All high-contrast imaging instruments are plagued by non-common path aberrations (NCPA). MagAO-X has a unique second-stage Adaptive Optics (AO) system that contains a dedicated deformable mirror (DM) that is not seen by the main AO wavefront sensor for NCPA compensation. Our second stage AO system decouples the focal plane wavefront control from the main AO loop that is driven by a pyramid wavefront sensor. This Non-Common Path Aberration Correction DM (ncpcDM) has been recently upgraded from an ALPAO-97 to a Boston Micromachine Kilo-DM. The large increase in the number of actuators on the ncpcDM enables high-order focal plane wavefront control algorithms such as implicit Electric Field Conjugation (iEFC). We developed iEFC on MagAO-X to create a data-driven approach to coronagraphic dark hole digging. Our preliminary results indicate that iEFC together with the second-stage AO system can improve the raw contrast of MagAO-X by one to two orders of magnitude with an even larger gain expected after post-processing. We will review the focal-plane wavefront sensing and control strategies of MagAO-X and present the first on-sky results of iEFC with the second-stage AO system.
The next generation of extreme adaptive optics (AO) must be calibrated exceptionally well to achieve the desired contrast for ground-based direct imaging exoplanet targets. Current wavefront sensing and control system responses deviate from lab calibration throughout the night due to non linearities in the wavefront sensor (WFS) and signal loss. One cause of these changes is the optical gain (OG) effect, which shows that the difference between actual and reconstructed wavefronts is sensitive to residual wavefront errors from partially corrected turbulence. This work details on-sky measurement of optical gain on MagAO-X, an extreme AO system on the Magellan Clay 6.5m. We ultimately plan on using a method of high-temporal frequency probes on our deformable mirror to track optical gain on the Pyramid WFS. The high-temporal frequency probes, used to create PSF copies at 10-22 λ/D, are already routinely used by our system for coronagraph centering and post-observation calibration. This method is supported by the OG measurements from the modal response, measured simultaneously by sequenced pokes of each mode. When tracked with DIMM measurements, optical gain calibrations show a clear dependence on Strehl Ratio, and this relationship is discussed. This more accurate method of calibration is a crucial next step in enabling higher fidelity correction and post processing techniques for direct imaging ground based systems.
Refractive index changes in the Earth’s atmosphere cause differential atmospheric dispersion, an unwanted wavelength dependency in the observations of ground-based astronomical telescopes. These dispersion effects cause smearing of the telescope’s point-spread function (PSF), resulting in difficulty when performing high-contrast imaging at small inner-working angles due to reduced coronagraph light-blocking efficiency. An Atmospheric Dispersion Corrector (ADC) is used to compensate for these effects. Current approaches use analytical models to anticipate dispersion effects at different telescope zenith angles; however, uncertainties in these models lead to over- or under-correction of the true atmospheric dispersion by the ADC. As an alternative, we present a closed-loop approach to this problem using the Magellan Adaptive Optics eXtreme (MagAO-X) instrument to measure and correct for dispersion effects as they appear. Residual atmospheric dispersion can be measured from artificial speckles on our science image, which are created by sinusoidal phase patterns on the deformable mirror. We use a forward model phase retrieval approach to determine the proper correction parameters to send to the ADC. Increasing the precision of our dispersion compensation is especially important as we prepare for the next generation of ground-based observations with the Giant Magellan Telescope.
High-contrast imaging data analysis depends on removing residual starlight from the host star to reveal planets and disks. Most observers do this with principal components analysis (i.e. KLIP) using modes computed from the science images themselves. These modes may not be orthogonal to planet and disk signals, leading to over-subtraction. The wavefront sensor data recorded during the observation provide an independent signal with which to predict the instrument point-spread function (PSF). MagAO-X is an extreme adaptive optics (ExAO) system for the 6.5-meter Magellan Clay telescope and a technology pathfinder for ExAO with GMagAO-X on the upcoming Giant Magellan Telescope. MagAO-X is designed to save all sensor information, including kHz-speed wavefront measurements. Our software and compressed data formats were designed to record the millions of training samples required for machine learning with high throughput. The large volume of image and sensor data lets us learn a PSF model incorporating all the information available. This allows us to probe smaller star-planet separations at greater sensitivities, which will be needed for rocky planet imaging.
The high contrast and spatial resolution requirements for directly imaging exoplanets requires effective coordination of wavefront control, coronagraphy, observation techniques, and post-processing algorithms. However, even with this suite of tools, identifying and retrieving exoplanet signals embedded in resolved scattered light regions can be extremely challenging due to the increased noise from scattered light off the circumstellar disk and the potential misinterpretation of the true nature of the detected signal. This issue pertains not only to imaging terrestrial planets in habitable zones within zodiacal and exozodiacal emission but also to young planets embedded in circumstellar, transitional, and debris disks. This is particularly true for Hα detection of exoplanets in transitional disks. This work delves into recent Hα observations of three transitional disks systems with MagAO-X, an extreme adaptive optics system for the 6.5-meter Magellan Clay telescope. We employed angular differential imaging (ADI) and simultaneous spectral differential imaging (SSDI) in combination with KLIP, a PCA algorithm in post-processing, for optimal starlight suppression and quasi-static noise removal. We discuss the challenges in protoplanet identification with MagAO-X in environments rich with scattered and reflected light from disk structures and explore a potential solution for removing noise contributions from real astronomical objects with current observation and post-processing techniques.
