arXiv subjects

Kyle Van Gorkom

Publications and source records attributed to Kyle Van Gorkom.

At least 19 recordsLinked to original sources

arXiv2026

The Lazuli Space Observatory: Architecture & Capabilities

The Lazuli Space Observatory is a 3-meter aperture astronomical facility designed for rapid-response observations and precision astrophysics across visible to near-infrared wavelengths (400-1700 nm bandpass). An off-axis, freeform telescope delivers diffraction-limited image quality (Strehl $>$0.8 at 633 nm) to three instruments across a wide, flat focal plane. The three instruments provide complementary capabilities: a Wide-field Context Camera (WCC) delivers multi-band imaging over a 35' $\times$ 12' footprint with high-cadence photometry; an Integral Field Spectrograph (IFS) provides continuous 400-1700 nm spectroscopy at R $\sim$ 100-500 for stable spectrophotometry; and an ExtraSolar Coronagraph (ESC) enables high-contrast imaging expected to reach raw contrasts of $10^{-8}$ and post-processed contrasts approaching $10^{-9}$. Operating from a 3:1 lunar-resonant orbit, Lazuli will respond to targets of opportunity in under four hours--a programmatic requirement designed to enable routine temporal responsiveness that is unprecedented for a space telescope of this size. Lazuli's technical capabilities are shaped around three broad science areas: (1) time-domain and multi-messenger astronomy, (2) stars and planets, and (3) cosmology. These capabilities enable a potent mix of science spanning gravitational wave counterpart characterization, fast-evolving transients, Type Ia supernova cosmology, high-contrast exoplanet imaging, and spectroscopy of exoplanet atmospheres. While these areas guide the observatory design, Lazuli is conceived as a general-purpose facility capable of supporting a wide range of astrophysical investigations, with open time for the global community. We describe the observatory architecture and capabilities in the preliminary design phase, with science operations anticipated following a rapid development cycle from concept to launch. [Abstract abridged]

astro-ph.IM↗

arXiv2026

No need to modulate: On-sky results of a Neural Network enhanced pyramid wavefront sensor and prospects for the ELTs

One of the main limitations of ground-based extreme adaptive optics systems (XAO) is the balance between the temporal and photon noise error. The unmodulated Pyramid Wavefront Sensor (uPWFS) promises significant gains in sensitivity over its modulated counterpart, but its practical use is limited by its linearity range. Nonlinear reconstructors provide a pathway to recover this dynamic range while preserving the sensitivity of the uPWFS, thereby reducing photon noise and improving contrast. We present the real-time implementation of a Convolutional Neural Network (CNN) reconstructor and show on-sky results with MagAO-X, demonstrating robust and stable correction across diverse atmospheric conditions. Significant gains over default operation are seen in the low and moderate Strehl regimes, while the performance is slightly degraded in the high Strehl regime. We diagnose this in simulation and mainly attribute this to a non-optimized training dataset for the high-Strehl regime, rather than a fundamental limitation of the approach. Furthermore, initial simulations of the NN-enhanced uPWFS for a downscaled version of the Extremely Large Telescope (ELT) show substantial gains for fast petal-piston control. These results demonstrate that NN-enhanced wavefront sensing is a viable technology for future high-contrast instruments.

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arXiv2026

Demonstration of simultaneous PIAA- coronagraphy and wavefront sensing using a single metasurface-based focal-plane optic

