPEED, from the adaptation of the SCC concept to cophasing optics towards an alternative implementation of the conventional SCC, called the fast-modulated SCC, for both wavefront control and shaping applications. We present a progress overview on this wavefront sensor for (i) cophasing control and monitoring from the scientific image, as well as (ii) its interest for the wavefront shaping unit of the bench.
SPEED (Segmented Pupil Experiment for Exoplanet Detection) is an instrumental testbed designed to offer an ideal cocoon to provide relevant solutions in both cophasing and high-contrast imaging with segmented telescopes. The next generation of observatories will be made of a primary mirror with excessive complexity (mirror segmentation, central obscuration, and spider vanes) undoubtedly known to be unfavorable for the direct detection of exoplanets. Exoplanets detection around late-type stars (M-dwarfs) constitutes an outstanding reservoir of candidates, and SPEED integrates all the recipes to pave the road for this science case (cophasing sensors, multi-DM wavefront control and shaping architecture as well as advanced coronagraphy). In this paper, we provide a progress overview of the project and report on the first light with segments cophasing control and monitoring from a coronagraphic image.
Future extremely large telescopes, equipped with high-contrast instruments targeting very small Inner Working Angle, will provide the requisite resolution for detecting exoplanets in the habitable zone around M-stars. However, the ELT segmented pupil shape is unfavourable to high-contrast imaging. In this context, the SPEED project aims to develop and test solutions for high contrast with unfriendly apertures. SPEED will combine a PIAACMC coronagraph and two deformable mirrors for the wavefront shaping. In this paper, we describe an end-to-end model of SPEED, including the Fresnel wavefront propagation, the PIAACMC implementation and the dark hole algorithm, and present a statistical analysis of the predicted performance.
The Phase-Induced Amplitude Apodization Complex Mask Coronagraph (PIAACMC) is a promising corona- graphic device for direct detection of exoplanets with complex segmented telescope apertures. This concept features the bright idea of generating a pupil apodization by reflection on two mirrors whose wavefront maps are specifically optimized, and a complex focal plane mask. In this paper, we report on the design, specifications, and manufacturing of such a coronagraph for the SPEED facility (Segmented Pupil Experiment for Exoplanet Detection) struggled for deep contrast at small angular separation with complex telescope aperture.
Future extremely large telescopes will open a niche for exoplanet direct imaging at the expense of using a primary segmented mirror which is known to hamper high-contrast imaging capabilities. The focal plane diffraction pattern is dominated by bright structures and the way to reduce them is not straightforward since one has to deal with strong amplitude discontinuities in this kind of unfriendly pupil (segment gaps and secondary support). The SPEED experiment developed at Lagrange laboratory is designed to address this specific topic along with high-contrast at very small separation. The baseline design of SPEED will combine a coronagraph and two deformable mirrors to create dark zones at the focal plane. A first step in this project was to identify under which circumstances the deep contrast at small separation is achievable. In particular, the DMs location is among the critical aspect to consider and is the topic covered by this paper.
Extremely Large Telescopes (ELTs) are the next technological step when considering astrophysical observation. They will provide unprecedented angular resolution, thus improving the imaging capability and hopefully allow the imaging of the first Earth-like exoplanet. For technological and mechanical reasons, the primary mirror of these instruments will have to be segmented. To reach the image quality needed for the most demanding observational programs, the segments must be kept aligned below tens of nm RMS. The development of cophasing technics is of prime importance for the next generation of space- and ground-based segmented telescopes. We propose to describe in this paper a new focal plane cophasing sensor that exploits the scientific image of a coronagraphic instrument to retrieve simultaneously piston and tip-tilt misalignments. It is based on the self- coherent camera (SCC) principle and provides a non-invasive system and an efficient phasing sensor from the image domain. Numerical simulations have successfully demonstrated the proper functioning of this system and its algorithms. Along this, work to implement and test the self-coherent camera - phasing sensor (SCC-PS) is currently ongoing and a first look at the cophasing stage of the Segmented Pupil Experiment for Exoplanet Detection (SPEED) will be proposed.
The SPEED project - the Segmented Pupil Experiment for Exoplanet Detection - in development at the Lagrange laboratory, aims at gearing up strategies and technologies for high-contrast instrumentation with segmented telescopes. This new instrumental platform offers an ideal environment in which to make progress in the domain of ELTs and/or space-based missions with complex apertures. It combines all the required recipes (phasing optics, wavefront control/shaping, and advanced coronagraphy) to get to very close angular separation imaging. In this paper, we report on the optical design and subsystems advances and we provide a progress overview.
Searching for nearby exoplanets with direct imaging is one of the major scientific drivers for both space and groundbased programs. While the second generation of dedicated high-contrast instruments on 8-m class telescopes is about to greatly expand the sample of directly imaged planets, exploring the planetary parameter space to hitherto-unseen regions ideally down to Terrestrial planets is a major technological challenge for the forthcoming decades. This requires increasing spatial resolution and significantly improving high contrast imaging capabilities at close angular separations. Segmented telescopes offer a practical path toward dramatically enlarging telescope diameter from the ground (ELTs), or achieving optimal diameter in space. However, translating current technological advances in the domain of highcontrast imaging for monolithic apertures to the case of segmented apertures is far from trivial. SPEED – the segmented pupil experiment for exoplanet detection – is a new instrumental facility in development at the Lagrange laboratory for enabling strategies and technologies for high-contrast instrumentation with segmented telescopes. SPEED combines wavefront control including precision segment phasing architectures, wavefront shaping using two sequential high order deformable mirrors for both phase and amplitude control, and advanced coronagraphy struggled to very close angular separations (PIAACMC). SPEED represents significant investments and technology developments towards the ELT area and future spatial missions, and will offer an ideal cocoon to pave the road of technological progress in both phasing and high-contrast domains with complex/irregular apertures. In this paper, we describe the overall design and philosophy of the SPEED bench.
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