MagAO-X is the coronagraphic extreme adaptive optics system for the 6.5m Magellan Clay Telescope. We report the results of commissioning the first phase of MagAO-X. Components now available for routine observations include: the >2kHz high-order control loop consisting of a 97 actuator woofer deformable mirror (DM), a 2040 actuator tweeter DM, and a modulated pyramid wavefront sensor (WFS); classical Lyot coronagraphs with integrated low-order (LO) WFS and control using a third 97-actuator non-common path correcting (NCPC) DM; broad band imaging in g, r, i, and z filters with two EMCCDs; simultaneous differential imaging in Hα; and integral field spectroscopy with the VIS-X module. Early science results include the discovery of an Hα jet, images of accreting protoplanets at Hα, images of young extrasolar giant planets in the optical, discovery of new white dwarf companions, resolved images of evolved stars, and high-contrast images of circumstellar disks in scattered light in g-band (500nm). We have commenced an upgrade program, called “Phase II”, to enable high-contrast observations at the smallest inner working angles possible. These upgrades include a new 952 actuator NCPC DM to enable coronagraphic wavefront control; phase induced amplitude apodization coronagraphs; new fast cameras for LOWFS and Lyot-LOWFS; and real-time computer upgrades. We will report the status of these upgrades and results of first on-sky testing in March-May 2024.
We present the preliminary design of GMagAO-X, the first-light high-contrast imager planned for the Giant Magellan Telescope. GMagAO-X will realize the revolutionary increase in spatial resolution and sensitivity provided by the 25 m GMT. It will enable, for the first time, the spectroscopic characterization of nearby potentially habitable terrestrial exoplanets orbiting late-type stars. Additional science cases include: reflected light characterization of mature giant planets; measurement of young extrasolar giant planet variability; characterization of circumstellar disks at unprecedented spatial resolution; characterization of benchmark stellar atmospheres at high spectral resolution; and mapping of resolved objects such as giant stars and asteroids. These, and many more, science cases will be enabled by a 21,000 actuator extreme adaptive optics system, a coronagraphic wavefront control system, and a suite of imagers and spectrographs. We will review the science-driven performance requirements for GMagAO-X, which include achieving a Strehl ratio of 70% at 800 nm on 8th mag and brighter stars, and post-processed characterization at astrophysical flux-ratios of 1e-7 at 4 lambda/D (26 mas at 800 nm) separation. We will provide an overview of the resulting mechanical, optical, and software designs optimized to deliver this performance. We will also discuss the interfaces to the GMT itself, and the concept of operations. We will present an overview of our end-to-end performance modeling and simulations, including the control of segment phasing, as well as an overview of prototype lab demonstrations. Finally, we will review the results of Preliminary Design Review held in February, 2024.
The upcoming Extremely Large Telescopes have the angular resolution and light collecting area that is necessary to observe biosignatures in the atmospheres of Earth-like planets. High-contrast imaging instruments will play a large role in this because observing planets directly overcomes many of the observational limitations of other exoplanet detection techniques. The influence of the bright star can be significantly reduced by spatially resolving the dim planet, allowing characterization of the planet and its atmosphere. However, the required wavefront sensing, and control (WFS&C) technologies have yet to be proven on-sky. The Magellan Adaptive Optics eXtreme (MagAO-X) instrument is a new visible to near-infrared high-contrast imaging system that operates as a testbed for the development and testing of WFS&C techniques.
We present a status update for MagAO-X, a 2000 actuator, 3.6 kHz adaptive optics and coronagraph system for the Magellan Clay 6.5 m telescope. MagAO-X is optimized for high contrast imaging at visible wavelengths. Our primary science goals are detection and characterization of Solar System-like exoplanets, ranging from very young, still-accreting planets detected at H-alpha, to older temperate planets which will be characterized using reflected starlight. First light was in Dec, 2019, but subsequent commissioning runs were canceled due to COVID19. In the interim, MagAO-X has served as a lab testbed. Highlights include implementation of several focal plane and low-order wavefront sensing algorithms, development of a new predictive control algorithm, and the addition of an IFU module. MagAO-X also serves as the AO system for the Giant Magellan Telescope High Contrast Adaptive Optics Testbed. We will provide an overview of these projects, and report the results of our commissioning and science run in April, 2022. Finally, we will present the status of a comprehensive upgrade to MagAO-X to enable extreme-contrast characterization of exoplanets in reflected light. These upgrades include a new post-AO 1000-actuator deformable mirror inside the coronagraph, latest generation sCMOS detectors for wavefront sensing, optimized PIAACMC coronagraphs, and computing system upgrades. When these Phase II upgrades are complete we plan to conduct a survey of nearby exoplanets in reflected light.
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