Controlling residual wavefront aberrations downstream of an extreme adaptive optics (ExAO) system is a major challenge in high-contrast imaging. These aberrations produce quasi-static speckles due to differences between the wavefront-sensing and science paths. Highly sensitive wavefront sensors, such as Zernike wavefront sensors (ZWFSs), are used to mitigate these non-common path aberrations. High-performing coronagraphs, such as complex mask coronagraphs (CMCs), are also implemented in the focal plane. Both perform better with lossless apodization such as phase-induced amplitude apodization (PIAA) optics. Metasurfaces can have chromatic responses, allowing a single focal-plane optic to have different functionalities in different wavelength bands. We demonstrate such an optic by manufacturing a hybrid metasurface designed to function as a CMC and a ZWFS in two intermediate-band filters in the H band, each with a fractional bandwidth of approximately 1\%. We show measured optical responses with phases of $\sim π/2$ at shorter wavelengths and $π$ at longer wavelengths between $1500$ and $1700,\text{nm}$. This would allow for wavefront sensing at the shorter wavelength of $\sim1500\,\text{nm}$ and coronagraphy at the longer wavelength of $\sim1700\,\text{nm}$. Additionally, we tested the mask on-sky with the MagAO-X instrument at the Magellan Clay 6.5 m telescope at Las Campanas Observatory, Chile. On-sky results show a contrast of $\sim 10^{-1}$ at a non-ideal wavelength of $\sim 1600\,\text{nm}$. This is comparable to simulated contrast curves using the measured optical responses around that wavelength. Finally, we evaluated the wavefront-sensing performance of the metasurface using the MagAO-X internal source at $1300\,\mathrm{nm}$. The measured reconstruction error is consistent with simulations of an ideal Zernike wavefront sensor, confirming its wavefront-sensing functionality.

astro-ph.IM↗

arXiv2026

Forward modelling coronagraphic images with a fully physical, differentiable digital twin of MagAO-X: first laboratory results

Post-processing of high contrast imaging data relies on an accurate model of the stellar point spread function (PSF). Current techniques build this model from the science images themselves, using observational diversity (e.g., angular, spectral or polarimetric diversity), which can cause self-subtraction of the companion signal and constrains the observing strategy. Telemetry-based forward modelling instead builds the stellar PSF model from wavefront sensor data that is already recorded during the observation. The wavefront sensor measures the coherent starlight and can therefore be used to create a PSF model that only models the stellar light and does not reproduce the incoherent light of a companion. We present a fully physical and differentiable digital twin of the focal plane low-order wavefront sensor (FLOWFS) and the coronagraphic science beam of the MagAO-X instrument, implemented in \texttt{dLux}, and calibrate it on laboratory data. When fitted directly to the science images, the model reproduces the coronagraphic PSF down to the photon and read noise floor of the data. When instead forward modelled from the FLOWFS telemetry alone, the residuals reach $6\times10^{-5}$ of the stellar peak at $5\ λ/D$, a factor of 5 below the raw contrast, with the remaining residual set by how well the wavefront estimate transfers from the FLOWFS branch to the science branch of the model. An injected companion at $5\ λ/D$ with a peak contrast of $10^{-3}$ is recovered without measurable self-subtraction. We discuss the model improvements currently under development and the path towards on-sky validation.

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arXiv2026

On-sky demonstration of self-learning predictive control with MagAO-X

Direct imaging of exoplanets is very tricky and requires extremely well corrected wavefronts. Especially low-order order modes are detrimental to the performance of coronagraphs at their inner-working angle. However, that is precisely where conventional AO systems have the highest residuals that are caused by servo-lag errors. This servo-lag error can be reduced with predictive control where the control anticipates the future state of the atmospheric disturbance. We use a self-learning model predictive controller based on the concepts from sub-space predictive control (SPC). We present a novel implementation of the SPC by using an online QR-decomposition based recursive least squares approach. This approach has now been used for self-learning control of vibrations on the MagAO-X instrument. We see on average an Strehl increase of 15 percent and a decrease of the jitter to 0.9 mas. I will discuss how we have implemented the controller and its on-sky perfomance.

astro-ph.IM↗

arXiv2026

The Roman Coronagraph Community Participation Program: pre-launch reference star list and impact of reference star properties on post-processing performance

The upcoming Roman Coronagraph will be the first high-contrast instrument in space capable of high-order wavefront sensing and control technologies, a critical technology demonstration for the proposed Habitable Worlds Observatory (HWO) that aims to directly image and characterize habitable exoEarths. The nominal Roman Coronagraph observing plan involves alternating observations of a science target and a bright, nearby reference star for both wavefront calibration and reference differential imaging post-processing. Reference star criteria for the most demanding coronagraph mode are restrictive, limiting the sample to only 40 candidates for which thorough observational vetting is needed to assess their suitability. Reference star properties such as resolved diameters, presence of circumstellar dust, and close point sources may also have more subtle impacts on post-processing efficacy that may inhibit final contrast performance. In this work, we describe the current progress of the CoronaGraph Instrument Reference stars for Exoplanets (CorGI-REx) observing campaign, a 300+-hour observing campaign that utilizes instruments from around the world to vet reference stars for high-order wavefront control suitability. We will present the pre-launch list of reference star candidates being utilized for the Roman Coronagraph Observation Phase constructed from a thorough analysis of high contrast and interferometric observations. We will also present the results of simulations investigating the impact of reference star resolved diameters and companions on post-processing performance. We conclude by discussing the importance of reference star selection for scheduling observations and optimizing contrast performance for the Roman Coronagraph along with implications for HWO coronagraph operations.

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arXiv2026

Comparing realtime optical gain measurement and methods on MagAO-X

A lingering technical challenge for pyramid wavefront sensors (PyWFS) is their change in response between calibration and correction residuals, a quantity known as optical gain (OG). Given the prevalent use of PyWFSs in current and planned high contrast adaptive optics (AO), understanding and reliably measuring OG for realtime control unlocks advanced correction and post processing techniques. The OG quantity as an unknown inhibits a system's ability to stably correct non common path errors, reconstructing wavefronts, and PSF reconstruction. This work compares kinds of optical gain measurement techniques on MagAO-X, a visible light extreme AO instrument on the 6.5m Magellan Clay telescope. We present a set of on-sky measurements of OG across three techniques: 1) An on-sky calibration that acquires OG per spatial mode, 2) realtime measurements of the instantaneous Strehl Ratio (SR) on the pyramid tip, and 3) realtime measurement of known, high-frequency probe signal on the WFS itself. We compare these on-sky results with performance diagnostics to asses how faithfully OG is returned. We conclude with future steps for active control of OG on MagAO-X.

astro-ph.IM↗

arXiv2026

The eXtreme Wavefront Control Toolkit: High-Contrast Imaging Instrument Control for Ground and Space-Based Coronagraphs

We present the eXtreme Wavefront Control Toolkit (XWCTk) instrument control software system developed for the MagAO-X extreme adaptive optics (ExAO) instrument. The XWCTk is built on a foundation of the ImageStreamIO (ISIO) / MILK / CACAO low-latency image processing and high dimensional control tool chain. Instrument control is managed with the Instrument Neutral Distributed Interface (INDI). The application framework provides configuration, logging, and distributed IPC with INDI and low-latency IPC with ISIO. On MagAO-X, every detector is a potential wavefront sensor capable of sending commands to three separate DMs. MagAO-X utilizes a distributed control system, where multiple computers each manage low-latency wavefront control tasks but are capable of coordinated control. Implemented algorithms include neural networks for nonlinear reconstruction at over 3 kHz. We have incorporated distributed raspberry pis for accelerometer data acquisition with low-latency streaming to the real-time computers for sensor fusion control. A core design principle of the XWCTk is that all data can be saved all the time. This includes full-rate WFS images, DM commands, as well as science data. To facilitate this we have implemented a custom lossless compression system capable of sustaining high data rates to disk. A python interface for scripting and experimentation, as well as a python application framework is provided which can be used for non-real-time tasks. Remote operations (e.g. from Tucson Arizona when the instrument is at LCO in Chile) are routine. The XWCTk is under continuous development for the MagAO-X instrument, and will be adapted for GMagAO-X, the planned first-light ExAO coronagraph for the Giant Magellan Telescope. XWCTk is the baseline for a space high contrast imaging instrument, and as such ongoing development is focused on automation for robust operation in flight.

astro-ph.IM↗

arXiv2026

Closed-loop Atmospheric Dispersion Correction for High-Contrast Imaging with MagAO-X

Incoming starlight is refracted as it enters Earth's atmosphere from the vacuum of space. The wavelength-dependence of atmospheric refraction causes elongation of the broadband PSF of ground-based telescopes, especially in the visible spectrum. The result is degraded image quality alongside reduced coronagraph light-blocking efficiency, both of which limit high-contrast observations. An atmospheric dispersion corrector (ADC) is a dispersive optic used to compensate for this effect. Current methods for dispersion compensation use analytical models to anticipate dispersion strength based on parameters such as site altitude and telescope zenith angle; however, dispersion strength is also dictated by a number of factors that cannot be measured, including instantaneous humidity, temperature, and pressure along the line of sight to the star. This leads to constant over- or under-correction of the true atmospheric dispersion by the ADC. In this work, we use the Magellan extreme adaptive optics system MagAO-X at Las Campanas Observatory to measure and correct residual atmospheric dispersion in real-time. The amount of residual dispersion is encoded in the orientation of satellite spots generated by using MagAO-X's deformable mirror as a diffraction grating. We have used these real-time measurements as feedback for closed-loop control of the ADCs on-sky at visible and NIR wavelengths, reducing residual atmospheric dispersion down to sub-mas/$μ$m levels. Active atmospheric dispersion correction on MagAO-X is a precursor to high-contrast imaging with Extreme AO for the upcoming Extremely Large Telescopes, where high-precision dispersion compensation will be required to image exoplanets in reflected light.

astro-ph.IM↗

arXiv2026

Visible-Light High-Contrast Polarimetry with MagAO-X: Characterization and Initial Results

MagAO-X is a visible-light extreme adaptive optics instrument on the 6.5 meter Magellan Clay Telescope, recently upgraded to enable high-contrast polarimetric differential imaging (PDI) in r', i', and z' filters. Polarimetry is a powerful technique for suppressing unpolarized starlight and isolating the faint, polarized signal scattered by circumstellar dust, but it demands precise calibration of instrumental polarization effects introduced by the telescope and instrument optics. We present an overview of the MagAO-X polarimeter and characterize its polarimetric response using a purpose-built polarization generator that injects light of a known polarization state. From these measurements, we fit a Mueller-matrix model of the instrument and quantify its polarimetric efficiency and instrumental polarization as a function of the k-mirror image rotator angle and observing filter. The initial characterization revealed significant, dynamic inefficiencies driven by the image rotator, motivating the deployment of a dual rotating quarter-wave plate (DQWP) compensator that dynamically reorients the input polarization to the instrument's eigenpolarization. Following installation of the DQWP, we measured an average increase in polarimetric efficiency of +17.5% (to 87.4%) and a reduction in instrumental polarization of -5.4% (to 8.3%) across all filters. Finally, we demonstrate the on-sky performance of the polarimeter with i' imaging of the debris disk around HR 4796, producing one of the closest inner-working-angle views of the bright, forward-scattering side of the disk. These results help pave the way for polarimeters on future extremely large telescopes such as GMT and ELT.

astro-ph.IM↗

arXiv2026

The Space Coronagraph Optical Bench (SCoOB): X. Dark zone maintenance

The Space Coronagraph Optical Bench (SCoOB) is a vacuum high contrast imaging testbed designed to demonstrate starlight suppression at optical wavelengths and obtain contrasts better than 10$^{-8}$ in a one-sided dark hole from 3 to 10 $λ/D$ using a vector vortex coronagraph (VVC) mask. Some of the recent efforts have been in testing dark zone maintenance (DZM) algorithms which are used to stabilize the contrast in the presence of wavefront drifts and allow for the long integration times required by exoplanet observations. In this work, we discuss the results from simulations with two DZM algorithms - linear dark field control (LDFC) and extended Kalman Filter-based (EKF) DZM. We also report preliminary results from the testbed with LDFC.

astro-ph.IM↗

arXiv2026

The Space Coronagraph Optical Bench (SCoOB): 11. Modeling and correction of chromatic aberrations

The space coronagraph optical bench (SCoOB) is a high contrast imaging testbed designed to demonstrate starlight suppression techniques at visible wavelengths in a space-like vacuum environment. Since the previous proceedings, the testbed has undergone major component upgrades, including a 100%-yield BMC Kilo-C deformable mirror, a black silicon pupil stop, and circular polarizers between wedged substrates. To assess the performance limits imposed by lateral chromatic aberration induced by refractive optical elements, we develop analytic and numerical tools to predict the broadband contrast. Additionally, we present the broadband contrast performance of the testbed using implicit electric field conjugation with multiple sensing bands for broadband control.

astro-ph.IM↗

arXiv2026

Design and modeling of an oblique incidence dichroic mirror for a high contrast imaging system

The proposed Habitable Worlds Observatory (HWO) aims to detect and characterize Earth-like planets around Sun-like stars from the ultraviolet to the infrared using high-contrast imaging. A dichroic mirror is a natural choice for splitting light between multiple wavelength channels in such a system, but the coating must introduce minimal polarization aberrations and chromatic wavefront errors (WFE) to avoid limiting contrast. We present the design of a long-pass dichroic mirror operated at a $7^\circ$ angle of incidence that provides high reflection in the short-wavelength band, high transmission in the long-wavelength band, and a sharp cut-on near 550~nm. A multilayer thin-film design process was used to meet these spectral requirements while reducing polarization aberrations and chromatic WFE sensitivity. Reflected phase optimization was also incorporated to reduce sensitivity to manufacturing-induced layer-thickness variations, which can produce wavelength-dependent WFE and degrade coronagraph performance. The resulting coating-induced WFE was propagated through simulations of a vector vortex coronagraph to assess contrast performance. Simulations predict dark-hole contrast residuals at the $10^{-12}$ level, indicating that the optimized dichroic mirror does not limit coronagraph performance.

astro-ph.IM↗

arXiv2026

The spectral energy distribution of YSES 1 b and its circumplanetary disc

Context. Direct imaging enables the characterisation of substellar companions on wide orbits. These objects provide a testbed for our formation theories; therefore, it is important to obtain accurate physical parameters for them. One of these objects is YSES 1 b. Aims. Our objective is to improve the spectral energy distribution (SED) modelling of YSES 1 b and determine the bulk and atmospheric parameters. Methods. We obtained observations in the r', i', and z' bands using MagAO-X on the 6.5 metre Magellan Clay telescope at Las Campanas Observatory. We combined this data with archival VLT/SPHERE and VLT/NACO data and used a forward modelling approach to estimate the physical parameters. We tested models both without and with a circumplanetary disc (CPD) model. We represented the CPD by including a dust extinction model and a blackbody radiation component. Using the derived bolometric luminosity, we estimated the mass of YSES 1 b by fitting evolutionary models. Results. Including the CPD model provides a significantly better fit to the photometric data, yielding an object that is considerably warmer (2854+110-94 K vs 1727+172-127 K) and smaller (1.58+0.06-0.07 RJ vs 3.0+0.2-0.7 RJ) than previous estimates. The newly determined radius suggests that the addition of dust extinction could resolve the large radius anomaly identified previously. Depending on the age of the system, the estimated mass increases from 14+-3 MJ (17 Myr) to either 25.7+4.1-3.6 (17 Myr) or 41.6+3.6-3.4 MJ (27 Myr). Conclusions. Dust extinction and blackbody radiation from a CPD can substantially change the estimated physical parameters of an object. For YSES 1 b, this moves it into the brown dwarf regime.

astro-ph.EP↗

arXiv2025

Progress toward a demonstration of high contrast imaging at ultraviolet wavelengths

NASA's Habitable Worlds Observatory (HWO) aims to achieve starlight suppression to the $10^{-10}$ level for the detection and spectral characterization of Earth-like exoplanets. Broadband ozone absorption features are key biosignatures that appear in the 200-400nm near-ultraviolet (UV) regime. Extending coronagraphy from visible wavelengths to the UV, however, brings with it a number of challenges, including tighter requirements on wavefront sensing and control, optical surface quality, scattered light, and polarization aberrations, among other things. We aim to partially quantify and address these challenges with a combination of modeling, high-resolution metrology to the scales required for UV coronagraphy, and ultimately a demonstration of UV coronagraphy on the Space Coronagraph Optical Bench (SCoOB) vacuum testbed. In these proceedings, we provide a status update on our modeling and contrast budgeting efforts, characterization efforts to understand performance limitations set by key optical components, and our plans to move toward a demonstration of UV coronagraphy.

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arXiv2025

Optical design and polarimetric performance of a SmallSat UV polarimeter to study interstellar dust: PUFFINS

The Polarimetry in the Ultraviolet to Find Features in INterStellar dust (PUFFINS) is a SmallSat mission concept designed to obtain ultraviolet (UV) spectropolarimetric observations to probe the interstellar dust grain properties and to understand wavelength-dependent extinction and star formation. PUFFINS plans to observe 70 UV bright target stars at varying distances within a 180-320 nm wavelength range with 0.02% polarimetric accuracy. PUFFINS uses a simple telescope design with all reflective optics coated with protected aluminum to enhance reflectivity in the UV. The telescope and the spectropolarimeter, which consists of a Wollaston prism and a half-wave retarder, have been carefully selected to be greater than Technology Readiness Level 6 (TRL6). The telescope is designed to exhibit negligible instrumental polarization and crosstalk, significantly reducing the time needed for polarimetric calibration in orbit. The optimum and careful selection of the target stars will enable PUFFINS to observe an expanded and well-defined sample to test the predictions by interstellar grain alignment theory in the observation phase of 9 months. This paper outlines the details of the optical and optomechanical design and evaluates the polarimetric performance of PUFFINS.

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arXiv2025

The Space Coronagraph Optical Bench (SCoOB): 6. demonstration of Lyot low order wavefront control combined with high order wavefront control using a vortex coronagraph

To reach and maintain high contrast levels, coronagraph instruments will require a combination of low-order and high-order wavefront control techniques to correct for dynamic wavefront error. Efficient low-order wavefront sensing and control (LOWFSC) schemes use the starlight rejected by the coronagraph such that LOWFSC can operate with a relatively bright signal to correct rapid disturbances. Meanwhile, a family of high-order wavefront sensing and control (HOWFSC) techniques utilizing the science camera have been developed to create regions of high contrast known as dark holes. These two control loops must operate simultaneously for dark holes to be maintained over long observation periods. Using a 952 actuator MEMS deformable mirror and a vector vortex coronagraph (VVC) on the Space Coronagraph Optical Bench (SCoOB), we demonstrate a Lyot-based LOWFSC loop operating in combination with a HOWFSC loop. For these experiments, implicit electric field conjugation (iEFC) is the chosen HOWFSC technique, and we demonstrate how this empirical method can be calibrated and deployed while the LOWFSC loop corrects for dynamic wavefront error. We show this combination of LOWFSC and iEFC maintained 1E-8 contrast levels in air.

physics.optics↗

arXiv2025

The Space Coronagraph Optical Bench (SCoOB): 7. design, fabrication, and first light for a self-coherent camera

The 2020 Decadal Survey on Astronomy and Astrophysics tasked future space observatories with the goal of detecting and characterizing a large sample of Earth-like exoplanets. To achieve this, these observatories will require coronagraphs and wavefront control algorithms in order to achieve $10^{-10}$ or better starlight suppression. The Space Coronagraph Optical Bench (SCoOB) is a vacuum compatible testbed at the University of Arizona which aims to advance and mature starlight suppression technologies in a space-like environment. In its current configuration, SCoOB is a charge-6 vector vortex coronagraph outfitted with a Kilo-C microelectromechanical systems deformable mirror capable of achieving sub-$10^{-8}$ dark hole contrast at visible wavelengths using implicit electric field conjugation (iEFC). In this work, we demonstrate the use of a self-coherent camera (SCC) for dark hole digging and maintenance on SCoOB. The SCC introduces a small off-axis pinhole in the Lyot plane which allows some starlight to reach the focal plane and interfere with residual speckles. This enables high-order focal-plane wavefront sensing which can be combined with active wavefront control to null the speckles in a specified region of high contrast known as the dark hole. We discuss considerations for implementation, potential limitations, and provide a performance comparison with iEFC. We also discuss the design optimization and fabrication process for our SCC Lyot stops.

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